Pollution Prevention in
Metal Painting and Coating Operations:
          A Manual for Technical Assistance Providers

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Poll giipn -:. Pre ve nti o n
In Metal Painting and
      ng
A Manual for
Pollution Prevention
Technical Assistance Providers
April 1998

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Printed.on Recycled Paper

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 Acknowledgments
 NEWMOA is indebted to the US. Environmental Protection Agency's Office of Pollution Prevention
 for its support for this project. The Northeast states provided additional in-kind support.

 NEWMOA would also like to thank those who provided advice and assistance^ especially those who
 volunteered on the peer review committee:          •"          .           •

 Alan Buckley, Massachusetts Office of Technical Assistance
 Mike Callahan, Jacobs Engineering Group Inc        ,      .
 Dean Cornstubble, Research Triangle Institute                      ...
 Lynn Corson, Ph.D., Purdue University       .
 •Mike Eck, U.S. Army Environmental Center
 Tim Greiner, Gre.iner Environmental                                .
 PaulPagel,MnTAP            .
 Jeff Palmer, The Powder Coating Institute                 ;
 Alice Pincus, Pineus Associates
 Paul Randall, U.S. EPA '
 Alexander Ross, RadTech                        ,
 Mike Simek, Rutgers
 Rodger Taibert, Chemical Coaters Association International
 David Liebl, Solid and Hazardous Waste Education Center         '         /
 Kathy Blake,:New Hampshire Department of Environmental Services


  Project Staff/Contributors

 Terri Goldberg, NEWMOA P2 Program Manager—-Editor/Manager
 Lisa Regenstein, NEWMOA P2 Project Manager—Research/Writer
 Jennifer Shearman, NEWMOA Technical Staff—Research/Writer
  Beth Anderson, EPA—EPA Project Manager ,          .
'  Laurie Case, WMRC—Layout and Desktop Publishing         :         :
                            Printed on Recycled Paper

        Cover Photo courtesy Dean Cornstubble, Research Triangle Institute
  NEWMOA welcomes users of this manual to cite and reproduce sections of it for use in providing assis-
  tance to companies. However, the Association requests that users cite the document whenever reproducing.
  orquoting^o that appropriate credit is give to original authors, NEWMOA and U.S. EPA. NEWMOA
  thanks you for cooperating with this request.
                 .   ' -             -       •        •         .            /
   ".'"''    '•••-..'.-•     ,  '  in'  ""'"-.'    :  .•     • •  '       '••-••'

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Northeast Waste Management  Officials1  Association

The Northeast Waste Management Officials' Association (NEWMOA) is a non-profit, nonpartisanj  .
interstate governmental association. The membership is composed of state environmental agency
directors of the hazardous waste, solid waste, waste site cleanup and pollution prevention programs in
Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont.

NEWMOA's mission is to help states articulate, promote, and implement'economically sound regionaj
programs for the enhancement of environmental protection. The group fulfills this mission by providing
a variety of support services that facilitate communication and cooperation among member states and
between the states and EPA, and promote the efficient sharing of state and federal program resources.

NEWMOA was established by the governors of the New England states as an official interstate regional
organization, in accordance with Section 1005 of the Resource Conservation and Recovery Act
(RCRA). The organization was formally recognized by the U.S. Environmental Protection Agency
(EPA) in 1986. It is funded by state membership dues and EPA grants.
NEWMOA established the Northeast States Pollution Prevention Roundtable (NEP2 Roundtable) in
 1989 to enhance the capabilities of member state environmental officials to implement effective source
reduction programs. The NE P2 Roundtable's program involves the following components: (1) manag-
ing a regional roundtable of state pollution prevention programs; (2) publishing a newsletter; (3) manag-
ing a resource center of books, reports, case studies, fact sheets, notices of upcoming meetings and
conferences, and a list of P2 experts; (4) organizing training; and (5) conducting research and publishing
reports and other documents. The resource center provides pollution prevention information to state and
local government officials, the public, industry, and others. Funding for theNE P2 Roundtable is
provided by the NEWMOA member states and the U.S. EPA. For more information contact: Terri
Goldberg, NEWMOA, 129PortlandStreet,6thfloor,Boston,MA02114,(617)367-8558x302
(Phone); (617) 367-0449 (Fax); newmoa@aol.com (e-mail).                    '      :;"
                                            IV

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 About This Manual
 The Northeast Waste Management Officials' Association (NEWMOA) designed this manual to provide
 environmental assistance staff with a basic reference on the metal coatings process. The purpose of the
 manual is to enable assistance providers to rely on a single publication to jump start their research on
 pollution prevention for companies with which they are working. The manual is explicitly designed to be
 useful to assistance professionals with experience working with metal coating operations and those who
 have never before encountered this process. The U.S. Environmental Protection Agency Pollution
 Prevention Division funded this manual as a model of a comprehensive packet of pollution prevention
 (P2) information on a single industry.
 The Northeast Waste Management Officials' Association designed this manual to provide information
 on P2 methods for paints and coatings processes. Specifically, the manual focuses on P2 methods for
 reducing volatile organic compounds (VQCs) emitted during the coating of metal substrates. This
 manual stresses the use of low-VOC paints and coatings (i.e., high-solids, waterborne and powder
 coatings that contain lower solvent concentrations than conventional paints) as well as techniques that
 can increase transfer efficiency (i.e., the percentage of paints actually put on the part compared to the
 amount of paint used/sprayed). Methods for reducing the amount of solvents used during other stages
 of the coatings process, particularly surface preparation and equipment cleaning, also.figure prominently.

 NEWMOA collaborates with state and local environmental assistance programs in the Northeast; these
 programs have requested this manual to help them provide more efficient and effective help to the    .
 numerous companies with metal coating operations. Assistance providers have reported frustration with
 having to search databases for materials only to obtain a list of citations and case studies that they have
 to spend  considerable time finding in order to provide information to their client companies. In addition,
 these officials rarely have the opportunity to check the accuracy of the information they find in data-
 bases to determine whether the material is still current. To avoid duplicating efforts and to ensure that
 the information companies receive is up-to-date and accurate, NEWMOA developed this manual as a
 model "synthesized" information packet that includes an exhaustive compilation and synthesis of
 existing materials oh P2 for the metal coatings process.

 To compile this manual, NEWMOA reviewed many books,"articles,- fact sheets, reportsand guides on
 P2 for metal coatings operations. NEWMOA staff also sent a draft of the manual to more than 15
 expert reviewers for their comments and suggestions. The result is an up-to-date compilation of infor-
 mation on P2 options for metal coatings. However, pollution prevention is a rapidly changing field, and
 all users should check with the various centers identified in Appendix A to determine whether any new
  information is available.       , -  „  •


  Overview of Manual
  This manual is broken down into nine chapters as described below. Supporting case studies, tables,
  figures and appendices are also provided.

  +   Chapter 1 provides background information on paints and coatings, including a discussion of the
      coatings process arid wastes generated.
  *   Chapter 2 presents an overview of federal regulations that affect coatings processes.

  *•   Chapter 3 provides specific information on the role of technical assistance providers in promoting
      pollution prevention.
• -' •*   Chapter 4 is an overview .of pollution prevention options for surface preparation, coatings applica-
      tion/curing and equipment cleaning.                             .         ;

  *•   Chapter 5 discusses surface preparation methods with an emphasis on reducing solvent use.

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 *  Chapter 6 presents alternatives to solvent-borne coatings, including high-solids, waterborne and
            powder coatings.

 +  Chapter 7 provides an overview of application techniques (i.e., spray painting and other methods)
    along with a discussion of transfer efficiency.

 «•  Chapter 8 presents information on curing methods.

 4-  Chapter 9 discusses alternatives to traditional equipment cleaning methods.

 «•  Appendix A presents information resources for coatings.                                •

 *'  Appendix B presents information on how to calculate VOC/HAP emissions.

 «•  Appendix C provides information on conducting an economic analysis of paint costs.

 *•  Appendix D presents purchasing guidelines for HVLP spray guns.

 «•-  Appendix E presents information .on coatings testing.             .

 «•  Appendix F provides a glossary of terms pertaining to the coatings process.

 *  Appendix G provides information on calculating transfer efficiency.
  ,          .                               ,                                 !


 Audience
 NEWMOA designed this manual for individuals who are involved in providing technical assistance to
 firms seeking information on P2 for paint and coating processes. NEWMOA believes that the informa-
 tion in this manual also would be useful for environmental inspectors and permit writers who are
 involved in regulatory compliance activities. Comments and suggestions from manual users on content '
 and format are welcomed. Please take-a moment and complete the evaluation form included with this
 document to help us with future versions of this, manual and related manuals, or call NEWMOA at
 (617) 367-8558 to speak with us directly.


 Using This Manual
 This manual is designed to serve as a complete reference on P2 methods for paint and coating pro-
• cesses, however, it alone should not be used to advise companies on the selection of a particular coating
 system. The selection of a coating system depends on a number of application-specific factors, including
 the type of surface to be coated as well as the required perfotmancexharacteristics of the coating.
 Companies that decide to adopt an alternative system should do so only after consultation with the
 appropriate coating and equipment vendors, and careful in-house analyses of the costs and benefits as
 well as technical feasibility of the alternative system.


 Disclaimer
 The views expressed in this report do not necessarily reflect those of NEWMOA, NEWMOA member
 states, Waste Management and Research Center (WMRC), or U.S. EPA. Mention of any company,
 process, or product name should not be considered .an endorsement by NEWMOA, NEWMOA mem-
 ber states, WMRC, or U.S. EPA.
                                              VI

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 Table  of   Contents
 Acknowledgments
,i
 Chapter 1:  Background ...................................	v...........	...... 1

 Definition of Terms'...:	....;	...........	......	;.-	1.
 Uses for Paints and Coatings	••-••••	•	 1
 Paint Composition........	••	:..-2-
 Description of Coatings Processes..............	..,-	••	•••	•-	-2
 Examples of Typical Systems	.............	...4
 .Sources of Wastes	.......................:	..........4
 Summary.	-.	..•	 6

 Chapter 2:  Regulatory Overview.........	....:.;.7
 Clean Air Act.....	.........!	....	..	  8
 Resource Conservation and Recovery Act	  9
 Clean Water Act.......:................:	•-	...;.......,....	-12.

 Chapter 3:  Planning Pollution Prevention  Programs at Coating
 Facilities[[[	........:............	  15
 Characterizing a Facility...........	'.........................	•	-15
 Planning	.......	•••	'•.'—,	•••••	••—-•	 16
 Identify Pollution Prevention Opportunities .....—	'.	,........;	 22
        *                  •     ,        --•••'            ..„     . :            • ~    l~\ f~\
 Analyze and Select Options'...	...;	 ^
• Pilot Test or Validate Preferred Options.........,!........	•	•••••-.-	23
                                                                             •      '  ' O Q
 Procure and Implement New System	;	-..•	•	•••	-•	'••••••• ^J
 Evaluate and Keep the Program. Going	.-.'...,	':..„...... 23 ;

 Chapter 4: Overview of  Pollution Prevention  in  Coatings
 Application Processes	-25

  Chapter 5:  Surface Preparation	v.	 29
     '                  "   •   •     "• •         •               •-••-..-•          '99
 .General Description ......;.....,..,;..	••	 47
 ' Pollution Problem .,......;.,.,.............,....	/........-................:	..-,	••••• 29
  Mechanical Cleaning	.....:.,.;.	.,	.........;:	 /V
 • Chemically-Assisted Cleaning .....'.:	•	•	 30
  Stripping	.,	,	••••	-	•	•_	••	....... = ...-.•	 o^
  General P2 Options for Surface Preparation	.......,...:.....,..	.•••	•-.-	 30
  Qeaning	:.........	..','•	'•	••	•'	-•••••••:••••,	•••••
  Alternative Cleaning Methods ..."...	....."-	,••	•••••;	 od

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Chapter  6:  Alternatives to Solvent-Borne  Coatings	57
Conventional Paint Composition	".	57
Switch to Surface-Free Coating	'61
Alternative Coatings	•	61
High-Solids  Coatings	,	-	•	62
Waterborne  Coatings	,	'.••••	66
Powder Coating	'69
Radiation Curing..	'	• • 75
Emerging Technologies	,	-79

Chapter  7:  Application Techniques	.83
General Description of Spray Systems	-...	83
Pollution Problem	,	..83
General P2  Options	'	'.	-	--83
Strategies to Improve Transfer Efficiency	85
Conventional Air Spray (LVHP)	.-	88
High-Volume/Low-Pressure (HVLP) Air Spray i	89
Low-Pressure/Low-Volume (LPLV)	91
Airless Spray	•.	91
Electrostatic Spray	,	93
Other Methods	........'....	.95
Paint Booths...;	.-..-	:	-101

Chapter  8:  Curing  Methods....	109

Chapter  9:  Equipment  Cleaning	113

General Description	 113
Pollution Problem '.	'	'..	  1 1 3
P2 Options.^	:...	-.	'....	  11.3

References	 117
Appendix A	123
Appendix B	 127
Appendix. C	.............:	 129
Appendix D....'..	'......	•..'.	133
Appendix E	••• 135
Appendix F	 137
Appendix G	'. 149
                                    VIII

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 List of  Tables

 Table 1. Common Solvents, Federal Regulatory Status	v..	:	   7
 Table 2. Scheduled Date for MACT"Standards for Surface Coating ..	   9
 Table3. EPA Guidelines for Maximum VOC Content of Coatings ....'....	  10
 Table'4. Hazardous Wastes Generated from Coatings Operations	  13
 Table 5. Overview of Assessment Information	.....'	  20
 Table 6. Opportunities for .Improved Housekeeping in Coating Operations .:......	  26
 Table 7. P2 Options for Coatings Processes	.....:	  27
 Table 8. Alternatives to Chlorinated Solvent Cleaning	  35.
 Table 9.  Advantages  and'Disadvantages of Plastic Media  Blasting	\	43
 Table 10. Advantages and Disadvantages.of Vacuum Sanding. Systems...	.-..	  44
 Table 11. Advantages and Disadvantages of Sodium Bicarbonate	  46
 Table 12. Advantages and Disadvantages of Wheat Starch Blasting	.........;..  47
 Table 1 3. Advantages and Disadvantages.of Carbon Dioxide Blasting	.-.=-...  50
 Table 14. Advantages and Disadvantages of Sponge Blasting Systems	•	  51
' Table 15. Advantages and Disadvantages of Water Blasting Systems .................:...  52
 Table 1 6. Advantages and Disadvantages of  Fluidized Bed Stripping	....,..:.  53
 Table 1 7. Overview of Alternative Surface Preparation Technologies...:	  55
 -Table 18. Health Effects of Solvents Used in Paint Formulations,.	  58
 Table 19, Overview of Alternatives to Solvent-Borne Coatings :...:.,-..:...	.....	  63-
 Table 20. Advantages and Disadvantages of  High-Solids Coatings	  66
 Table 21. Advantages and Disadvantages of Waterborne Coatings	  70
 Table 22.  Characteristics'of Powder Coating Techniques......	  73
 Table 23. Advantages and Disadvantages of  Powder Coatings	....  75
 Table 24. Summary of Powder Coating Resin  Properties	  77
 Table'25. Advantages and Disadvantages of  Radiation-Cured.Coatings..	  79
 Table 26. Advantages and Disadvantages of  VIC	'	-	•••	••  80,
 Table 27. Advantages and Disadvantages of  Unicoat Paint Technology ...v.i:	  81
 table 28. Cost/Benefit Summary for Spray Application.Methods	...,...,...:....  87.
 Table 29. Advantages and Disadvantages of  HVLP Spray Guns—	'..'.	  90
 Table 30. Advantages and Disadvantages of  LPLV Spray Guns....	  91
 Table 3.1. Advantages and Disadvantages of Airless Spray Systems,.	  93
 Table 32. Advantages and Disadvantages ol  Electrostatic Spray Guns	  95
 Table 33. Advantages and.Disadvantages of  E-Coat Systems ......:	:;., 96
 "Table 34.  Advantages and Disadvantages of Autodeposition Systems...	  97
 Table 35.  Advantages and Disadvantages of Dip Coating Systems	,	  97
 Table 36.  Advantages and Disadvantages of Flow Coating Systems	,  98
 Table 37..  Advantages arid Disadvantages of Curtain Coating Systems	•-.-	'.-.   98
 Table 38.  Advantages and Disadvantages of Roll Coating Systems	   99
 Table'39.  Advantages and Disadvantages of Plural Component     •      '  •
            Proportioning Systems 	;...."...............	••	•••	100
  Table 40.  Advantages and Disadvantages of-Supercritical Carbon Dioxide-...:....	.100
  Table 41.  Transfer Efficiencies of Various Application'Technologies ...:.......	•• 101
  Table 42.  Overview of Application Technologies.....:.....	-	-.- 102
  Table 43.  Advantages and Disadvantages of Dry Filter Booths	."..-	•	1 06
                                           IX

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Table 44.'Air/Force Dry Vs. Bake	'.	 109
Table 45. Typical RA'CT Limits for Miscellaneous Metal Parts Coating	 1 1 1

List of  Figures

Figure 1. Overview of the Coating Process	;	    3
Figure 2. Coating Process and Waste Generation	,,...••    5
Figure 3. Emissions vs. VOC Content	;	  62
Figure 4. Major Resin Fluidization Methods	  68
Figure 5. HVLP System	V	-....-  89

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   Background

 C imply stated—pollution prevention makes   .
 O.good business sense. Faced with the increasing.
 costs and liabilities associated with end-of-pipe
 pollution control practices, many companies are
 mming to pollution prevention as a cleaner, safer
 and more cost-effective alternative.,

 EPA defines pollution prevention as any practice-
 which reduces or eliminates the amount or toxicity
 of pollutants' entering the waste stream or the
 environment prior to recycling, treatment or
 disposal. Pollution prevention includes such
 techniques as modification or redesign of pro-
 cesses; reformulation or redesign of products;
 product substitution; raw materials substitution;
 and improved maintenance, housekeeping and
 operating practices (EPAj, p. v).

 Designed for technical assistance providers, this -
 manual focuses on pollution prevention techniques
 for reducing emissions of volatile organic con>
 pounds (VOCs) from paint and coating processes,
 including reducing the amount of solvents used in
 coating formulations as well as in surface prepara-
 tion and equipment cleaning. Most of the informa-
 tion contained in this manual relates to the coating
 of metal substrates used to manufacture metal
 containers, automobiles, machinery (including
 computers), metal furniture, appliances and other
 consumer goods.

 This Chapter presents the definitions of key terms,
 discusses uses for paints and coatings and pro-
 vides general information on paint composition  £
 and coatings processes. It also provides examples
  of typical coating systems and discusses the
  sources of wastes in the coatings process, includ-
" ing the specific pollution problems that are the
  focus of this manual;

   Definition  of Terms
   ;   .  '    '            • •  •      "•''•    '    j
   The following terms are used throughout the . j
 '  manual. These terms are often used to mean a_.
   variety of things. To clarify the use of the terms in
 this document, we have provided the following
 definitions.

 Coating: This term refers only to organic or
 polymer coatings and their associated application
 techniques. In other words, although metal plating
 does perform the function of a coating (e.g., it
 improves appearance, corrosion resistance,
 abrasion resistance, and electrical or optical
7 properties), this manual does not cover metal
 "plating (i.e., zinc, aluminum, etc.) or related
 processes (i.e., electroplating, conversion coating,
 sputtering, ion plating, and plasma spraying).
 Detailed information on P2 options for metal
 plating can be found in NE WMO A's manual
 Pollution Preventionjor the Metal Finishing
 Industry.               ,
 Solvent: This term generally refers to hydrocar-
 bon-based or organic solvents only; that is,
 solvents made from petroleum that contain the
 chemical elements hydrogen and carbon. In other
 wordSj although water is a solvent in terms of
 function (i.e., it is a liquid capable of dissolving
 another substance); the use of the term  solvent in
 this manual, for the most part, does not apply to
 water or other non-carbon compounds.

  Uses  for Paints and

  Coatings

  Paint is a generic term typically used to identify a
  wide range of surface coating products, including
 conventional solvent-borne formulations, var-
  nishes, enamels, lacquers and water-based sys-
  tems. Normally, painting is a process where a
  liquid consisting of several components, when
  applied, dries to athin plastic film. Traditionally,
  major constituents of these paints are solvents.
  However, non-liquid paints such as powder
  coatings and high solids paints have also been  .
  developed. These newer materials have led to the
  use of the term coating instead of/the term paint.
  In general, the function of all paints and coatings
  is to provide an aesthetically pleasing colored and/

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Chapter 1: Background
or glossy surface, as well as to help metal and
other substrates withstand exposure to both their
environment and everyday wear and tear (TURIb,
P-1).

Paints and coatings can be categorized according
to their use into three major groups:

* Architectural coatings include all shelf goods
  and stock type coatings that are formulated for
  normal environmental conditions and general
  applications on new and existing structures.
  These coatings include interior and exterior
  house paints and stains, as well as
  undercoaters, sealers and primers.

* Product coatings are paints sold to and used
  by original equipment manufacturers (OEM).
  Paint consumers in this sector include produc-
  ers of wood furniture and fixtures, metal
  containers, automobiles, machinery, metal
  furniture, metal coil, appliances and other
  consumer goods.

* Special purpose coatings are used in automo-
  bile and machinery refinishing, high-perfor-
  mance maintenance, bridge maintenance,
  traffic  paint, aerqsol applications and other
  similar operations (TURIb, p. 1).
 Coatings Sales

 In 1995, sales by paints and coatings manu-
 facturers were $15.9 billion. Architectural
 coatings accounted for 38% of total surface
 coating shipments, product coatings for 33%,
 and special purpose coatings for 19%.
 Miscellaneous paint products made up 9% of
 the sales (NPCA). Most of the architectural
 coatings sold are water-based (73%), while
 the overriding majority of product and special
 purpose coatings were still conventional
 solvent-borne systems  (TURIb, p. 1).
The intent of this manual is to provide information
on polludon prevention opportunities for users of
product coatings. Because product coatings are
used by a wide variety of industries, it is difficult
to accurately quantify these users. In addition, the
use of product coatings occurs not only in OEM
settings, but.also in contract job shops. The
pollution prevention opportunities identified in this
manual are not industry specific, but rather they
include general options available to a variety of
firms that coat metal substrates. Therefore, many
of the P2 opportunities identified in this manual
can be applied to users of architectural and
special-purpose coatings as well.

Paint Composition

The major components of solvent-borne paints
and coatings are solvents, binders, pigments, and
additives. In paint, the combination of the binder
and solvent is referred to as the paint "vehicle."
Pigment and additives are dispersed within the
vehicle (IHWRIC, p. 2). The amount of each
constituent varies with the particular paint, but
solvents traditionally make up about 60% of the
total formulation. Typical solvents include toluene,
xylene, MEK, and MIBK. Binders account for
30%, pigments for 7 to 8%, and additives for 2 to
3% (KSBEAP, p. 4). Environmental issues
surrounding paints usually center around solvents
and heavy metals used in the pigments. Binders
and other additives can also affect the toxicity of
the paint depending on the specific characteristics
of the paint. For more information on paint
composition, refer to chapter 6.

Description of

Coatings Processes

The coating of metal substrates can be broken up
into three major steps: surface preparation,.a two-
step paint application/curing process and equip-
ment cleaning. These steps are presented in figure
1.            •-,                  '

Surface  Preparation

Although each of these steps can affect the
performance of the final finish, proper surface
preparation is essential.in ensuring the success of a
particular coating. In fact, as high as 80% or more
of all coating adhesion failures can.be directly
attributed to improper surface preparation
(Binksbj-p. 1).

In surface preparation, a variety of methods are
used to remove soils or other imperfections from
substrates, creating a surface that bonds well with

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                                                                      Chapter 1 • Background
Figure 1. Overview of the Coating, Process
Cleaning/
Surface
Preparation
fc

Application:
Spray or Dip
•. .
                                                    Curing:
                                                    Air dry or
                                                    Oven
                                          Stripping:
                                          Racks-or
                                          Rejects
                               Inspection:
 the coating. The most common form of debris are
 oils and/or greases that originate from mechanical
 processing or oils and greases that are deliberately
 applied for temporary storage or shipping (Kuhn,
 p. 25). Other contaminants commonly include
 oxidation, rust, corrosion, heat scale, tarnish, and
 smut (SME, p. 27-1). In some cases, old paint
 must also be removed prior to the application of a
 new paint coat (MnTAP, p. 2). Traditionally,
 halogenated solvents have been used as cleaning
 and stripping agents to remove these substances.

 As part of surface preparation, a conversion
 coating might be applied to improve adhesion,
 corrosion resistance, and thermal compatibility.
 The processes used most often for the application
 of conversion coatings on metal are phosphating
 (using iron or zinc) and chromating. Anodizing
 (i.e.,.the electrochemical deposition of an oxide
 coating) is sometimes used on aluminum surfaces
 (KSBEAP,p.2-3).      '.'••'

 In the phosphating process, acid attacks the metal
 surface, forming a microcrystalline layer that
 improves the surface for paint application.-Zinc
 phosphate coatings are predominately used for
 ' metal substrates (Doren et al., p.  131). Combining
 cleaning and phosphating in a single solution is  -
 possible; however this is not the case with zinc
 phosphating (KSBEAP, p. 2-3). For more infor-
 mation on conversion coatings consult, Pollution
 Prevention for Metal Finishing: A Manual'for
• Pollution Prevention Technical Assistance
Providers, published by the Northeast Waste
Management Officials'Association.

Coatings Application

Following surface preparation, paints and coatings
are applied to substrates using.a variety of meth-
ods, including:

* Dip coating] in which parts are dipped into
   tanks of paint and the excess paint is allowed
   to drain off;                          ,
«• Roller^ in which paint is rolled onto a flat part;
.-*• Curtain coating, flow coating;
 * Electrodeposition, in which a part.is coated by
   making it anodic or cathodic in a bath that is
   generally an aqueous emulsion of the coating;
 '  and
 * Various spray processes, in which paint is
   sprayed from a gun onto a part.

 Coatings are usually applied in a number of coats,
 starting with a prime coat followed by subsequent
 coats (basecoats and topcoats) and a finishing coat
 (clearcoats). Given the different types of coatings
 necessary to ensure adequate protection and
 performance, coatings should always be consid-
 ered as a system.

 Curing
 Once a paint has been applied, a curing process
 takes place that converts the coating into a hard,
 tough, and adherent film-. Coatings cure by

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Chapter 1: Background
chemical reaction or polymerization of the resins
(i.e., crosslinking). Mechanisms for initiating
curing generally include ambient temperature
oxidation, chemical reaction with another compo-
nent (two-component coating systems) or baking
in an oven. Radiation is an additional curing
mechanism (IHWRIC, p. 11).

Equipment Cleaning

The final stage of any coating operation is the
cleaning of equipment, such as spray guns and
hoses. This generally involves flushing solvent
through the coating system (Freeman, p. 483- .
484).

Examples  of Typical

Systems

Although the basic process remains the same, the
particular coating system, coating formulation and
application method used, can vary considerably
from industry to industry. In the automotive
industry, for example, approximately 80% of all
painting starts with an electrocoat primer, usually
applied by electrodeposition. Visible indoor areas
of automobile bodies receive a topcoat, usually of
the same color as the overall body topcoat. In
addition, the underside of the hood and inside of
the engine compartment usually receive a topcoat
of black alkyd or acrylic paint which is sprayed
on; therefore, they carry a two-coat system.
Outside surfaces of the body receive a sandable
surface coat, which is either fully or partially
sprayed and is applied on either the wet or
incompletely baked electrocoat. Next, the color
topcoat, usually an acrylic resin, is sprayed on and
baked. In many cases, a clearcoat is sprayed over
the color coat to provide "depth" (SME, p. 29-4-
6).

The appliance industry, however, uses high-solids
paints to spray coat surfaces. These paints are  •
hardened with a crosslinking agent called
melamine. Some assembled appliance cabinets .
receive a 7-stage zinc phosphate metal preparation
and are then prime coated inside and out by
electrodeposition. The cabinets can also be spray
primed with a thermosetting epoxy-resin-based
paint, followed by a topcoat of acrylic melamine
paint, which is sprayed on. Other appliances carry
 a powder coat, which is sprayed directly over the
 metal preparation, plus a decorative acrylic
 melamine coat (SME, p. 29-4-6).

 Steel furniture for indoor use generally receives a
 3- to 5-stage iron phosphate metal preparation,
 plus a dip, spray, or electrodeposited prime coat.
 The topcoat is usually an alkyd or acrylic. Steel
 outdoor furniture and steel doors usually receive a
 7- or 9-stage zinc phosphate treatment, plus a
 prime coat of epoxy-based spray paint or an
 electrocoat. The topcoats may be alkyds or
. polyesters, and are sometimes modified with
 silicone. In some cases, powder coats are applied
 over the iron phosphate preparation (SME, p. 29-
 7).            •

 Sources  of Wastes

 Traditionally, each step in the coating process
 • generates waste and emissions. Figure 2 presents a
 process flow diagram that outlines the sources and
 types of pollutants. Wastes occur in solid, liquid,
 and gaseous forms and can include the following:

 4 Scrubber water, paint sludge and filters from   •
   air pollution control equipment
 * Spent solvents, aqueous cleaners, wastewater
   and paint sludge from equipment cleaning
 * Aqueous waste and spent solvents from
   surface pretreatment
 + VOC emissions during paint application,
   curing and drying          ,     '
 * Empty raw material containers
 * Obsolete or unwanted paint (IHWRIC, p. 38)

 Inefficient paint transfer can be the largest source
 of waste and VOC emissions from paint and
 coating processes. Paint used but not applied to
 the surface being coated (e.g.,-paint overspray)
 generally becomes waste. A spray booth can be
 used to remove the overspray .as it is generated
 (IHWRIC, p. 38). However, the type of booth
  selected can also affect the volume and type of
  paint waste generated (MnTAP, p. 4). See chapter
  4 for more information on spray booths and their
  effect on waste generation.

  Evaporation of organic solvents is  an important
  source of air emissions. During coating applica-
  tion, solvents that are present in conventional

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                       ,        .".                                  Chapter 1: Background


  Figure 2.   Coating Process and Waste Generation (IHWRIC, p. 34)

 Inputs                          Processes                        Wastes
Abrasives
Solvents
Alkaline solutions
Water
 Paints
 Thinners
 Brushes
 Rollers
 Rags
 Solvents
 Alkaline Solutions
                              Raw Material Inventory
                                       I
Surface Preparation
  Paint Application
 Equipment Cleaning
                                  Spills
                                  VOCs    .
                                  Obsolete or leftover paint
Ground abrasive (e.g., sand.)
    mixed with metal fines.
Spent solvents
Alkaline solutions
Wastewater  .
Sludge  with metals
VOCs
Containers
 Paint scraps
 Paint sludge
 .Scrubber water
 Filters
 Rags, brushes, and rollers
 VOCs
 Containers
 Wastewater
 Spent solvents
 Paint sludge
 Alkaline solutions
 VOCs
 Containers
   paint formulations evaporate and release VOCs
   into the air (IHWRIC, p. 38). Emissions occur
   during initial coating, as well as each time a
   surface is recbated during the life of the object or
   structure (EPAk). In addition, solvents used to
   thin paint, to clean equipment, 'and to prepare
              surfaces for coating can be sources of VOCs
              (IHWRIC, p. 38)..

              Specific estimates of the amount of solvents
              released during coating application are difficult to
              make as use is spread across numerous industry

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 Chapter 1: Background
 groups. However, EPA has developed air emission
 factors for solvent losses from paint and coating
 applications. EPA estimates that all toluene and
 87% of the xylene isomers used in paints and
 cpatings are emitted to the atmosphere when the
 emissions are uncontrolled. No emission factors-
 are available for MEK and MIBK used in paints
• and coatings, but it can be assumed that, like
 toluene and xylene, virtually all these solvents are
 eventually released to the atmosphere (EPA, p.
 157-158).

 Cleaning of equipment is a third major source of
 waste generation. Generally, all paint-application
 equipment must be cleaned after each use to
 prevent dry paint residue and avoid contaminating
 batch processes. In addition, brushes and rollers
 must be cleaned after each use to remain pliable
 (IHWRIC, p.. 38).

 Summary

 The primary focus of this manual is on P2
 methods for reducing pollutants generated during
 coatings application and on reducing emissions of
 VOCs in particular. VOCs can pose risks to
 human health and the environment. These prob-.
 lems have prompted the federal government and a
 number of states to promulgate regulations to
 control releases of solvent emissions and wastes
 from paint and coating processes. For an overview
 of applicable regulations, see chapter 2.

 ' Pollution prevention is an effective method for
 reducing emissions of VOCs and other wastes,
 and therefore, for reducing a firm's regulatory
 compliance burden. General information on
 promoting pollution prevention can be found in
 chapter 3. An overview of specific P2 options for
  coatings processes is discussed in chapter 4, with,
  detailed technical information provided in chapters
  5-9. See table 7 at the end of chapter 4 for a
  complete list of P2 options.

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    Regulatory  Overview
   The use of solvents in coating formulations and '.,
   in other areas of the coating process poses a
number of risks, to human health and the environ-
ment. To reduce the risks resulting from exposure
to these substances, the federal government and
individual states have regulated the generation and
management of wastes from paint and coating,
operations. Applicable regulations dependon the
environmental medium to which the waste is
released (e.g., air, land, or water) and the regula-
tory status of the generator (IHWRIC, p.  10).
A discussion of individual state laws is beyond the
scope of this document. However, this chapter
provides an overview of the major federal statutes
'that affect coating processes, including the Clean
Air Act (CAA) and the Clean Air Act Amend-
ments of 1990 (CAAA), which regulate air
releases; the Resource and Conservation Recov^
eiy Act (RCRA), which regulates hazardous
wastes; and the Clean Water Act (CWA), which
regulates wastewaters. For an overview of the
regulatory status under the CAAA and RCRA for
particular solvents used in paint and coating
operations, see table 1 .Technical assistance
  Table 1. Common Solvents, Federal Regulatory Status (IHWRIC, p. 5)
Solvent
Aliphatic Hydrocarbons
Mineral Spirits ,
Aromatic Hydrocarbons
Toluene , '
Xylene
Esters
Ethyl Acetate .
Butyl Acetate
Ketones
Acetone
Methyl Isobutyl Ketone
Methyl Ethyl Ketone
Glycol Ethers
Monoethyl Ether
Alcohols
Ethyl Alcohol
Butyl Alcohol --
RCRA Hazardous
- ,Yes . .
Yes
Yes
Yes
. Yes
Yes
Yes
Yes
-No
Yes
, Yes
Air Toxics Program a
- m Maybe b .
Yes
Yes ;
No
No ,
N6C '.'....••
Yes
Yes . , '
. . No • '
- No
No
  0 Under the 1990 Clean Air Act Amendments.       •         .        •   '
  b Depends on the composition of the mineral spirits; some cheaper blends may contain'aromatic
  solvents such as benzene.                .        .          -.             .
 ; c Acetone has recently been delisted from the GAAA's Title III list of VOCs. However, technical
  assistance providers should not promote the use of acetone to achieve environmental compliance.
  Material substitution using acetone does not constitute a pollution prevention option.

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Chapter 2: Regulatory Overview
providers should check with their state regulatory
programs to see if their state has imposed require-
ments stricter than those developed under the
federal programs. Coating operations might also
be affected by a number of other federal and state
regulations. Many of these regulations are industry
specific rather than process specific.

Clean Air Act

The Clean Air Act and the Clean Air Act Amend-
ments of 1990 consist of 11 chapters or titles that
require EPA to establish national standards for
ambient air quality and to work with states to
implement, maintain, and enforce these standards.
Of these titles, none have attracted more attention
from industry than the Title IH air toxics program,
which brought many previously unregulated
companies and processes under legislative control
(Freeman, p. 34).,

Under Title III, EPA created a list of 189 hazard-
ous air pollutants (HAPs) of which 149 also are
VOCs. Surface coating operations of all kinds are
major users of these compounds. Commonly used
compounds include toluene, xylene, MEK and
MIBK. VOCs not regulated under the air toxics
program might be regulated under Title I provi-
sions for ozone non-attainment areas (Falcone, p.
35). Details of these titles are provided below.
  Air Releases from Coatings Processes

  *• VOCs, which contribute to ozone pollution
  * Heavy metal dust from pigments
  *• Atomized paint from spray applications
                           (IHWRIC, p. 10)
 Air  Toxics

 Under Title HI, facilities that emit HAPs are
 grouped into categories with similar operating
 processes, including the process of surface
 coating. Individual sources within a category are
 considered "major" if they emit or have the
 "potential to emit" 10 or more tons per year- of
 any HAP on the list or 25 or more tons per year'
 of a combination of HAPs. EPA defines "potential
 to emit" as the amount of emissions that a facility
 could release if it operated at maximum capacity
 24 hours per day, 365 days per year.
Under Title III, major sources are subject to
maximum achievable control technology (MACT)
standards. MACT standards specify the maximum
degree of reduction in the emission of HAPs that
must he met through the use of traditional control
technologies as well as through pollution preven-
tion techniques. EPA has listed 16 surface coating
processes as source categories subject to MACT
standards, although not all of these surface coating
processes apply to the coating of metal substrates.
MACT standards are to be promulgated according
to the schedule in table 2. Existing sources gener-
ally will have up to 3 years from the effective date
of the standards to comply.

Ozone

Under Title I, EPA established national ambient air
quality standards (NAAQS) to limit levels of
"criteria pollutants," including carbon monoxide,
lead, nitrogen dioxide, particulate matter, ozone,
and sulfur dioxide. The federal government has.
developed control technique guidelines (CTGs)
which deal with a number of sources of air
pollution in nonattainment areas (i.e., geographic
areas that did not meet the NAAQS). These
guidelines require the use of reasonably available
control technologies (RACT).

For surface coating sources, the federal CTGs
generally define RACT in terms of the VOC
content limits of a coating; that is RACT is the
 mass of VOC per unit volume of coating (minus
 water) as applied (ready for application). In some
 cases, however, RACT is defined in terms of the
 percentage emission reduction achieved with add-
 on control devices, equipment specifications,
 record keeping, reporting requirements, and
 exemption levels (EPAf, p. 2-1). While limits are -
 based on specific industry groups and applications,
 the VOC limit of 340 g/1 (2.81b/gal) can be consid-
 ered an unofficial national standard (Freeman, p.
 486). For more specific information on EPA
 guidelines for VOCs in coatings, see table 3.

 Other Requirements.

 Under Title V, the permitting provision of the
 CAAA, all major sources must apply for operating
 permits. Accurate information on source pollutants
 and emission quantities must be gathered before
 application submittal (Falcone, p. 35). Information
 about calculating VOC and HAP emissions from
                                              8

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                                                               Chapter 2: Regulatory.Overview
Table 2. Scheduled Date for MAC! Standards for Surface Coating (EPAm, p. 1 -5)
Source Categories
   Scheduled Date for
   Emissions Standards
Aerospace Industries   .           •  "
Auto and Light Duty Truck (Surface Coating)
Flat Wood Paneling (Surface Coating)
Large Appliances (Surface'Coating)
Magnetic Tapes (Surface  Coating)

Manufacture of Paints, Coatings,
and Adhesives
   10/8/96   .',            .
   11/15/00-        ,
   11/15/00
   11/15/00                  ;
   11/15/94 (final rule issued 12/15/96;
      compliance 2 or 3 years)   >
   11/15/00             ,
 Metal Can (Surface Coating) .
 Metal Coil. (Surface Coating)
 Metal Furniture (Surface Coating)
 Miscellaneous Metal  Parts and Products
 (Surface Coating)
 Paper-and Other Webs (Surface Coating)
   11/15/00
   11/15/00
   11/15/00
          11/15/00

   11/15/00
 Plastic Parts and Products (Surface Coating)  .
 Printing, Coating, and Dyeing -of Fabrics
 Printing/Publishing (Surface Coating)

 Shipbuilding and Ship Repair (Surface Coating

 Wood Furniture (Surface Coating)
   11/T5/00  '   '• ••:
          11/15/00. •   v  •
   11/15/94 (final rule  5/30/96;
       compliance 3 years)
   11 /15/94 (final rule  issued  12/15/95;
       compliance 1 year)
   9/7/95 (final rule issued 2/9/96;
       compliance  11/21/97)
 NOTE: Work is beginning on the development of the 2000 regulations. Meetings were held in April of
 1 997 and workgroups are organizing to further develop the regulations..
 coatings processes can be found in appendix B.
 State and local governments oversee, manage, and
 enforce much of the permitting program and many
 of the other requirements of the CAAA. For more
 information pertaining to the CAA, see 40 CFR
'Parts 50-99.          '        '  .'       .

 Resource
 Conservation and
 Recovery Act

 Under the Resource Conservation and Recovery
 Act Subtitle C, EPA has established a "cradle-to-
 grave" system governing hazardous waste. Most .
 RCRA requirements are not industry specific but
 apply to any company that transports, treats,
 stores, or disposes of hazardous waste. Wastes
generated during the application of paints and
coatings might be considered hazardous because
of the presence of solvents or toxic metals ,
(IHWRIC,p. iO).  .
 RCRA Wastes from Coating Processes

 * Organic solvents commonly used in paint
     formulations                   ,
 * Waste paint containing heavy metals
 * Materials used fprsurface preparation and-
   equipment cleaning (IHWRIC, p.: 12)
 Waste  Characterization

 A waste is considered hazardous if it is included
 on one of the four EPA lists of hazardous wastes;
 if it displays one or more of the characteristics of

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Chapter 2: Regulatory Overview
Table 3.  EPA Guidelines for Maximum VOC Content of Coatings (SWR, p. 46)
Process ;
Can Coating
* Sheet basecoat and overvarnish; iwo-piece can exterior
VTwo-, three-piece can interior body spray; two-piece
can exterior end
+Side-seam seal
+End sealing compound
Coil Coating
Fabric Coating
Vinyl
Paper
Aut.o and Light-Duty Truck
+Prime
^Topcoat
^Repair
Metal Furniture •
Magnet Wire
Large Appliance
Miscellaneous Metal Parts
Wood Paneling
^Printed interior
^Natural- finish hardwood'
*Class II hardwood
Limitation
(pounds per gallon)
2.0;' 2.8
3.6; 4.2 •
5.5
3.7
2.6
2.9
3.8
2.9 .
1.9
2.8
. ' 3.0
.3.0
1.7
2.8
0.4-4.4
1.7
3.2
2.7
 hazardous waste (ignitability, corrosivity, reactivity
 or toxicity); or if it is a mixture that contains a
 listed hazardous waste.

 *• Listed wastes include acutely hazardous
   commercial chemical products and toxic
   commercial chemical products, designated
   with the code "P" or "U," respectively; hazard-
   o.us wastes from specific industries/sources,
 •  designated with the code "K"; or hazardous
   wastes from nonspecific sources, designated
   with the code "F".

   F wastes are of particular interest to paint and
   coating operations because they are generic  •
   wastes commonly produced during coating
  application. Examples from this list include
  spent solvents used in cleaning and used paint
  thinners such as xylene and toluene (IVVRCb, p.
  15).

^Characteristic wastes include those that are
  ignitable, corrosive, reactive or toxic. Ignitable
  wastes have a flashpoint of less than 140°F •
  and are easily combustible or flammable.
  'Corrosive wastes have a pH of 2 or less, or of
  12.5 or greater and can dissolve metals or
  other materials. Reactive wastes are unstable,
  or undergo rapid or violent chemical reaction
  with water or other materials. Toxic wastes
  contain concentrations of heavy metals, certain
  solvents,  or pesticides rn excess of correspond-
                                             10

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                                                                     Chapter 2: Regulatory Overview
  ing regulatory parameters-determined by the
 • Toxicity Characteristic Leaching Procedure
  (TCLP). Characteristic wastes are designated
  with the ERA hazardous waste code "D," See ••;
  table 4 for more information on hazardous ,
  wastes generated from coatings operations.

Generator  Status

To determine what a facility must do to. comply
with RCRA requirements, the facility must first
determine its generator status. Generator status is
based on the amojunt of waste generated on a
monthly basis. The following criteria determine
the quantity of waste that is regulated by RCRA:

 1) material remaining in a production process is
 not counted as waste, until it is no longer being
• used in that process.

 2) waste discharged directly and legally to a
 POTW in compliance with CWA pretreatment
 standards is riot counted toward RCRA generation
 total.                      •'-.,'_•.

 3) any material that is characteristic or listed as a
 hazardous waste, and is accumulating after
 its removal from the process before being sent off
 site for treatment, storage, or disposal, is counted
 toward RCRA Subtitle C generation total-

 Facilities that generate hazardous waste are
 subject to certain waste accumulation, manifest-
 ing, and record keeping standards based on the
 amount of waste generated. RCRA specifies three
 •categories of waste generators. The following
 outlines the basic guidelines for generator status;
 be aware, however, that state guidelines may vary.

 + Conditionally exempt small quantity generators
   (CESQGs) generate less than 220 pounds of
   hazardous waste, or 2.2 pounds of acute
 .  hazardous waste (K wastes), per calendar
   .month. CESQGs cannot accumulate more
   than 2,200 pounds of nonacute hazardous
   waste.(or 1-kilogram, of acute hazardous
   waste).             '  .

 f Small quantity generators (SQGs) generate
   220 to 2,200 p9unds of hazardous waste per
   calendar month. SQGs cannot accumulate
  more than 13,200 pounds. Storage time is
  restricted to 180 days.'        .  -

* Large quantity generators (LQGs) generate
  more than 2,200 pounds of hazardous waste
  per calendar month. Storage time is restricted
  to 90 days.    '                    ,

Each state has varying degrees of regulation for ,
the three generator classes. At a minimum,
however, EPA requires each class to comply with
the following requirements:    ,

Large Quantity  Generators

+ Notify the US EPA or state and obtain an EPA  •
  ID number from the state regulatory agency
+ Store waste for no more than  90 days
'*• Comply with container standards and tank
  rules                 •         •   •  .
+ Prepare and  retain a written contingency plan
* Prepare and  retain a written training plan
  which includes information on the annual
•  training of employees
+ Prepare a written waste minimization plan
•* Dispose of hazardous materials only at a
  RCRA permitted site
* Only use transporters with EPA ID numbers
* Use proper Department of Transportation
  (DOT) packaging and labeling
«> Use the full Uniform Hazardous Waste Mani-
  fest          •        _..';,   -
*Placea 24-hour emergency number on-all
   manifests  ;
* Report serious spills or fires to the National
   Response Center       ,      '
•* Obtain a DOT registration number for ship-  .
   rrients over 5,000 pounds
 * Keep ail records for 3 years     :
 •* Make' sure that any treatment or recycling done
   onsite is permitted                       .  '
> Report missing shipments in writing
 •* Submit biennial reports of hazardous waste
   activities, including waste minimization       .

 Small Quantity Generators

 V Notify the US EPA or state and obtain  an EPA
   ID number from the state regulatory agency
 * Store  waste for no more than 1 80 days (270
   days if the waste is shipped more than 200
   miles)            .  "    •               ..
                                             11

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Chapter 2: Regulatory Overview
* Comply with container standards and tank
  rules
*• Dispose of hazardous materials only at a
  RCRA permitted site
* Only use transporters with EPA ID numbers
* Use proper Department of Transportation
 ' (DOT) packaging and labeling
+ Use the full Uniform Hazardous Waste Mani- '
 •fest
* Place a 24-hour emergency number on all
  manifests
* Post emergency response telephone numbers
  near telephones
* Provide informql employee training
*• Make sure that any treatment or recycling done
  onsite is permitted
«• Report missing shipments in writing
* Keep all records for 3 years

Conditionally Exempt Small Quantity
Generators
                               i
* Avoid accumulating more than 1,000 kilo-
  grams (2,200 pounds) of hazardous waste
  onsite at any one time
* Send waste to a facility that is at least ap-
  proved to manage municipal.or industrial solid
  waste

Toxics  Release  Inventory
 Reporting

 Some coating facilities may have to publicly report
 many of the chemicals they use under the federal
 Toxic Release Inventory (TRI) reporting require-
 ment. Facilities report information on a TRI data
 form (Form R) for each toxic chemical that is
 used over the threshold amount. Basic information
 that is reported in a Form R includes the follow-
.ing:                                .   .
 4-   Facility identification
 «•   Parent company information
 «•   Certification by corporate official
 *  ' SIC code
•4   Chemical activity and use information
 *   Chemical release and transfers
 *   Off-site transfer information
 +   On-site waste treatment
 *•   Source reduction and recycling activities

 The releases and transfers, reported on a Form R
 include the following:
* Emissions of gases or particulars to the air
* Wastewater discharges into rivers, streams,
  and other bodies of water
* Releases to land onsite including landfill,
  surface impoundment, land treatment, or other
  mode of land disposal
* Disposal of wastes in underground injection
  wells
* Transfers of wastewater to POTWs
* Transfers of wastes to other offrsite facilities for
  treatment, storage, and disposal

A facility must fill out Form R if it meets the
following criteria:

* The facility is included in SIC codes 20 to 39
* The facility has  10 or more full-time employees
* The facility manufactures, processes, or
  "otherwise uses" any listed material in quanti-
  ties equal to or greater than the established
  threshold for the calendar year

The manufacturing and processing thresholds
have dropped over the reporting years from
75,000 pounds in 1987 to 25,000 pounds in 1989.
For a chemical "otherwise used," the threshold
amount is 10,000 pounds. Technical assistance
providers can use TRI data to develop an aggre-
gate picture of the releases and transfers from a
facility.

Clean  Water  Act

The primary objective of the Federal Water
Pollution Control Act, cprnmonly referred to as
.the Clean Water Act (CWA), is to restore and
maintain the chemical, physical and biological
integrity of the nation's surface waters. Pollutants
regulated under the C WA are classified as "prior-
ity" pollutants. These include various toxic
pollutants; "conventional" pollutants, such as
biochemical oxygen demand (BOD), total sus-
pended solids (TSS), fecal chloroform, oil and
grease, and pH; and "non-conventional" pollut-
ants, including any pollutant not identified as
either conventional or priority.

National  Pollutant  Discharge
Elimination  System  (NPDES)

Under the CWA, most point sources of wastewa-
ter (e.g., discharge pipes or sewers) discharging to
 waterways require a National Pollutant Discharge
 Elimination System permit. Permits, issued by
                                            12

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                                                                    Chapter 2: Regulatory Overview
Table 4.  Hazardous Wastes Generated from Coatings Operations (EPAb,
           p. 96-97)
EPA Hazardous
Waste Number
Hazardous Waste
 D006 (cadmium)
 D007 (chromium)
 D008 (lead)
 D009 (mercury)
Wastes that are hazardous due to. the characteristic of toxicity for each of the
constituents.                 •    »                     •
FOOl
Hafogenatedso/vents used in degreasing: tetrachloroethylene, methylene
chloride, 1,1,1 -trichloroethdne, carbon tetrachloride, and chlorinated
fluorocarbons; all spent solvent mixtures/blends used in degreasing con-
taining, before use, a total of 1 0 percent or more (by volume) of one or
more of the above, halogenated solvents or those solvents listed in F002,
F004, and F005; and still bottoms.from the recovery of these spent
solvents and spent solvent mixtures.
 F002
 Spent halogenated solvents: tetrachloroethylene, methylene chloride, frichlo-
 roethylene, 1,1,1 -trichloroethane chlorobenzene, 1,1,,2-trichlorp-l ,2,2-
 trifluoroethane, ortho-dichlorobenzene, trichlorofluoromethane, and 1,1,2-
 trichloroethane; alUpent solvent mixtures/blends containing, before use, one
 or more of'the above halogenated solvents or those listed in FOOl, F004 ,
 F005; and still bottoms from the recovery of these spent solvents and spent
 solvent mixtures.               ,      .
 F003
 Spent nonha/ogenafed solvents: xylehe, acetone, ethyl acetate, ethyl ben-
 zene/ethyl ether, .methyl isobutyl ketone, n-butyl alcohol, cyclohexanone, and
 methanol; all spent solvent mixtures/blends containing, before use, only the
 above spent nonhalogenated solvents; and all spent solvent mixtures/blends
 containing, before use, one or more of the above nonhalogenated-solvents,
 and a total of 10 percent or more (by\ volume) of one of those solvents listed
 in FOOl, F002, F004, and F005; and still bottoms from the recovery of these
 •spent solvents and spent solvent mixtures.                    .
 F004
 Spenf ndnha/ogenafed solvents: cresols and cresylic acid, and nitrobenzene;
 all spent solvent mixtures/blends containing, before use/a total of 10 '  .
 percent or more (by volume) of one or more of the above nonhalogenated
 solvents or those solvents listed in .FOOl, F002, and F005; and still bottoms
 from the recovery of these spent solvents and spent solvent mixtures.   - )
  F005
 Spenf npnha/ogenafed so/vents: toluene, methyl ethyl ketone, carbon disul-
 fide, iso'butanol, pyridine, benzene, 2-ethoxyethanol, and 2-nitropropane; a
 spent solvent r.iixtures/blends containing,.before use, a total of 10 percent o
 more (by volume) of one or more of the above non-haldgenated solvents o
 those solvents listed in FOOl, F002, or F004; and still bottoms from the
 recovery of these spent solvents and spent solvent mixtures.
                                             13

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Chapter 2: Regulatory Overview
 Wastewaters from Coatings Processes

 * Wastewaters from equipment cleaning and
   surface preparation
 * Rinsing of a surface after paint removal
                          (IHWRIC, p. 1.1)
either EPA or an authorized state (EPA has.
presently authorized 40 states to administer the
NPDES program), specify levels of toxicity and
other characteristics that must be achieved prior to
discharge. Pretreatment of the wastewatef is
generally necessary. Wastewater generated-from
coating application might be regulated because of
the presence of organic solvents or heavy metals
(IHWRIC, p. 11).

Pretreatment Program

Another type of discharge that is regulated by the
CWA is one that goes to a publicly-owned treat-
ment works (POTWs). The, national pretreatment
program controls the indirect discharge of pollut-
ants to POTWs by industrial users. Facilities
regulated under this program must meet certain
pretreatment standards. The goal of the pretreat-
ment program is (1) to protect municipal wastewa-
ter treatment plants from damage that can occur
when hazardous, toxic, or other wastes are
discharged into a sewer system and (2) to protect
the quality of sludge generated by these plants.
For more information about the CWA, see 40
CFR Part 433.
                                            14

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  Planning  Pollution  Prevention
  Programs  at  Coating  Facilities
     How can assistance providers and regulatory
     compliance staff sell pollution prevention
 options to a facility? The most important point
 that an assistance provider can make is that
 pollution prevention can help the facility achieve
 regulatory compliance while saving money. The
 savjrigs associated with recapturing and reclaiming
 materials is obvious; but the value of reducing the
 regulatory burden and the expense from wasted
 raw materials, can, in many cases, exceed the cost
 of pollution prevention projects. Overall, the
 benefits associated with pollution prevention
 include:                            7

"•* Reduced Operating Costs/Overhead
 .  These savings can. result in reduced utility
   charges, water/sewer fees, wastewater treat-
   ment costs, wasfe disposal expenses, permit
   discharge fees, analytical monitoring,-and
   reporting costs.

 «• Reduced Manufacturing,Costs   ;  ,
   Facilities can save money on reduced material
   costs (paint and solvent purchases), water  -'
   costs, and energy costs.

 V Product Quality Improvements
 •  Pollution prevention techniques often increase
   the'quality of the coating process. Improving
   process controls makes coating operations
   more efficient and allows the;m to run within
   tighter operating parameters, often resulting in
   decreased reject rates.               ,

 , * Environmental  Risk Reduction
   Pollution prevention projects can result in
   reduced noncompliance enforcement actions;
   reduced environmental and worker health
   liability; and reduced risk of on-site contami-
 .  nation via spills, releases, and leaks.

 Potentially, a facility can realize other benefits
 • from the implementation of a comprehensive
 pollution.preventioh program. 'Source reduction
  can lower insurance costs, protect property
values, and improve relationships with financial
institutions. Even though pollution prevention has
clear economic advantages and the techniques can
be simple, inexpensive, and time proven, many.
facilities still do not have significant source
reductionprograms (Haveman, 1995).

This chapter provides information on how to
conduct an assessment of a facility that has a
coating process. It provides information on a
general facility assessment as well as specific
information on assessing the coating process.
Technical assistance providers should be aware  .
that while a facility may have one process or .
chemical that is of major concern, assessing the
entire facility is critical. In this way they can
identify processes that are impacting the coating
process and that might be increasing pollution
generation.   >

Characterizing a

 Facility

Numerous factors can influence whether a facility
adopts and implements pollution prevention
techniques. Understanding what,motivates a  ,.
 facility can help a technical assistance provider
 develop a message for the facility that will influ-
 ence their decision to implement pollution preven-
 tion. The following list divides firms into
"categories and describes some characteristics of.
 firms and their motivating factors:

 > Environmentally proactive firms that
   actively pursue and  invest in strategic
  "environmental management projects:
   Most often these firms are incompliance with
   environmental regulations. They actively
   pursue and invest capital in continuous im-
 '  provement projects that go beyond compli-
   ance in order to maintain their places as
   environmental leaders in their sector. These
   firms are often driven by public recognition,
 '  and pride in industry performance. They
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Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
  understand the economic payoffs of strategic
  environmental investments and believe that
  flexibility in compliance would promote inno-
  vative approaches and increase their willing-
  ness to help other firms.

* Firms that are in compliance but do not
  or cannot seek  opportunities to improve
  environmental performance because they
 .lack the  necessary resources:  Regulatory
  compliance is what drives this potentially large
  middle tier. Barriers to proactive performance
  include a lack of capital and information, and
  a lack of positive  reinforcement.

The barriers that generally apply to some or all of
these facilities are:

* Regulatory compliance and/or enforcement
  actions: Many shops lack the personnel and
  capital resources to move beyond compliance.
  Liability may be a barrier to obtaining loans
  for capital improvements. Existing liability can
  overwhelm their ability to pay for remediation
  or new, cleaner technologies.

*• Development of safer products:  In.some
  cases, suppliers might be reluctant to suggest
  environmentally proactive processes or prod-
  uct changes becpuse these could result in
  lower product sales.

•» Uncertainty about future regulatory activity:
  inconsistency in existing regulatory require-
  ments and enforcement actions at the federal,
  state, and local level creates uncertainty and,
  at worst, competitive imbalances throughout
  the industry. This  climate generates distrust of
  EPA and state programs and can inhibit
  meaningful communication.

* Lack of awareness of changes in product/
  process technology: Facilities .may hot have
  the time or resources to research new tech-
  nologies and the benefits these technologies
  could provide them (Haveman, 1995). In
  some cases, facilities may be aware of the new
  technologies but are unwilling to implement
  them because they cannot field test the new  .
  systems at their facility.
Planning
The key to developing a successful pollution
prevention program is planning. Assistance
providers can work with facilities to implement
planning programs, assist in establishing baseline
measures, and identify potential pollution preven-
tion projects. The key steps to starting a pollution
prevention program include:              -

* Obtaining management support and  involve-
  ment

+ Establishing an in-house pollution prevention
  team

* Attracting company wide involvement

The following pages outline an ideal planning
process. Often, there are issues and limitations
that inhibit a company's ability to carry out all of
the outlined activities. Therefore, this process
should be viewed as a flexible model.

Management Support

The support of company management is essential.
for developing a lasting and successful pollution
prevention program. The level of success that a
facility can achieve in reducing waste generation
appears to depend more on management interest
and commitment than on technical and economic
feasibility, particularly for source reduction
technologies that require process modifications or
housekeeping improvements. In some states, the
technical assistance programs will not work with a
facility until top management has shown that it is
willing to support a long-term pollution prevention
program.

At the outset of the P2 planning program, man- .
 agement endorsement is needed to help identify
the pollution prevention team and give credence to
 the planning effort. Throughout the program,
 company management can support the team by
• endorsing goals and implementation efforts,
 communicating the importance of pollution
 prevention, and encouraging and rewarding  ,
 employee commitment and participation in the
 effort (Dennison, p. 61)".

 At some companies, technical assistance providers
 may find that employees see only the barriers they
                                            16

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                                            Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
 face in implementing a project, which they use as
 excuses to not implement pollution prevention. At
 other firms, motivated'employees are empowered
 to find solutions to overcome obstacles, and the
 compari ies cart reap the benefits of successful
 pollution prevention projects. Technical assistance
 providers should stress to management that a
 successful program has a wide range of benefits.
 These benefits include cost savings, reduced
 liability, and enhanced company image as de-
 scribed earlier.

 Assistance providers should inform management
 that some initial labor costs will be incurred as a
 result of organizing and implementing a pollution
 prevention program'. Usually, however, companies
 find this up-front investment is repaid several
 times over. Case studies often highlight the
 benefits that other companies have realized from
 implementing such programs.

 Technical assistance providers can help facilitate
 management support by developing a plan that
 sells pollution prevention to a company's execu-
 tives. Successful management initiatives that have
 promoted pollution prevention include: developing
 a corporate policy that makes pollution prevention
 a mandate; incorporating pollution prevention
 success into performance evaluations; and offering
 financial incentives for meeting pollution preven- ,
 tion goals or for finding pollution prevention
 opportunities.

  Obviously, each firm is different. The assistance
  provider's approach to each company's leadership
  should attempt to address their specific interests
  and priorities as manifested by the Corporate
  culture. Identifying these interests and priorities is
  a challenge for any assistance team. On these
  visits the teams discuss their priorities and pollu-
  tion prevention in relation to those priorities.
  Technical assistance providers should also stress
  to management that planning is an ongoing task.
  Once the initial plan is completed, the facility
•   should continue to reevaluate their operations to
   identify areas that can be improved (CAMF,
   1995).                               .'•''•

   Establishing the Team

   A successful pollution prevention program re-
   quires not only  support from management, but
CASE STUDY: .
Using Employee Participation to
Reduce Hazardous Waste

The VALSPAR company in Beaumont, Texas,
is a paint manufacturer with 45 employees.
The company produces solvent-based   y
coatings for maintenance and marine use. To
reduce hazardous waste, VALSPAR instituted
a program in which solvent used to clean
mixing,.tanks is recycled back into batch
production. VALSPAR's pollution prevention
program also found innovative ways to elicit
valuable employee participation. The pro-
gram included forming P2 teams composed
of union workers and offering a 2% bonus
for each waste reduction goal attained.

Within the first months of the program, the
 team found a way to recycle 60 gallons of
 additional spent solvent per week, leading to
 a 20% reduction in annual waste generation.
 Eventually, the program was able to recycle
 95% of all solvent used in the clean-up  ,
 process. In addition, VALSPAR accepted and
 reworked unused paint into new batches. In
  1993, the company recycled 52,000 gallons
 of solvent and reworked an additional
 20,000 gallons of returned paint. These
  efforts resulted in a reduction of approxk,
  rndtely 250 tons of hazardous waste at a cos-
  savings of $103,000, not including savings
  from reduced purchases of raw material.
                                '.  (PPIPTI)
also input and participation from all levels of the
organization. To champion the effort, every
pollution prevention program needs an effective
pollution prevention coordinator. Assistance
providers can help identify the team leader, work
with the leader on developing their team, and
suggest ways for the facility to implement its
pollution prevention program.

A team approach allows tasks to be distributed
among several employees and enables staff from
different parts of the company to have input into
the planning process. Members of the team are
typically responsible for:

* Working with upper management to set
  preliminary and long-term goals  ,
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Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
                                          in
+ Gathering and analyzing information relevant
  to the design and implementation of the
  program

* Promoting the program to employees and
  educating them on how they can participate i
  the effort

+ Monitoring and reporting to management on
  the progress of the program (Dennison,Lp. 61)

The pollution prevention team should include
employees who are responsible for planning,
designing, implementing, and maintaining the
program. The ideal size of the team depends on
the size of the organization. In small companies,
the team-can consist of one person who wears
many hats, or the company manager and a
technical person. In larger companies, the team
might includeenvironmental managers, building
supervisors^ technical staff, maintenance staff,
marketing staff, purchasing staff, and other
interested employees (Dennison, p. 63).

External personnel, such as technical assistance
providers or consultants, can complement the
team by providing technical or managerial exper-
tise. Often these people can offer auditing exper-
tise as well as knowledge of pollution prevention,
and environmental laws and regulations. However,
external contributors will be unfamiliar with the
facility's operation. Once the team is established,
assistance providers and regulatory staff should
encourage the facility to take the following steps
to properly evaluate the options for reducing
pollution:

*• Define and Identify the Facility's Objectives:
  Clearly identify, quantify, and rank the facility's
  objectives. For example, at some facilities
  compliance with air quality standards is a
  primary concern while optimized worker
  efficiency and cost are secondary concerns.

* Define Criteria for Evaluating Pollution Preven-
  tion Options: Clearly define what constitutes a
  feasible option. Items to consider in  addition to
  technical feasibility include  economic feasibility,
  quality standards,  and the effect of the option
  on the overall process.

The following pages provide'an overview of the
typical steps involved in assessing a facility and
 coatings processes in particular. These steps
 include:            .

 * Characterizing the facility
 + Gathering baseline facility data •
 * Analyzing work-place practices
 * Developing process flow diagrams
 + Identifying pollution prevention options
 > Analyzing and selecting options for further
   investigation
 * Pilot testing preferred options      ,
 * Implementing the new system
 * Evaluating and maintaining the pollution
   prevention program

 While the facility may have brought in a technical
 assistance provider to suggest methods for a single
 process or problem, the entire facility must be
 evaluated because the coating process will be
 affected by outside issues. Consider the case of a
 facility that wants to change from solvent cleaning
 to aqueous cleaning but has problems with
 removing cutting fluids. The machining process
 would need to be examined to see if the facility
 could use alternative cutting fluids that are easily
 removed using aqueous cleaning.

 Assess the  Facility

 Once the team has defined its objectives and
 criteria for a pollution prevention program, the
 next step is to assess the facility. Beyond the
 facility tour, useful information for the assessment
 can be obtained from sources such as:

 * Engineering interviews and records
 +Accounting interviews and records
 * Manifest documents
 •* Vendor data
 * Regulatory documents
 * Sampling data

 Map the  Facility

 Locate or prepare drawings of the layout of the
 process and storage areas. These drawings should
 be to scale, showing the location of all relevant
 equipment and tanks, and identifying:

 * Floor space of the facility
" * Coating and other process lines
 * Gutters, sumps, and sewer lines .
 * Water lines, control valves, and flow regulators
 * Ventilation/exhaust systems
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                                            Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
 Gather  Baseline Information

 The first step in P2 assessments of coatings
 processes is to collect as much information as   .,.
 possible about the coating process from company
 personnel. Background information should
 establish the sources and nature of wastes gener-
 ated, and can include:

 * Specific information about emissions (e.g.,
  current releases, desire'd reductions) and other
  wastes generated from coatings operations
  (e.g., wastewaters and paint wastes)

 * Details about the type of coating used and
 • application techniques

 * Information about the types of parts to be
  coated and performance specifications of the
  finish  •--..-.

 * Details about the surface preparatiorTand
  equipment cleaning processes (e.g., equip-
•  ment and methods used) ;    •

 Technical assistance providers should also review
 all operations of the facility that relate to chemical,
 energy, or water use. Some of the information that
 technical assistance providers'should request
 includes:.                     .          /

 * Estimates of production units, such as square
   me'ters coated and number of parts that pass
   through a line sequence, or production.rates
   (i.e., square feet processed per hour)
 * Material purchases
 * Material inventory    ..
 * Material use rates (where each material is
   used and how much is used in each process)
 * Waste management costs
 * Raw material costs  •        '    • '  ,
 * Compliance problems
 *• Control processes
 * .Sampling and analysis information
 * Process line design and condition
 ^Actual operating procedures
 * Operating parameters             .       •

 The information listed above should be used in
 conjunction with the information obtained in the
 walk-through of the facility to determine what
 pollution prevention options are technically and
 economically feasible. This information should
 also provide the technical assistance provider with
 information to determine which processes in a
 facility need to be addressed to reduce pollution
 generation.

 Analyze Workplace  Practices

 A great deal of data should be accumulated so that
 assistance providers can determine the best
 pollution prevention approaches for a facility. The
 first pieces of information gathered should be
 material/resource use, general operating proce-
 dures, and facility information. This information
 usually can be gathered prior to a facility tour and
 used to start a facility map that will be valuable
' during the site visit. Table 5 provides an overview
 of the basic operational information that technical
 assistance providers should obtain from the
 company prior to the technical assistance visit.

 Additional information is gathered during the
 facility tour. When touring the coatings operations
 at a facility, technical assistance providers should
 observe or ask employees about workplace
 operating practices. Often, employees can provide
 valuable insight both into why waste is being"
 generated and into some of the obstacles a plant
 may face in implementing new projects or meth-
 ods. The following lists present some of the
 questions technical assistance providers might
 wanttoask(KSBEAP,p.33):                s

 Personnel
 4 Do employees view overs'pray as lost product?
 * Are paint and solvent records maintained for
   each spray gun operator?
 > Are gun operators or paint crews rewarded for
   high quality work using less paint?
 + Are there written guidelines' on how much paint
   should be prepared and used'for frequent
   jobs?
 * Are employees provided with proper devices
   to measure the correct anrfount of paint? .
 . *• Are operators given spray gun training?
 * Is technique training routinely provided?  r
 + Are performance  monitors in place?'

 Housekeeping/Maintenance
 * Is spray equipment maintained according to
   manufacturer or vendor instructions? -
 * Are paint containers tightly closed when not in
   use?       . :              .         •   • •
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Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
 Table 5.  Overview of Assessment Information (BCDNRP)
 Process
Data
 Production  Processes
 and Operational Procedures
* Production rates
+ Process description and efficiencies
* Condition of process equipment
*• Sources or potential sources of leaks/spills
* Operating procedures
* Maintenance procedures and schedules
+ Energy/utility use and costs
* Operating and maintenance costs
 Material Use, Handling,
 and Storage
  Paint and solvent use        •
  Raw material accounting (how much of the materialis
  is used in the process, how much is lost through evapo-
  ration or other means, and how much enters the waste
  stream)   '            .                     .
  Raw material costs
  Material transfer and handling  procedures
  Storage procedures         '
  Sources of leaks or spills in transfer and storage areas
  Waste Stream
+ Activities, processes, or input materials that generate
  waste streams             '
* Physical and chemical characteristics of each stream
* Hazardous classification of each waste stream
* Rates of generation of each waste stream and variability
  in these rates
 Waste Management
  Current treatment and disposal system for each waste
  stream
  Cost of managing waste stream (e.g., fees, labor, and
  disposal costs)                         .
  Efficiency of waste treatment units
  Quantity and characteristics of all treated wastes
  Waste stream mixing (hazardous wastes mixed with non-
  hazardous waste) •
 Waste Reduction
   Current waste reduction and recycling methods being
   implemented
   Effectiveness of those methods
 *• Are there regular inspections and repairs for    Inventory Control
   paint and solvent leaks?
 4,Are tight-fitting spigots used?
 * Are spigots orpumps used to transfer paint
   from storage containers to smaller containers?
          *'Are good records kept on paint inventory.and
            use?
          * Are paint purchase expenses allocated to the
            painting department?                  .
          * Are paint containers adequately labeled?
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                                            Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
* Are paints stored on the floor according to
-  manufacturer's instructions?      :
+ Are paints used on a first-in, first-out basis?
•* Is access to the paint room controlled?
«• Is access to solvents controlled?
•» Are unused or expired paints returned to     .
  vendors or manufacturers?
^ Is a computerized paint-mixing system used?

Scheduling
* Are certain production runs scheduled around
  the same time each month?                 -  .
* Are jobs scheduled  so that jobs using the same
  color are scheduled together?
•* Are production runs scheduled to go from
  lighter to darker colors?

Equipment and  Materials
+.Are efficient spray guns being used (e.g., HVLR
  electrostatic)?            ;      '          ,
* Are paints maintained at proper viscosity?
«• Is'the correct gun setup being used for the
  paint and the workpiece?
 * Is it possible to reduce gun pressure and
  achieve an acceptable finish?
 * Are gun operators keeping the spray pattern
  over the workpiece?
 + Are gun operators holding the gun perpen-
•  dicular to the work surface?
 * When part size allows, are operators making a
   pass over the full length of the work surface?
 * Are paints with less or no hazardous ingredi-
   ents being used?
 *Are high-solids or powder coatings used?

 Rework
 •* Is touch up dpne.only on the imperfection or
  : reworks?
 + If paint is stripped, are mechanical methods
   being used instead of chemical ones?
 * If using chemical stripping, are less toxic
   strippers being  used?

 Cleanup and Disposal
 *• Are waste paint handling and solvent handling
   charges allocated to the production units or
   departments that incur them?
  * Are guns, nozzles, and lines cleaned irfimedi-
 •  ately-after use?                  •
  * Are enclosed paint gun cleaners used?
  •* Is compressed air used to clean lines instead
  of sol vent?   ,
* Are spatulas or scrapers used to clean equip-
  ment and paint containers prior to using
  solvents?         ,
* Are polystyrene filters used?
* Is unused paint stored properly so that it can
  be .used again?      ,
* If waste paint cannot be used onsite, are there
  potential employee or local uses?
+ Is solvent recycled onsite?
* Is solvent gravity separated from waste
  sludge?             ,

If the technical assistance provider uses the team.
approach described above, many individuals from
all areas of the company will have a chance to
share their perspective on pollution problems and
solutions. Working with this information, technical
assistance providers can develop a process map,
including data information. Using these tools, the
P2 team can go onto the plant floor to discuss the
process with those directly involved (e.g., supervi-
sors and front-line production workers) to deter-
mine appropriate P2 projects and develop a
baseline to measure all future efforts.

 Develop  a Process  Flow  Diagram

 Once all the information has been gathered and a
 map of the facility is drawn, technical assistance
 providers can develop a process-flow diagram.
 Process-flow diagrams break the facility down
 into functional units, each of which can be
 portrayed in terms of material inputs, outputs, and
 losses. Developing a process map helps the facility
 understand how the production process is orga-
 nized, thereby providing a focal point for identify-
 ing and prioritizing sources of emissions'and waste
 (EPAp, 1996).
     t                      •
 The process map should cover the main opera-'
 tions of the facility and any ancillary operations
 (e.g., shipping and receiving, chemical mixing
 areas, and maintenance operations). Separate
 maps can be generated for these ancillary opera-
 tions. Another important area to cover is "inter-
 mittent operations" or operations that do not occur
 on a regular basis. The most common intermittent
 operations are cleaning and maintenance. A great
  many pollution prevention opportunities can be
  found by examining these interm ittent operations
  (EPAp, 1996).
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Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
Assistance providers should also help the facility
to include operations that are upstream and
downstream of the coating operation. For ex-
ample, machining operations could have a major
impact on cleaning operations. Pollution and waste
issues often cross process boundaries. An under-
standing of the origins of the pollution can assist
the facility in identifying opportunities for pollution
prevention.

Identify  Pollution

Prevention

Opportunities

Using the information obtained in the facility
assessment, the team should compile a list of P2
options that are technically feasible. Brainstorming
sessions with the P2 team can provide innovative
ideas. Researching case studies of other compa-
nies also can provide valuable information. Other
potential sources of ideas include suppliers and
consultants. At this point, all ideas should betaken
seriously, and none should be-rejected automati-
cally for reasons such as "that's already been
tried," or "it will never work," or "it's too expen-
sive."

• After all options have been identified, the team
should screen the options based on the objectives
and criteria that were established in the assess-
ment phase. Each option'should fit into one of the
following categories:

 + Ideas that are impractical   .
 * Ideas that need more detailed information and
   study
 + Ideas that can be implemented with a mini-
   mum of effort and cost

 This initial evaluation will assist the company in   .
 identifying a subset of options that deserve further
 investigation. Generally, the number of options
 requiring detailed information and study should be
 pared to a minimum (Ferrari, 1994).

 When screening ideas, assistance providers should
 keep in mind that an important principle of
 excellence in manufacturing is maximizing the
 productivity of the coating process. Some pollu-
 tion prevention options can increase productivity
 while others can decrease productivity, sometimes
 substantially. Technical assistance providers
should be aware of how their suggestions can
affect the productivity of the coatings process
when screening options. By gaining information
on these types of issues, technical assistance
providers can provide better suggestions on
pollution prevention options when assessing a .
facility.

Analyze and  Select

Options

Once a short list of options has been identified,
the team should begin the process of deciding
which options are appropriate for the facility.
During this phase, the team should be clear on the
company's objectives and criteria. Depending on
the goals of the company, cost effectiveness might
not be the overriding goal. The following ques-
tions should be asked when screening options:

* Which options will best achieve the companies
  waste/emissidns reduction goals?
> What are the main benefits to be gained by
  implementing this option?
* Does the technology exist to implement the
  option?
* How much does it cost?
* Can the option be implemented without major
  disruptions in production?
* Does the option have a good track record?
* Does the option require additional space?
* What are other areas that might be affected by
   implementation of the option?

In addition, a company thatbelieves cost effec-
tiveness is critical should consider the long-term
costs associated with a particular option. For
 instance, the team might be inclined to disregard
an option because'the initial capital outlay is high;
 however, upon examining the total cost associated
 with the project, the team might find that the
 measure could yield impressive savings in several
 years (Dennison, p. 75). In order to identify the
 total costs associated with both existing and new
 processes, the facility could consider costs that
 traditionally have not been incorporated into
 capital acquisitions. For more information on
 identifying these costs, assistance providers can
 refer to Improving Your Competitive Position:
 Strategic and Financial Assessment of Pollution
 Prevention Projects, a training manual developed
 by NEWMOA for conducting financial assess-
 ments of pollution prevention projects.
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                                         Chapter 3: Planning Pollution Prevention Programs at Coating Facilities
 Pilot Test  or Validate
 Preferred Options

 Once the facility has determined -its preferred
 option(s), the facility can pilot test the program
 prior to full facility implementation. A pilot test
 c?.n highlight any installation or implementation
 issues. At this point, the technical assistance
 provider has completed most of his or her job.
 However, if issues arise in the pilot test phase, he
 or she can be called in to troubleshoot and suggest
 other alternatives. The technical assistance
 provider could brief the facility's P2 team on how
 to anticipate and prevent problems and issues
 during implementation of the new system. This
 could be useful because the cost to correct a failed
 system can greatly exceed the cost of proper initial
 implementation."                      .

 Procure and

 Implement  New
 System

 Once the new system is installed, the company's
 employees should be informed about the project.
 arid the importance of their cooperation and
 involvement. Operators should be trained on how
 to properly operate the system. Companies should
 update employees on the expected benefits of and
 the progress rriade in achieving the goals of the
 new system.                         '

 Frequent updates on the progress of the overall P2
 program can increase a staff s stake in the pro-
 • gram. In orderto sustain ernployee interest in P2,
 facilities should encourage staff to submit new
• ideas for increasing the effectiveness of the
 ' program.                     '     -

 A few critical rules should be kept in mind when
 helping a company consider new projects:  '

 > No single system or process is right'for all
   .applications. A vast range of variables can
    affect the coatings process which, in turn,
    affects the selection and performance of a    :
 .  • pollution prevention system..Specific variables
    include work type, work loading rate,
    workpiece geometry, substrate materials/ and
    finish requirements.                .      .
            f
+ Prior to investing m any new system, the team
 , should take the time to evaluate and under- •
  stand the process, preferably including a
  rigorous pilot test in the facility.

«• The team, should, recognize that the provider of
  any new system (including the designer and.
  sales staff) is a new partner at .the facility
  (Ferrari, 1994).              '

Evaluate and Keep

the Program Going:

Assistance providers can suggest that the facility
develop a mechanism for soliciting input from all
employees in the future. Communicating the
success of the program also can keep employees
involved. The facility can use the baseline infor-
mation developed from the facility assessment
phase to communicate any progress that has been
made. Technical assistance programs can follow
up with a facility (usually within 6 months to one
year from their final visit) to report on the suc-
cesses and failures of the company's P2 program
 and leam of new projects that the facility may
 have implemented.
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   Overview  of  Pollution
   Prevention  in   Coating
   Application  Processes
Q ignificaht amounts of pollutants are generated
O from paint and coatings processes. The exact
amount for the nation is difficult to calculate,
because use is spread across numerous industry
groups (EPA, p. 158), and companies do not
report-emissions by manufacturing process to
EPA. Wastes from paint application include
leftover paints, dirty thinner from the cleaning of
spray guns and paint cups, air emissions of VOCs
and HAPs, dirty spray booth filters, dirty rags,
debris from area wash downs, and outdated
supplies. Simple and cost-effective ways to reduce
these wastes include rigid inventory control, good
housekeeping practices, proper paint mixing,
increased operator training, high transfer effi-
ciency equipment, proper cleaning methods,
alternative coatings, reusable paint booth filters,
recycling solvents, and the use of waste exchanges
(KSBEAP, p. 21). This chapter presents an
overview of these techniques while detailed
information on specific technologies are covered
in subsequent chapters: Table 7 presents a broad
overview of pollution prevention opportunities in
coating operations.

Rigid  Inventory  Control

Rigid inventory control is an efficient and effective
way of reducing indiscriminate use of raw materi-
als. The facility should monitor employee opera-
tions and make verbal or written comments on
product use. Another option is to limit employee
access to storage areas containing raw materials.
This inaccessibility can force employees to stretch
the use of raw materials (EPAr, p.8). Rigid control
 can reduce solvent use by as much as 50%.

 Good  Housekeeping

 Improvements in better operating practices, or
. "good housekeeping" methods apply to all emis-
 sions and waste streams, require minimal capital
 outlays, and can be very effective in reducing
wastes and pollutants. Good housekeeping
includes the development of management initia-
tives to increase employee awareness of the need
for, and benefits of: pollution preventipn; preven-
tative maintenance to reduce the number of leaks
and spills; and efficient use of raw materials.  .
Table 6 presents a summary of good housekeep-
ing measures that are described in detail in this
chapter.

Many methods are available to control and
minimize material losses. The following ap-
proaches to bulk material drum consolidation,
material transfer methods, evaporation, and drum
transport can effectively limit material loss:

* Control inventory by storing drums together in .
  an area of limited accessibility
* Reduce leaks and spills by placing drums at
  points  of highest use
* Use spigots or pumps to transfer materials
  from storage containers to "working" contain-
  ers            ,              .      .
> Control evaporation by using tight-fitting lids
  and spigots                    •
+ Use drip pans
• Use secondary containment in bulk storage
  areas
* Move  drums correctly to prevent damage or
  punctures that could lead to leaks or ruptures
•  during future use (EPAr, p.8).    "            '

 Paint  Mixing

 In many cases, facilities will mix a fixed amount of
 paint for each job (e,g., one pint'or one quart).   .
 For small jobs especially, the amount of paint
 prepared often exceeds the amount of paint
 actually applied. Facilities can encourage the use
 of the correct amount of paint by having various
 size&bf paint-mixing and sprayer cups available to
 limit overmixing. Any paint not used for a job is
                                        25

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Chapter 4; Overview of Pollution Prevention in Coating Application Processes


       Table 6. Opportunities for Improved Housekeeping in Coating Operations
                 (KSBEAP, p. 21)
       Waste
Method
       General
* Improve material handling and storage to avoid spills
* Segregate waste streams
* Perform preventative maintenance          .
* Practice emergency preparedness
* Charge departments generating waste for costs associated with man-
  agement and disposal                           '
       Paint Waste
* Maintain rigid inventory control to reduce thinner use
* Initiate routine'mainfenance and training to reduce leaks and spills
*Mix paint according to need; document use
* Provide operator training to improve transfer efficiency
* Schedule jobs to maximize color runs
       Solvent Waste
* Control inventory to reduce use
^Substitute coating material for one with low or no solvents
^Substitute cleaning solution for one with low or no solvents
+ Practice proper equipment cleaning methods
* Recycle solvents onsite
       usually considered a hazardous waste and should
       be disposed of as such. A disadvantage to this
       technique is that if too little paint is mixed for the
       job and more needs to be made, color matching
       can be difficult (EPAr, p. 9).

       Operator Training

       Operators may be skilled in producing high quality
       finishes but poorly trained in minimizing paint use.
       Technical assistance providers can help operators
       by teaching them to:           "
       * Avoid arcing the spray gun and blowing
         paint into the air
       + Maintain a fixed distance from the painted
         surface while triggering the gun
       *• Keep air pressure (which is often set too high)
         low; this can increase transfer efficiency by 30
         to 60%
       + Keep the gun  perpendicular to  the surface
         being painted  '
       * Use proper on/off trigger technique (KSBEAP,
         p.23)
                      High  Transfer  Efficiency
                      Equipment
                      Less overspray means reduced emissions. Trans-
                      fer efficiency is a measure of how much paint
                      actually goes on the product, compared to how
                      much paint is sprayed. Typical transfer efficiency
                      from conventional guns ranges from 20 to 40%,
                      making average overspray rates 60 to 80%. For
                      more information on high transfer efficiency
                      equipment, refer to chapter 7.

                      Alternative  Coatings
                      Painting usually consists of applying a primer/
                      surfacer followed by one or more coats of paint.
                      VOC emissions are directly related to the types of
                      paints used. Technical assistance programs should
                      assist companies in identifying any potential
                      alternative coatings such as powder, waterborne,
                      or high-solids coatings'. For more information on
                      alternative coatings, refer to chapter 6.

                      Proper Cleaning Methods

                      Reducing solvent use in equipment cleaning can
                      significantly reduce pollution. This can include:
                                                  26

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                                              Chapter 4: Overview of Pollution Prevention in Coating, Application Processes
> Scraping paint cups or tanks before rinsing
  with solvent
 «• Making use of Teflon-lined metal paint con-
•' tainers that are easier to clean
> Using an "enclosed gun-cleaning station  .
 * Spraying solvent through the gun into the •
  cleaning station where it is condensed for
  recovery and reuse
 * Scheduling jobs^so that large batches of
  similar items are painted instead of scheduling
  jobs so that small batches of custom items are
  painted. This reduces the amount of solvent
                     and waste paint generated
                   * Scheduling jobs from light.to dark colors to
                    , minimize cleaning between colors (EPA, p..10)
                   For more information on proper equipment cleaning
                   methods, refer to chapter 8.

                   Filters

                   .Reducing the amount of filters used in painting can
                   reduce hazardous waste generation. Facilities
                   should handle filters as a hazardous waste if they
                   contain wet paint (e.g., solvents), due to their
  Table 7.  P2 Options for Coatings Processes (KSBEAP, p. 23 and IHWRIC, p.
             39-40)
  P2 Options
Description
                                      Benefits
  Use Low-VOC Paint
> Substitute waterborne, powder,
 UV curable or high-solids paints
 fqr solvent-borne paint
> Use paints that have less toxic pigments
                                       + Reduces VOC emissions
                                       * Reduces toxicity of paint
                                       .  sludge
  Increase Transfer
  Efficiency
  Use electrostatic spraying
  Use flow coating, roller coating, or
  : electrodeposition
  Improve operating practices
  • Provide operator training
                                      * Reduces pointless
                                        due to oversprgy
   Reduce Quantity and
   Toxicity of Solutions
   Used for Surface
   Preparation
  Reduce solvent evaporation by
  installing tank lids,-increasing
  freeboard space, and installing     ,
  freeboard chillers in conventional
  solvent vapor degreasing unfts
  Use aqueous solutions or mechanical
  methods
  Maximize mechanical or aqueous
  cleaning processes
                                      * Reduces spent solvents,
                                        aqueous solutions and.
                                        rinsewqter from surface
                                        preparation
                                      * Reduces VOG emissions
   Reduce; Equipment
   Cleaning Waste
• > Use less toxic solvents
*• Install gun washer
+ Adopt distillation/recycling practices
+ Use enclosed cleaning devices
                                       * Reduces VOC emissions
                                       * Reduces toxicity of
                                        'cleaning wastes.
   Adopt Better
   Housekeeping
   Practices
 * Segregate waste stream's
 * Implement rigid inventory control
 + Improve material handling and storage
 * Mix paint according to need;
 ,  document use
 * Schedule jobs to maximize color runs
 * Perform preventative maintenance
 ».Practice 'emergency preparedness
                                       * Reduces paint waste '
                                       >Reduces solvent use   -
                                       * Reduces'leaks and spills
                                             27

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Chapter 4: Overview of Pollution Prevention in Coating Application Processes


       flammability and the existence of toxics in the
       paint. One method for reducing filter waste is to
       use a cleanable polystyrene filter or a reusable
       metal filter. When the filter is too clogged for use,
       it can be cleaned by blowing compressed air over
       the filter until it is clean.enough for reuse (paint ,
       removed in this process would require collection
       and may still be classified as a hazardous waste)
       (EPAr,p. 13).

       On-site  Solvent  Recycling

        Several alternatives are available for recycling
        solvents onsite. Gravity separation is inexpensive
        and relatively easy to implement. This technique
        enables a solvent/sludge mixture to separate under
        quiescent conditions. The clear solvent can be
        decanted with a drum pump and used for equip-
        ment cleaning. This reduces the amount of wash
        solvent purchased. Reclaimed solvent also can be
        used for formulating primers and base coats, but
        might create problems if it is not sufficiently pure.

        For those facilities that generate large quantities of
        waste solvent, on-site distillation may provide a
        more cost-effective solution. Batch distillation of
        all high-grade solvent wastes can virtually elimi-
        nate the need to purchase lower-quality solvents
        used in priming and cleaning operations. An
        operator can reclaim 4.5 gallons of thinner, with
        0.5 gallons left as sludge. This ratio will vary
        depending on the specific operation (EPAf, p. 11).
        For more information on solvent distillation, refer
        to chapter 5.

        Waste exchanges provide another alternative for
        reducing waste disposal costs. Waste exchanges
        are organizations that manage or arrange for the
        transfer of wastes between companies, where one
         producer's waste becomes another producer's
         feedstock. Most exchanges exist as information
         clearinghouses that provide information on
      •   available wastes. Opportunities exist for these
         exchanges to oversee direct transfer (without
         processing) of waste solvents from one company
         toanother(KSBEAP,p.24).             '   .
                                                      28

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    Surface  Preparation
   This chapter covers a variety of surface prepa-
   ration methods along with technology-specific
suggestions for optimizing processes in order to
reduce waste. Detailed descriptions of techniques
for optimizing traditional cleaning methods and
alternative cleaning methods, eliminating pollutants
from conversion coatings, and modifying or
replacing traditional stripping operations are
provided below. For an overview of alternative
surface preparation technologies, refer to table 8.

General Description

Methods for surface preparation vary depending
on the material to be painted, the paint to be used
and the desired properties of the resulting finish  .
(IHWRIC, p. 33). Many products require a
preparation step prior to painting. This step is
commonly called pretreatment for new products,
or paint stripping for products that need to be
reworked (Ohio EPA, p. 1). Pretreatment of a
metal surface can include chemical-assisted
cleaning, mechanical cleaning, and chemical or
abrasive blasting, application of conversion
coatings or stripping methods.
     P2 Tips for Surface Preparation

  * Improve current .operating practices
  > Set standards for cleaning and stripping
  * Use aqueous cleaners and/or mechanical -
    methods when possible
  * Maximize the cleaning capacity of current
    methods                    •
 Halogenated solvents have traditionally been used
 as cleaning and stripping agents. Conventional
 surface preparation generally involves applying
 some form of a solvent. However, environmental
 problems with air emissions often arise from
 solvent use. In addition, after surface preparation,
 a waste stream composed of the solvent combined
 with oil, debris and other contaminants is left for
 disposal (EPAij p. 1). Fortunately, a number of
 alternative methods are now widely available.
These are discussed in the cleaning section of this
chapter. Surface preparation can consist of a
variety of processes including several cleaning  .
steps, conversion coatings, and a stripping opera-
tion.

Pollution Problem

Surface preparation can generate a number of
wastes, including spent abrasives, solvents and/or
aqueous cleaning baths, and surface treatment
baths; air emissions from abrasives and solvents;
rinsewaters following aqueous processing steps;
and solvent-soaked rags used for wiping parts
before painting. Depending on the complexity of
the operation and the nature of the chemicals
used, the volume and toxichy of wastes generated
can vary widely (Freeman, p. 484-485).

Removing old paints that contain lead, for ex-
ample, can be particularly problematic, as abrasive
stripping of these paints generates a fine lead dust
that is highly toxic to workers. The use of sand
and other silica-containing materials in stripping
processes also has been associated with lung
disease in workers (IHWRIC, p. 48).

Mechanical Cleaning

 Usually, the first step in the surface preparation
 process is to mechanically remove rust or debris
 from the substrate. Wiping loose dust and dirt off
 the part is an example of mechanical cleaning.
 Typically, though, more aggressive mechanical
 action is needed to remove rust or other contamii-
 nates. Rust and metal scale can be removed
 mechanically by sanding, brushing with a wire
 brush or plastic "wool" pads, or by using abrasive
 blasting techniques (KSBEAP, p. 1-2). Abrasive
 blasting can also be used for removing old paint
 from products; solvent-based chemical stripping is
 another option. Environmental concerns and rising
 chemical prices have pushed more companies into
 using mechanical cleaning to accomplish a larger
 portion of the cleaning process (KSBEAP, p. 1).
                                           29

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Chapter 5: Surface Preparation
Chemically-Assisted

Cleaning

Traditionally, solvents have been used for remov-
ing contaminates such as oils and greases. Compa-
nies use various solvent-based methods to clean a
workpiece. For example, metal parts can be
immersed in a solvent tank (i.e., cold cleaning).
Solvents also can be wiped or sprayed onto the
parts, or solvent vapor degreasing units can be
used. There are environmental problems associ-
ated with all of these cleaning methods.,Dip tanks
get dirty as they are'used. Spraying can be
wasteful if too much solvent is used. Wiping is
labor intensive. Vapor degreasers are regulated
under the Clean Air Act and OSHA and pose
health hazards. Often a combination of techniques
can be used to reduce solvent use and still obtain a
properly cleaned workpiece. For example, a dip
tank can be used followed by wiping or confined
.spraying. The key to solvent cleaning is to have
the part as clean as possible before it enters the
solvent cleaning process (KSBEAP, p.2). Optimiz-
ing solvent cleaning systems and alternatives to
solvent cleaning are discussed in greater detail in
the cleaning section of this chapter.

Conversion  Coatings

A conversion coating may be applied to the
workpiece prior to painting to improve adhesion,
corrosion resistance, and thermal capability.
Conversion coatings chemically react with the
metal surface to create a physical surface that
allows for better paint adhesion. In addition,
conversion coatings act as a buffer between the
coaling and the substrate, reducing the effects of
sudden temperature changes. Phosphate and
aluminum conversion coatings are usually con-
fined to large operations with elaborate waste
treatment facilities because of the extensive
regulations controlling the disposal of rinse waters
and sludges containing heavy metals. For more
 information on conversion coatings, refer to the
 section on conversion coatings in this chapter.

 Stripping

 When a part needs repainting, the old paint usually
 must be removed "before a new coating can be
 applied. The first thing a technical assistance
• provider should do is determine why the piece
needs to be reworked. Reducing reject rates can
greatly reduce the amount of waste generated
from these processes. Once the need for rework
,has been reduced, alternative stripping methods
can be examined.

General  P2  Options

for Surface

 Preparation

This section covers general methods to improve
the efficiency of the surface preparation process
and to reduce the pollution generated during the
surface preparation processes. Detailed informa-
tion on alternative technologies/processes is
discussed.     ,               .           '

A cost-effective method for reducing these wastes
 is to minimize the need for surface preparation by
(1) improving current operating practices and (2)
 setting standards for cleaning and stripping. If the
 need for surface preparation cannot be reduced by
these methods, alternative technologies must be
 assessed (MnTAP, p. 1). Maximizing the cleaning
 capacity of current methods also can help reduce
 wastesr(KSBEAP, p. 2). Each of these options is
 discussed below.

 Improve  Current  Operating
 Practices

 To reduce the need for cleaning, technical assis-
 tance providers can help companies examine the
 sources of workpiece contamination. Technical
 assistance providers should determine how
 contaminants such as lubricants from machining,
 dirt from the manufacturing environment, and
 finger oil from handling by shop personnel are
 contaminating the workpieces. Once the contami-
 nation sources are identified, technical assistance
 providers can help determine whether some or all
 contamination sources can be eliminated by
 improving current operating practices. For ex-  •
 ample, proper storage of materials and just-irj-time
 delivery of parts can keep contaminants from
 becoming a problem (KSBEAP, p. 1): To elimi-
 nate finger oil contamination, gloves can be used
 in areas of parts handling; gloves can be made of
 lint-free material, or lint can be removed with a
 dry cloth (OH EPAe, p. 1).
                                           30

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                                                                       Chapter 5: Surface Preparation
 In the case of paint stripping, technical assistance
 providers can help firms examine what causes the
 need for paint stripping. Possibilities include:
 inadequate initial part preparation, defects in
 coating application, improper time/temperature
 cycle for the curing oven, and equipment prob-
 lems or coating damage due to improper handling.,
 While no process is perfect, reducing the need for
 repainting can greatly reduce the volume of waste
 generated from paint removal (MnTAP, p. 1 -2).

 Set Standards for Cleaning and
 Stripping

. Next, companies should determine the cleanliness
 level or cleanliness standard that is needed.
 Gleaning requirements are generally based on two
 factors: process specifications and customer
 requirements. A system to measure cleanliness
 should be used to prevent over-cleaning arid
 ensure efficient use of cleaning agents
 (MnTAPe).'    .

 In the case of abrasive stripping, standards should
 be set to avoid blasting a surface longer than
 necessary, creating excess waste and reducing
 productivity. Measuring devices can be used to
 define the level of surface scratching or "profile"
 . desired. Most standards use Structural Steel
 Painting Council (SSPC) classifications for surface
 cleanliness. There are two types pf standards
 . available: visual disk and photographic. A surface
 profiler instrument also can be used (Freeman, p.
 490-491).                             '   .

 . Pollution prevention approaches tends to favor
  mechanical or aqueous cleaning methods, but
  solvent vapor degreasing can be more economical
  and suitable for certain types of parts (e.g., parts
  that slide into each other to form a close fit,
  preventing  some surfaces from being exposed)
  (MnTAP, p. 2). Advanced technologies have
  made both of these processes more effective and
  less harmful to the environment (Freeman, p.
  469.). More information on this topic is found in
  the cleaning section of this chapter.
Maximize  Cleaning  Capacity  of
Current  Methods2

The following practices should be implemented
where possible to maximize the cleaning capacity
of aqueous or solvent cleaners:

+ Use countercurrent cleaning (i.e., begin with
  "dirty" cleaner, followed by "clean" cleaner)
* Add an additional rinse
* Recycle cleaning solvent and rinsewater
* For aqueous cleaners, control water tempera-
  ture and pressure. For example, elevated
  temperature solutions are more effective for
  removing greases and oils (KSBEAP, p: 2)

The following sections provide more detail on
specific surface preparation processes including
solvent vapor degreasing, aqueous cleaning,
alternative solvents, phosphatizing, anodizing,
stripping, and abrasive blasting.
 Cleaning
 This section provides information on a variety of
 conventional and alternative P2 technologies
 typically used for cleaning and degreasing metal
 parts prior to coating.

 Solvent  Vapor Degreasing

 The conventional method used for cleaning most
 metal parts is vapor degreasing using a variety of
 halogenated solvents. In vapdr degreasing, parts
 are usually suspended over a solvent tank. The
 solvents are then heated to their boiling point,
 which creates a vapor that condenses on the parts
 and dissolves contaminants. The condensate drips
 back into the tank along with the contain inants.
 However, because the contaminants usually have
 higher boiling points than the solvent, the vapor
 itself remains  relatively pure. The cleaning process
 is complete when the parts reach the temperature
 of the vapor, and no more condensate is generated
 (EPAh,p.2).

 Advantages and Disadvantages

 Unlike other cleaning processes involving water,
 solvent vapor degreasing does not require  down-
  '  For m6re information on setting cleanliness standards, see Is it Clean? Testing for Cleanliness of Metal Surfaces by
  Anselm Kuhn in the September 1993 issue of Metal Finishing.'          '

  2 For.more information on extending the life of aqueous cleaning solutions, see Extending fhet/fe of Aqueous Cleaning
  Solutions a fact sheet developed by the Office of Pollution Prevention, Ohio Environmental Protection Agency.
                                               31

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Chapter 5: Surface Preparation
  CASE STUDY:
  Crown Equipment Corporation

  Crown Equipment Corporation of New
  Bremen, Ohio, is a manufacturer of electric
  lift trucks and antenna rotators. Between 1987
  and 1991, Crown removed methyl ethyl
  ketone (MEK), methyl chloride, toluene and
  1', 1,1 -trichloroethane from its cleaning and
  degreasing operations by changing over to
  aqueous cleaning.

  In painting operations, Crown has removed
  lead and chromium from most paint formula-
  tions, eliminating hazardous paint waste. Paint
  sludge is recycled into building materials such
  as quarry tile, asphalt, mastic, and binder.

  Savings
  Changing over to aqueous cleaning initially
  cost Crown $78,000, but the company now
  saves m ore tha n $ 103,000 per yea r
  (OH EPAc).
 stream drying because the solvent vaporizes from
 the parts over time. However, solvents such as
 •TCE vaporize resulting in significant VOC emis-
 sions and solvent losses (Freeman, p. 468). Other
 common solvents are either toxic, HAPs, and/or
 o.zone depleters. In fact, conventional vapor
 degreasing units commonly lose 60% of their
 solvents through evaporation (SHWEC, p. 1).

 Solvent Vapor Degreasing Processes

 Conventional vapor degreasing units or open-top
 vapor cleaners (OTVC) use an open tank where a
 layer of solvent vapor is maintained. Air emissions
 from an OTVC occur during startup, shutdown,
 working, idling, and downtime. However, move-
 ment of the work load in and out of the vapor
 degreaser is the main cause of air emissions (EPAi,
 p. 7). During startup, losses occur as the solvent in
 the sump is heated and a vapor layer is established
 in the open tank. Shutdown losses occur when the
 unit is switched off and this vapor layer subsides.
 Downtime losses occur due to normal evaporation
 of the solvent when the OTVCis not in use. Idling
 losses occur by diffusion from the vapor layer in
 the period between loads. Completely enclosed
 vapor cleaners (CEVC) are available, although use
is generally confined to Europe (Freeman, p. 468-
474).

Process Optimization

A number of equipment-related and operational
changes can reduce solvent emissions from
traditional OTVCs by as much as 50%. Many of
these practices are required under the MACT
standard since solvent degreasers are regulated
under the NESHAP. These include:

+ Minimizing solvent drag-out by improving  •
  parts drainage over the tank
* Superheating vapors
+ Minimizing convective losses by lowering and
  raising parts with a hoist at a speed less than
  11 feet per minute
«• Rotating complex parts
* Building a degreaser enclosure
* Placing, a cover on the OTVC opening during
  idling and shutdown
* Minimizing air movement over the degreaser

Degreasing with  Liquid  Solvents
(Cold   Cleaning)

This method of cleaning uses traditional solvents
in their liqujd form rather than their vapor form to
clean the workpiece. This is a common practice in
painting operations. Typically, solvents such as
methyl isobutyl ketone (MIBK), methyl ethyl
ketone (MEK), or 1,1,1 trichloroethane are used.
The primary advantage of this method is its
versatility. Liquid solvents can be used to clean an
entire part by spraying or immersing the part in
the solvent, or by wiping with a rag. Typically,
 this process is used to clean small workpieces
 rather than parts that are large or have complex
 geometries.

 Like vapor degreasing, capital costs for cold-
 solvent degreasing generally are low, and the
 system requires minimal equipment, floor space, ,
 and training. Also, spent solvent can be distilled
 and recycled onsite. In states where the solvent is
 regulated as hazardous material, however, most
 facilities send'exhausted cleaning solution offsite
 to commercial recycling operations. Assistance
 providers should be aware that special safety
 equipment is required by OSHA for distillation
 systems.
                                             32

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                                                                     Chapter. 5: Surface Preparation
 As with vapor degreasing, the principal limitation,
 of cold solvent cleaning is that emissions from the
 solvents can be damaging to the environment, and
 may pose a threat to human health. Other limita-
 tions include:                               •
 + Moisture can form on the workpiece and
  " cause rusting problems when solvent evapo-
   rates too quickly.
 •* Same solvents can leave a residue that re-
   duces the adhesion of the coating.
 * Solvents with low flashpoints can be fire
   hazards.          ,-

 Best Management Practices for Cold
 Cleaning

 Best management practices for enhancing effi-
 ciency in the cold cleaning process include the
 following:            "
 * To minimize emissions, cleaning operations
   should be done in an enclosed area; if the
   solvent used is heavier than water and not
  • miscible, a water cover should be used as a  .
  . vapor barrier.
  * Solvent should be replenished using an
   enclosed pump system.   ,
  * Consider recommending the use of several
   tanks that extend the period belween solvent
   changes (EPAr, p. 83).
  + Investigate alternative solvents. A variety of less
   toxic solvents are available and are potentially
   effective substitutes. A recent U.S. Army study
   identified the .following odorless hydrocarbons
   with  d-limonene as alternatives to Stoddard
   ' solvent: Breakthrough, Electron 296;Skysol
    100;Skysol,andPF.
-  For many facilities, the most effective way to
  reduce waste from cleaning operations is to invest
  in a new cleaning method. The following section
  provides information on alternatives to solvent
  degreasing.

  Alternative Gleaning

  Methods

  Aqueous  Cleaning

  Aqueous cleaning involves the use of solutions
  which are largely made up of water, detergents,
  and acidic or alkaline chemicals rather than
solvents. Typically, aqueous cleaning solutions
contain at least 95% water. Solutions that include
larger percentages of other compounds, including
terpenes and other solvents, typically are called
semiaqueous (Freeman, p. 707).

Both aqueous cleaning and semiaqueous cleaning
are usually more environmentally friendly than
traditional solvent cleaning and adapt to a wide
variety of cleaning needs. Aqueous cleaning is
usually used after mechanical cleaning. A spray,
dip, or a combination of both is typically used,
depending on the workpiece. The particular
solution selected depends on both the type of
contaminant and the type of process equipment
used (EPAli, p. 13). Elevating the temperature of
  CASE STUDY:
  Ball Metal Container Group,
                        ^

  Ball Metal Container Group of Findlay, Ohio,
  produces 12-ounce aluminum beverage
  cans, drawn and ironed containers, and
  easy-opening ecology ends. The company
  has virtually eliminated the use of solvent-
  based materials by switching to .water-based
  products, for its cleaning needs. In October
  1990, Ball voluntarily stopped using 1,1,1-
  trichloroethane to clean parts and printing
  blankets, opting instead for a substitute qf
  alcohol and a water-based Simple Green
  solution (OH EPAd).
 the solution can make it more effective in remov-
 ing greases and oils, which have increased mobil-
 ity at higher temperatures (KSBEAP,.p. 2).
 However, solutions that have too high a tempera-
 ture may set some soils and make them more
 difficult to remove.

 Advantages and Disadvantages

 Aqueous cleaning can be used on a wide range of
 substrates and is less toxic than solvent processes.
 Some disadvantages include a high rate of water
 consumption and hazardous wastewater discharge
 (Freeman, p. 707). In addition, some acids used in
 aqueous cleaning can cause hydrpgeri
 embrittlement, reducing the strength of metal
 substrates'(KSBEAP, p. 2). Ferrous parts need to
 be dried rapidly to avoid rusting. .
                                             33

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Chapter 5: Surface Preparation
Aqueous Cleaning Processes

The conventional aqueous cleaning processes are
vibratory deburring and hand-aqueous washing,
although automated and power washing processes
are available.

In vibratory deburring, soiled parts are placed in
an open vessel with an aqueous cleaning solution.
The vessel is then rotated, which rumbles the
parts. The cleaning solution is removed and clean
tap water is added to rinse the parts (Freeman, p.
470-472). In this method, the part is simulta-
neously cleaned and deburred.

In hand-aqueous washing, parts are dipped by
hand into a series of tanks containing surfactant
solutions and rinsewater. A continuous clean water
flow must be maintained in the final rinse tanks,
but the surfactant and other rinse tanks (also
known as drag-out tanks) can be used for an.
entire day without changing the solutions (Free-
man, p. 470-472).

The most common automated aqueous washer
used in coating operations is a 3- to 7-stage spray
washer which uses an overhead conveyor and
racks to move the parts. Belted conveyor spray
washers are also common, as are multistage
agitated immersion washers of various types.
Centrifugal washers can be part of an automated
aqueous system, but they are uncommon in
coating pretreatment systems (Callahan, 1997).

Process Optimization
A number  of other processes used as part of an
aqueous c leaning system can enhance cleaning
effectiveness. These include high-pressure sprays,
 mechanical agitation, and ultrasonic methods. In
 fact, in the manufacturing environment, many
 aqueous cleaning systems are multistaged and ,
 include several different processes (Levitan et al.,
 p. 54).

 Ultrasonic cleaning uses high-frequency sound
 waves to improve the efficiency of aqueous and
 semiaqueous cleaners. By generating zones of
 high and low pressures in the liquid, the sound
 waves create microscopic vacuum bubbles that
 implode when the sound waves move and the
 zone changes from negative to positive pressure.
 This process, called cavitation, exerts enormous
localized pressures (approximately 10,000 psi)and
temperatures (approximately 20,000°F on a
microscopic scale) that loosen contaminants and
actually scrub the workpiece (Freeman, p. 472). A
typical ultrasonic system moves the pieces through
three stages: an ultrasonic cleaning tank containing
a water-based detergent; two rinse tanks; and a
drying stage (Levitan et al., p. 57). Ultrasonic
cleaning can be used on ceramics, aluminum,
plastic, and glass, as well as electronic parts, wire,
cables, rods, and detailed items that might be
difficult to clean by other processes (Freeman, p.
472).

Other  Cleaning Methods .

The methods described below are not widely used
to clean metal parts. However, they can be used
as substitutes for conventional solvent vapor
degreasing.

' Vacuum De-o///ng. This method uses a vacuum
furnace and heat to vaporize oils from parts.
Vacuum furnace de-oiling can be applied where
vapor degreasing typically is used to clean metal
parts. It also can remove oil from nonmetallic
parts. Although capital costs for vacuum de-oiling
 are high, the operating costs are low. Unlike other
 clean technologies, vacuum de-orling does not
 leave the cleaned parts water soaked, so they do
 not need to be dried. Because the time and
 temperature of the de-oiling process depends on
 the material to be cleaned and the oil to be
. removed, adjustments might be needed for each
 new material, oil, or combination. Also, the parts
 must be able to withstand the required tempera-
 ture and vacuum pressure (Freeman, p. 478-479).

 Laser Ablation. In this method, short pulses of
 high-peak-power laser radiation are used to rapidly
 heat and vaporize thin layers of material surfaces.
 Laser ablation can perform localized cleaning in
 small areas without affecting the entire part. Laser
 ablation does not use solvents or aqueous solu-
 tions and therefore generates little hazardous
 waste. The only waste generated is the small
 amount of material removed from the surface of
 the item being cleaned (Freeman, p. 479). Laser
 ablation has been used to strip paint from aircraft.
 At the other extreme, it has been used to remove
 sub-micron particles and thin fluid films from
 semiconductor components (SHWEC, p. 16).
                                              34

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                                                                       Chapter 5: Surface Preparation
Table 8. Alternatives to Chlorinated Solvent Cleaning (NFESC)
Contaminant
Corrosion Inhibitors
Fats and Fatty Oils
Fingerprints
Ink Marks
Hydrocarbon Greases
and Oils
Machining (cutting fluids)
Polishing Compounds
Possible Alternatives ,
> Alkaline-soluble compounds
* Hand wipe or use alkaline cleaners .
'«• Handle all fabricated parts with gloves .••.•..
> Use alkaline compounds for hand wiping
* Use alcohols with hand wiping ,
«• Use water-soluble inks and remove ink with water
* Use labels or tags until final marking is applied
> Institute the use of hand wiping stations to remove enough soil for
alkaline cleaning " • ,
* Use water-soluble compounds
•* Substitute water-soluble fluids for use in machining
* Use water-soluble compounds
* Clean at polishing station •'",••
Supercnf/ca/ Fluid Cleaning.This process
involves the application of fluids at temperatures   .
and pressures above their critical point to remove
contaminants from parts. CO2 is the most com-
monly used fluid in this process because it is
widely available and considered to be nontoxic.
Supercritical fluid cleaning is compatible with
stainless steel, copper, silver, porous metals, and
silica. It leaves no solvent residue after cleaning
and has low pperating costs. However, capital
costs are high (e.g., $ 100,000 for small-capacity.
equipment) (Freeman, p. 708-709). Therefore,
supercritical fluid cleaning has been used mainly in
.precisioncleaning(EPAh,p.27). '•  •

Alternative  Cleaners

 With the phase.out of chlorofluorocarbon (CFC)-
 based cleaners, there has been an increased
 interest in investigating alternatives to these
 chemicals. Table 8 lists typical soils and alternative -
 cleaning methods that are effective in reducing the
 use of chlorinated solvents.

• Chemical  Alternatives

 Many alternatives to methylchlorofluorocarbons
 (MCF) and CFC-113 are available for use in cold
 cleaning and vapor degreasing applications such as
 wipe cleaning, dip cleaning, immersion soaking,
 pressure washing, and vapor degreasing. Some
 solvents are recommended only for specific
 applications while others are used for many      .
 applications. In general, the following properties
 are desirable when considering solvent alterna-
 tives: low surface tension to penetrate small     .
 spaces, high density to remove small particles,
 high volatility to provide rapid drying, non-VOC,
 good solvency to readily improve organic soils,
 low cost, low toxicity, nonflammable, little resi-
 due, and easy cleanup and disposal (NFESC).

 ' Drop-in solvent replacements for traditional
 solvents such as MCF and CFC-113 usually are
 not possible. However, because vapor degreasing
 is effective in cleaning delicate parts,_some
 facilities might want to consider maintaining the •
 process with a substitute solvent. Some possible
 CFC-free alternatives include:

'•'•* D-Limonene
 •  Common D-limonene solvent blends have
 •  flashpoints higher than T40°F. Therefore, they
   do not pose an ignitability hazard.
                                              35

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Chapter 5: Surface Preparation
  N-methyl-2-pyrolidone
  Also known as M-pyrol or NMP, N-methyl-2-
  pyrolidone has high purity, a high flash point,
  and low volatility. It is very effective in ultra-
  sonic applications'.

•••Volatile Methyl  Siloxanes
  Volatile methyl siloxanes (VMS) compounds are
  relative newcomers to solvent cleaning. They
  are low molecular-weight silicone fluids
  available in a variety of blends, exhibiting
  good compatibility with plastics and elas-
  tomers. However, all blends are either flam-
  mable or combustible, and somewhat toxic.
  Advantageous characteristics of VMS include
  good cleaning capabilities for a wide variety
  of contaminants, rapid drying without leaving
  residue on the workpiece, rapid spreading,
  and good penetration into tight spaces. Also
  VMS can use existing equipment. Finally, VMS
  fluids can be distilled for reuse.

 * Hydrochlorofluorocarbons
  While hydrochlorofluorocarbons (HCFCs) are
  similar to CFC-113 and MCF  in solvency and
 , cleaning effectiveness, the use of HCFCs is
  severely restricted because of their ozone-
  depleting potential and negative health effects.
  A production ban on HCFCs is scheduled for
  the year 2010, and could be accelerated at
  any time. Emission controls are also required
  for safe operating conditions (NFESC).

 ^Aliphatic Hydrocarbons
   Aliphatic compounds comprise a wide  range
   of solvents such as mineral sprrits and kero-
  .sene. These solvents' have superior cleaning
   ability and are compatible with most plastics,
   rubbers, and  metals, and are reusable when
   distilled. However, aliphatic hydrocarbons are
   flammable, slow to dry, and have low occupa-
   tional-exposure limits. Because of this fact,
   aliphatics have not been considered a  desir-
   able substitute for traditional solvents.

  *Other Organic Solvents              ,   •
   Organic solvents, such as ketones; alcohols, •
   ether, and esters, are effective but dangerous.
   Many are HAPS while others  have very low •
   flash points. For example, acetone has a
   flashpoint of 0°F. Extreme caution is required
  when handling these organic solvents. In
  addition, organic solvents can be toxic and
  malodorous and, as a result, are not generally
  used in vapor degreasing. Another major
  concern is fire danger. Also,' in development
  are hydrofluoroethers (HFE) and
  perfluorocarbons. These contain no VOCs '
  and are not considered ozone depleting
  chemicals (ODC). EPA has approved them for
  use underthe Significant-New Alternatives
  Program (SNAP). These chemicals are more
  volatile than 1,1,1 trichloroethane and CFC-
   11 3 and would serve as an ideal replacement
  when quick drying, is important (EPAq, p.  32).

 Some companies have begun using other HCFC
 solvents such as trichlofoethylene, perchloroethyl-
 ene, and methylene chloride. These solvents have
 been used often in vapor degreasing because of
 their similarity to CFC solvents in both physical
 properties and cleaning effectiveness. However,
 using these alternatives has significant disadvan-
 tages for the facility. All of the above three
 alternatives have been classified as Hazardous Air
 Pollutants (HAPs) by EPA and are targeted by the
 Emergency Planning and Community Right-to- .
 Know Act as well. Furthermore, these spent
 solvents are classified as a hazardous waste. As a
 result, handling and disposal of these solvents is
 complicated and more expensive.

 Once a part has been cleaned,.it can receive a
 conversion coating prior to the painting process.
 The next section provides information on conver-
 sion coatings and techniques to reduce waste-from
 these processes.

  Conversion Coatings

  Chemical and electrochemical conversion treat-
  ments provide a coating on metal surfaces to
  prepare the surfaces for painting. These conver-
  sion treatments include anodizing and phosphat-
  ing. Conversion coatings are usually confined to
•  large operations with elaborate, waste-treatment
  facilities because of extensive regulations control-
  ling disposal of rinse water and sludges containing
  heavy metals.

  Anodizing
  Anodizing is a specialized electrolytic  surface
  finish for aluminum that imparts hardness and
                                             36

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                                                                       Chapter 5: Surface Preparation
     P2 Tips for Conversion Coatings

 * Avoid soiling the substrate prior to the
   cleaning process.
 * Analyze water for hardness and dissolved
   solids. Use alkaline cleaners or phosphate
   compounds with hard-water stabilizers .
   when necessary.
 * Use fow-temperature, energy-conserving,
   alkaline cleaners or phosphate compounds.
corrosion resistance, increases paint adhesion^
provides electrical insulation, imparts decorative
characteristics, and aids in the detection of surface
flaws on the aluminum. This process employs
electrochemical means to develop a surface oxide
film on the workpiece, enhancing corrosion  _
resistance. Anodizing is a similar process to
electroplating but it differs in two ways. First, the
workpiece is the anode rather than the cathode as
in electroplating. Second, rather than adding
another layer of metal to the substrate, anodizing
converts the surface of the metal to form an oxide
that is integral to the substrate (SME, 1985).

Industry uses three principal types of anodizing:
chromic-acid anodizing (called Type I anodizing),
sulfuric-acid anodizing (called Type II anodizing),
and hard-coat anodizing, which is a combination
of sulfurie acids with an organic a'cid such as
. oxalic acids (called Type III anodizing). Because
of the structure, the anodized surface can be dyed
easily. These dyes include organic or organometal-
lic dyes and often contain chrome in the trivalent
state. Whether the pieces are dyed, they need to
be sealed. Sealing can be performed withhot
water, nickel acetate, or sodium dichrpmate, .
depending on the required properties (SME,
•1985),

VType 1 (Chromic Acid) Anodizing: Chromic-
   acid anodizing takes place in a solution of
  . chromic acid. The hexavalent chrome solution
   creates a thin  hard coating (Ford, 1 994).

,+ Type II (Sulfurie Acid) Anodizing: Sulfuric-acid
   anodizing takes place in a 15% solution of
,  • sulfurie acid. During the anodizing process,
   aluminum dissolves,off the surfdce of the part
   and changes the surface characteristics to an
  ' oxide coating. This process creates a surface
   structure  that is. both porous arid harder than
  the base aluminum. Sealing of this coating
  provifjes greater corrosion protection. When
  the aluminum concentration in the bath solu-
  tion builds up to a certain level ,(-15 to 20
  grams per liter), the process becomes less
.  efficient and requires treatment (Ford, 1994).

 *Type.ll) (Hard Coat) Anodizing: Hard-coat  ,,
  anodizing is'a form of sulfuric-acid anodizing'
  in which the acid-content is slightly higher
  (20%) and an organic additive is added to the
  bath. This additive helps to create a tighter
  pore structure that increases the hardness of
  the oxide coating. Hard-coat anodizing has a
  high resistance to abrasion, erosion, and
 • corrosion. This type of coating also can be   '
  applied in much thicker layers than'Type I or
  Type II anodizing (Ford,  1994).

 Various methods are used to treat wastes gener-
 ated from anodizing bath solutions. Technologies
 that have been employed successfully include:
 evaporation systems operating under reduced
 pressure, sedimentation, reverse osmosis, filtra-
 tion, and anion  and cation exchangers.

 Substituting.Type I Chromic-Acid Anod-
 izing with Type II Sulfuric-Acid Anodizing

 Because of federal and state mandates imposed on
 operations using hexavalent chrome, researchers
 have investigated the feasibility of substituting
 Type I anodizing with Type II sulfuric-acid
 anodizing. A NASA study found that in applica-
 tions where anodizing is used to impart corrosion •
 protection on aluminum, Type II sulfuric-acidj
 anodizing is superior to Type I chromic-acid
 anodizing (Danford, 1992).            '

 According to suppliers, conversion from chromic-
 acid to sulfuric'-acid anodizing is not a simple
 chemical substitution: The conversion requires a
 complete-changeover of anodizing equipment and
 partial modifications to downstream waste-
 treatment facilities. Replacement of the anodizing.
 tank often is required because of the differences in
 material compatibility between the tank (and tank
 liner) and sulfurie acid and chromic acid. Sulfuric-
 acid anodizing processes also have different
 •voltage and amperage requirements, necessitating
 replacement of the rectifier. The operating tem-
 perature of the;electrolytic bath also is different
 for the two processes. The chromic process is
                                              37

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Chapter 5: Surface Preparation
  CASE STUDY:
  Substituting Chromic Anodizing with
  SulfuricAcid

  In December 1 988, General Dynamics
  replaced a 35-year-old chromic-acid/alumi-
  num-anodizing system with a new sulfuric-aeid
  anodizing system that used computerized
  hoists and on-demand rinsing. The new
  system, supplied by NAPCO, Inc., enabled
  General Dynamics to eliminate a major
  source of chromium emissions. In addition to
  the chemical substitution which eliminated
  chromium releases, automated hoist and on-
  demand water rinse systems helped to reduce
  wastewater treatment requirements.. The
  computerized automated hoists'monitor the
  time intervals during which the parts are
  treated  and allowed to drain. Compared vyith
  manual immersion and draining of parts, this
  system reduces treatment requirements by
  avoiding unnecessary dragout of immersion
  fluids to downstream rinse tanks. Subse-
  quently, the on-demand water system reduces
  rinsewater use and wastewater treatment
  requirements by reducing water consumption
  and monitoring the conductivity of the
  rinsewater in the tank. Unlike manually-
  operated rinse tanks, which have constant
  overflows, the on-demand system adds water
  only when the conductivity of the tank exceeds
  a set value (US EPA 1995).	'
 usually maintained by steam heat at an operating
 temperature of 90 to 1.00°F whereas the sulftiric
 acid process must be chilled.using cooling water to
 an operating temperature of 45 to 70°F.
 Operation and maintenance costs are typically
 mUch lower for sulfuric-acid anodizing than for
 chromic-acid anodizing because of lower energy •
 requirements. Wastewater treatment costs are
 lower as well because sulfuric acid only requires
 removal of copper whereas chromic acid requires
 more complex chrome reduction techniques. The
 change in materials also means that the cost of
 sludge disposal is greatly reduced.

  Sulfuric-Acid Anodize Regeneration with
  Ion Exchange
  Traditionally, facilities use'ion exchange to remove
  metallic contaminants from wastewater streams.
However, ion exchange resins also remove the
hydrogen and sulfate components of the sulfuric
acid/aluminum anodizing solution. As the solution
passes through the columns, the acid is removed.
Then the waste stream, which consists of a small
amount of acid plus all the aluminum from the
anodizing solution, flows to the wastewater
treatment system. To recover the acid, platers use
water to flush the acid components from the resin.
This forms a sulfuric acid solution that is low in
dissolved aluminum and can be used again in the
anodizing process (Ford, 1994).

Sulfuric-Acid Anodize Regeneration  with
Electrodialysis

Electrodialysis removes metal ions (cations) from
solutions using a selective membrane, an electrical
current, and electrodes. This technology uses a
chemical mixture (catholyte) as a capture and  '
transport media for metal ions. This catholyte
forms a metal sludge and requires periodic
change-outs. The recovered sludge is hazardous,
and companies might want to work with an
outside firm to recover the metal in the sludge.
Using electrodialysis, facilities can remove all the
metal impurities from the anodizing bath, main-
taining the bath indefinitely. By keeping the
concentration of contaminants in the process bath
 low, the rinsewater potentially can be recycled
 back to the bath, closing the loop on the process.
 The cost to operate this system depends on the
 size of the acid anodizing bath, the level of metal
 concentration, the metal removal capacity of the
 electrodialysis unit, and the company's ability to
 reclaim metals in the sludge.

 Alodine
 Alodine is a nonelectrolytic process used to create
 a chrome oxide film similar to anodizing. It is
 widely used in military and aerospace applications.

 Phosphate  Coatings

 Phosphating is used to treat various metals
 (mainly steel and iron) to impart corrosion resis-
 tance and to promote the adhesion of finishes
., such as paint and lacquers. Phosphating treat-
 ments provide a coating of insoluble metal-
 phosphate crystals that adhere strongly to the base
 metal. Generally,-phosphating solutions are
  prepared from liquid concentrations containing
                                             38

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                                                                       Chapter 5: Surface Preparation
one or more divalent metal's, free phosphoric acid,
and an accelerator (Ford, 1994).

The phosphating process consists of a series of
application and rinse stages typically involving the
application of either an iron, manganese, or zinc
phosphate solution to a substrate. A simple iron
phosphating system is composed of two stages: an
iron phosphate .bath that both.cleans the part and
applies the conversion coating followed by a rinse
bath to remove dissolved salts from the treated
surface. An advanced zinc phosphating line might
feature seven stages of spray/dip and rinse baths.
.-In addition, a final rinse in a low-concentrate
 acidic ehromate or an organic nonchromate
 solution is often used to further enhance corrosion
resistance and seal the coating. Following the
 conversion application, the parts are dried to
 prevent flash rusting (Ford, 1994).

 Iron and zinc phosphate coatings often are used as
 paint bases, and manganese phosphate coatings
 are applied chiefly to ferrous parts for break-in
 and galling (e.g., to engine parts). The choice of
 iron or zinc phosphate coating depends on product,
 specifications. In general,"the more extensive
 multistage zinc phosphate processes provide better
 paint adhesion, corrosion protection, and rust
 protection than iron phosphate processes. Zinc  .
 phosphate baths, however, tend to.be more
 expensive, require more maintenance, and often
 result in more sludge disposal (SME, 1985).

 Phosphate  Coatings  for Steel

 Iron or zinc phosphate coatings are usually used
- for steel. In  the phosphating process, acid attacks
 the metal surface, forming a protective coating of.
  iron or zinc phosphate salts. Zinc phosphate forms
  finer, denser crystals than iron phosphate.and has
  better corrosion resistance and paint adhesion.
  Accelerators and oxidizers are added to the
  phosphating solution to improve its effectiveness.
  Molybdic acid, added for corrosion inhibition,
  gives a purple cast to iron phosphate coatings. A
  clean surface is critical to successful application of
  the phosphate coating (KSBEAP. p.3).   .

  Process time, temperature, and chemical concen-
  tration affect the acid's reaction with the steel
  part. Process time is usually fixed because the line
must run at a certain speed, however, temperature
can have a great effect on the phosphating pro-
cess. In order for ithe process to run at optimum
efficiency, the temperature/preceding the phos-
phating process should be higher than the tem-  ,
perature required for phosphating. This allows the
part to become heated prior to entering the
phosphating process. If the part is not heated prior
to phosphating, process efficiency is reduced. For
example, if deposition efficiency is reduced,
additional chemicals may be required, and more   .
sludge could be generated. Iron phosphating
solutions typically operate between 120 and
140°F, but can also be operated at room tempera-
ture.

Cleaning and irbaphosphating can be combined in
a single solution, however, this is usually success-
ful only when the parts are lightly soiled. It is not
possible to use a combination process with zinc
phosphating (KSBEAP, p. 3).

Phosphate  Coatings  for'
Aluminum

 Iron and zinc phosphate coatings are used on
 aluminum parts or products. The choice of
 solution largely depends on the volume of alumi-
 num in the process. When a company is process-
 ing a small amount of aluminum, the same
 phosphating solution is typically used for all metals
 that are processed. For instance, if a company
 processes mainly steel and a small volume of  .
 aluminum, iron phosphating will be the' only
 process used.

 Iron phosphating solutions can effectively clean
 the surface of aluminum and improve paint
 adhesion. However, they leave little or no c.oating
 on the substrate. In order to etch the aluminum, a
  fluoroborate or fluoride additive is required.

  Companies often use chromium phosphate coating
  for small volumes of aluminum. Often, no.-rinse
, chromium phosphate solutions are'us'ed because
 . they have the advantage of not being classified as
  a hazardous waste. However, they typically  . .
  provide less corrosion resistance due to incom-
  plete coverage. Chromic acid sealers can be used
  but they contain hexavalent chromium (KSBEAP,
•  P-3)-- ,   .          ••-.•.'.
                                               39

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Chapter 5: Surface Preoaration
Issues  with  Pretreatment  Coatings

The most common problems associated with
chemical pretreatment systems are poor adhesion
and premature corrosion failure. Frequently these
problems are caused by the following:

Residual soils: These soils may be caused by
(1) conveyer line speed that exceeds the design
limits of the cleaning system, causing low dwell
time, (2) inappropriate cleaner for the soils
present, and (3) incorrect temperature for the
cleaner being used. Generally, high temperatures,
120 to 13 0°F, are best for good cleaning unless
the facility is using a low-temperature cleaner. In
that case, high temperatures can be detrimental.
To determine the cleaning temperature that
removes the soil from the parts, the operator can
immerse an uncleaned part into a container of
water and begin heating it. The operator should
use a thermometer tp watch the temperature rise
while keeping an eye on the point where the water
line touches the part. At some point, the water will
become hot enough to visibly loosen the soils,
causing globules to float to the surface (CAGE).

1 Flash rust: This  can be caused by (1) excessive
line speeds that prevent adequate exposure to the
sealer in the final rinse, (2) line stops that overex-
pose parts to chemicals or allow them to dry off
between stages, and (3) lack of sealer in the final
rinse. When using a solvent-type cleaning systenj
or an iron phosphate conversion process, wiping
with a clean, white cloth is an ideal way to check
a part's cleanliness before coating (CAGE).

 Aluminum oxide:  A natural oxide is present on
the surface of aluminum parts. This oxide
 interferes with adhesion if it is not rempved. If a
 facility is using a combination of iron phosphate
 and cleaner to remove this oxide, they should be
 certain that the combination is made for steel and
 aluminum. Their chemical supplier can discuss •
 this with them in more detail (CAGE).

 Inadequate rinsing: This is one of the most
 common mistakes made in metal cleaning. It is
 caused by both increased line speeds that reduce
 rinse-s.tage dwell time and inadequate rinsewater
 overflow. Simple tests for inadequate rinsing can.
 include slowing down the production line or hand-
 rinsing parts in deionized water. If the technical
assistance provider suspects that the company's
surface preparation system is causing a problem,
they should suggest that the company clean test
parts with clean rags dipped in a solvent, instead   •
of running the parts through their normal cleaning
process. If this fixes the problem, the firm should
focus their investigation on the surface preparation
system. If they are getting premature and massive
lifting of the coating after exposure to water due to
exterior weather elements, or after slat-fog tests,
this can indicate inadequate rinsing. Water-soluble
crystals (salts) are probably present at the coating
and metal interface. Moisture can dissolve these
salts quickly.  When this happens, rapid undercut-
ting of the film occurs and significant rust forms
(CAGE).

Pollution  Prevention  in  the
Phosphating Process         /      .

Reduced water use is the primary waste reduction
option for phosphatizing. The water added to
maintain the solution in the phosphatizing bath can
be reduced by analyzing and controlling the
solution's temperature, chemical concentration,
and pH level in each step, and recirculating
solution or rinse water from one bath to others
when possible. This option also reduces chemical
use (Ohio EPA, p. 1). A facility should analyze
incoming water quality. City water can bring in
considerable amounts of dissolved solids, and
these contaminants can vary seasonally. The  .
contaminant can have a damaging effect  on
control regimes. Determining control set points,
and treating and conditioning incoming water is a
good idea.

Properly matching the phosphating chemicals with
the metal substrate is another key issue in mini-
mizing waste from phosphating operations. This
can significantly minimize sludge generation. For
example, processing galvanized steel in an iron
phosphate solution results in excess generation of
zinc sludge because the acid reacts with  the zinc in
the substrate.

 Ultrafiltration to Maintain Phosphating
 Baths
 PrecipitateS'Continuously form in phosphating
 operations, primarily on the heating coils in the
 tanks. This presents challenges in maintaining the
 baths and often results in dumping of the solution.
                                             40

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                                                                        Chapter 5: Surface Preparation
 When the solution is removed from the tank, this
 accumulation of sludge must be manually re-
 moved. The solution should be decanted back into
 the tank to minimize waste, but because this
 requires space and time, it is rarely done. A more
 efficient system involves the use of a continuous '
 recirculation system through a clarifier with gentle .
 agitation in the sludge blanket zone. This allows  .
 for indefinite use of the solution and e.asy removal
 of dewatered sludge from the bottom of the
'clarifier (Steward, 1985).      ?

 Stripping

 Various methods are available for removing old
 paint from metal substrates. In some cases,
 stripping also functions as a cleaning method to
 remove oils, greases, or other contaminants.
 Chemical stripping has been used in a number of  •
 applications, but there are alternative methods that
 are less toxic and less costly! Alternatives to
 chemical stripping include plastic media, sodium
 bicarbonate, wheat-starch, and carbon-dioxide
 blasting, as well as high-pressure water, high-
 energy light, mechanical, cryogenic, and high-
 temperature thermal stripping. Key factors that
 must be considered when selecting a paint-
 stripping method include: the characteristics of the
 substrate to be stripped; the type of paint to be
 removed; and the volume and type of waste
 produced. Waste type and volume can have a
 major impact on the cost and.benefits associated
 with a change (MnTAP, p. 2). The following
 section describes conventional chemical stripping
 and the-alternatives.          /          .

 Chemical  Stripping

 The conventional method for removing paints
 from metal surfaces is chemical stripping. This
 process may involve applying solvents by hand
  directly to a coated surface. The solvents soften
  or dissolvethe coatings and are usually scraped
 - away or otherwise mechanically removed  (Free-
  man, p. 704-705). Facilities often use a water
  rinse for final cleaning of the part (EPAg,  p. 2).-
  Disassembled parts may be stripped in an  immer-
  sion tank. Immersion strippers are advantageous
  because they can strip paint from recessed and
 • hidden areas. This is not possible with abrasive .
  blasting methods.               .   ,
Chemical-based paint strippers are either hot (i.e.,
heated) or cold. Many hot strippers use sodium
hydroxide and other organic additives. Most cold
strippers are formulated with methylene chloride
and other additives such as phenolic acids,   '
cosolvents, water-soluble solvents, thickeners, and
sealants. Handling and disposal of spent baths and
rinses is a major problem for facilities employing
both types of strippers (Freeman, p. 704-705).

Many new stripping formulations have been
developed including strippers based on formula-
tions ofN-methyl-2-pyrollidone (NMP) and
dibasic esters (DBE). Althpugh these new strip-
pers are used in the consumer market, they have
not been accepted for use in.industrial stripping
operations because their effectiveness varies from
paint to paint. Compared to the stripping achieved.
. with formulations containing methylene chloride
 and phenol, many of the substitutes suffer from
 one or more of the following disadvantages:
 effectiveness varies with type of paint and extent
 of cure; elevated temperature is required; and
 increased stripping time is required.  In selecting
 art alternative, technical assistance providers
 should make sure that the stripper does not attack
 the substrate or react with the substrate (i.e., is
 flammable, combustible, or photochemically
 reactive) (Freeman, p. 491-492).

 Abrasive Blasting

 Many facilities have reduced their reliance on
 chemical-based strippers by converting to abrasive
 blasting. Abrasive blasting uses mechanical energy
 to hurl particles at high speed, removing paints
 and other organic coatings from metallic and
 nonmetallic surfaces (Freeman, p. 704).      •

 Abrasives commonly used for stripping include'
 steel grit, alumina, garnet, and glass beads. Steel
 gritcreates a rough surface profile on the substrate
 which aids coating adhesion. Because it is so hard
  and durable, steel grit can be reused repeatedly,
  and it generates the least amount of waste per unit
  of surface area stripped. To maximize the reuse of
  steel grit, companies must keep the blast media
  dry to avoid rusting. Alumina is considered to be a
  multipurpose material that is less aggressive and
  less durable than steel grit, and it results in a
  smoother surface profile and less removal of
  substrate material. Garnet and glass beads are the
                                                41

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Chapter 5: Surface Preparation
 least aggressive abrasive and often are used in a
 single-pass operation (i.e., the abrasive is not
 recycled). Use of garnet and glass beads is most   .
 suitable for preparation of soft materials that are
 easily damaged, and for maintenance of the
 dimensional tolerance of the part (Freeman, p.
 490-491).

 Types  of Abrasive Blasting

 Companies can use abrasive blasting to remove
 paint from larger metal structures in the field (field
 stripping) or from smaller metal structures in a
 hanger, booth, or blasting cabinet.

 Field stripping can be performed in an open
 area. Operators must wear self-contained breath-
 ing equipment in order to be protected from the
 stripping dust. After blasting, the used abrasive
 can be shoveled or vacuumed from the area and
 processed through the reclaimer. Some systems
 combine dust control and abrasive recovery by
 including a vacuum collection pickup device with
 the blasting nozzle (Freeman, p. 490-491).

 Blast stripping in  cabinets is often performed
 using manual blast cabinets and automated
 blasting chambers to remove paint from parts.
'The abrasive is fed into the cabinet or chamber
 and directed against the part being stripped. Used
 abrasive and removed paint are then pneumati-
 cally conveyed to a reclaimer. Reusable abrasive is
 separated from the waste and fines (broken-down
 abrasives and paint chips) are collected in a dust
 collector (Freeman, p. 490-491).

 Process Optimization

 Because the main advantage of chemical-based
 strippers is their inability to scratch or damage the
 substrate, most of the abrasives that companies
 consider as feasible substitutes are relatively soft
 materials. Glass-bead blasting has become popular
 because it is the least aggressive of the commonly
 used abrasives. New alternatives include plastic
 media, wheat starch, ice crystals, carbon dioxide
 pellets and sodium bicarbonate slurry (Freeman,
 p. 490-491). The major disadvantage with these
 processes is that they can only be used for line-of-
 sight stripping.
 Plastic media blasting

 Plastic media blasting (PMB) is an abrasive
 blasting process designed to replace chemical
 paint-stripping operations and conventional sand
 blasting. This process uses soft, angular plastic
 particles as the blasting medium. PMB is .per-
 formed in ventilated enclosures such as small
 cabinets (a glove box), a walk-in booth, a large
 room, or airplane hangers. The PMB process
 blasts the plastic media at a much lower pressure  -
 (less than 40 psi) than conventional blasting. PMB
 is well suited for stripping paints, because the low
 pressure and relatively soft plastic medium have a
 minimal effect on the surfaces beneath the paint
 (TSPPO).

 Plastic media are manufactured in 6 types and a
 variety of sizes and hardness. Military specifica-
 tions (MIL-P-85891) have been developed for
 plastic media. The specifications provide general
 information on the types and characteristics of
 plastic media. The plastic media types are:

 Type I  Polyester (T-hermoset)
 Type II Urea formaldehyde (Thermoset)
 Type 111 Melamirie formaldehyde (Thermoset)
 Type IV Phenol formaldehyde  (Thermoset)
 TypeV Acrylic (Thermoplastic)
 Type VI Polyallyl diglycol carbonate (Thermoset)

 Facilities typically use a single type of plastic
 media for all of their PMB work. The majority of.,
 DOD PMB facilities use either Type II or Type V
 media. Type V media is notas.hard as Type II
 media and is gentler on substrates. Type V media
 is more commonly used on aircraft. Type II is
 better suited for steel-only surfaces (TSPPO).

 After blasting, the PMB media is passed through a
 reclamation system that consists of a cyclone
 centrifuge, a dual adjustable air wash, multiple
 vibrating classifier screen decks, and a magnetic
 separator. In addition, some manufacturers
 provide dense particle separators as a reclamation
. system. The denser particles, such as paint chips,
 are separated from the reusable blast media, and
 the reusable media is returned to the blast pot.
 Typically, media can be recycled 10 to 12 times
 before becoming too small to remove paint
 effectively (TSPPO).
                                              42

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                                                                       Chapter 5: Surface Preparation
Waste material consists of blasting media and
paint chips. The waste material may be classified
as a RCRA hazardous waste, because of the
presence of certain metals (primarily lead and
chrome from paint pigments). An alternative
solution to handling the potential hazardous waste'
is to recycle the media to recapture the metals.
  progress in accordance with OSHA requirements
  as specified in 29 CFR 1910.94 (TSPPO).

  PMB systems can range in cost from $7,000 for a
  small portable unit to $ 1,400,000 for a major
  facility for aircraft stripping.

  Vacuum Sanding Systems
 Reusing the plastic blasting media greatly reduces    A vacuum sanding system is essentially a dry- •
 the volume of spent media generated as compared   abrasive blasting process (e.g., sand blasting or
 to that generated in sand blasting. When compared  plastic media blasting) with a vacuum system
 to chemical paint stripping, this technology
 eliminates the generation of waste solvent. PMB'is
 also cheaper and quicker than chemical stripping.
 The U.S. Air Force and airlines have found PMB
 effective for field stripping of aircrafts, but PMB
 could also be used to strip vehicles, ships, and
 .engine parts (IHWRICf). However, PMB can
 cover fatigue cracks at high blast pressures and
 prevent their detection. ,

 As with any blasting operations, airborne dust is a
 safety and health concern with PMB. Proper
 precautions should be taken to ensure that person-
 nel do not inhale dust and particulate matter.
 Additional protective measures should be taken
, when stripping lead chromate- or zinc chromate-
 based paints, as these compounds may be hazard-
 ous. Inhalation of lead and zinc compounds can
 irritate the respiratory tract, and other paint
 compounds are known to be carcinogenic. Inhala-
 tion of paint solvents can irritate the lungs and
 mucous membranes. Prolonged exposure can
 affect respiration and the central nervous system.
 Operators must wear continuous-flow airline
 respirators when blasting operations are in
  attached to the blast head that collects the blast
  media and the removed coating material (paint or
  rust). The unit then separates the used blast media
  from the removed coating material. The remaining
  blast material is recycled for further use, and the
  coating material is disposed.           '   ,    '

  This system is designed to replace chemical paint
  stripping, and has three added advantages. The
  first advantage is its collection of both the blasting
  media (sand, PMB, or other media) and its   .
  collection of the waste coating material being
  removed. The second advantage is that it sepa-
  rates the media from the waste material by a
  reverse pulse filter, and the media is reused in the
  system, thereby minimizing the quantity of media
  required. The third advantage is that, due to the
  confinement of the blast material, this technology
  may be used when it is impractical to use tradi-
  tional sand blasting or chemical stripping
  (TSSOP).

  Vacuum sanding is a stand-alone system, including
  the air compressor to drive the system. The units
   are portable (skid, mounted) and can be moved by
 Table 9. Advantages and Disadvantages of Plastic Media Blasting
 Advantages
Disadvantages
  * Can be recycled for use (10-12
   .recycling events)                       ,
   Eliminates wastewater disposal costs (typical
   in chemical paint-stripping operations)
   Eliminates production of waste solvents when
   compared to chemical paint stripping
   Has a high stripping rate '
   Has no'si'ze limitations
^Requires substantial capital equipment investment
*May generate hazardous waste
*May require different operator time, maintenance
  requirements, and handling and disposal methods
' for waste depending upon material stripped
*May limit quality depending on skill and
  experience level of the operator
*May not be used in certain military applications
  because of limits in specifications'
* May not remove corrosion
                                               43

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Chapter 5: Surface Preparation
a forklift. The air compressor is a trailer unit (2-
wheeled). The waste material may be classified as
a RCRA hazardous waste because of the presence
of metals in the waste (TSSOPj.

This technology reduces pollution because the
portable vacuum sander removes coatings and
corrosion from composite or metal structures
while capturing the media and solid waste.
Vacuum sanding eliminates airborne particulate
matter and potential lead-dust exposure hazards.
When compared to chemical paint stripping, this
technology eliminates the generation of waste
solvent (TSSOP).

Storage and handling of sand or plastic media and
blast waste- associated with vacuum sanding pose
no compatibility problems. Collection systems
should not mix different types of waste, and
should ensure that the most economic disposal
method can be obtained for each. Prior to using
plastic media for de-painting operations, personnel
should check applicable military specifications
[such as (MIL-P-85891)] and operations manuals
for the PMB systems. Some military specifica-
tions do not allow PMB for de-painting certain
types of materials (e.g., fiberglass, certain Com-
posites, honeycomb sandwich structures, and
some applications with thin-skinned aircraft
components). In certain cases, PMB can inhibit
crack detection on softer alloys used for aircraft
components (e.g.; magnesium) (TSSOP).

Airborne dust, which is an important safety and
health concern with any blasting operation, is
essentially eliminated using the vacuum blasting
system. However, in order for the vacuum system
to be effective, the vacuum and blasting head
must be kept in contact with the material being
stripped of paint or corrosion. Therefore, training
operators in the proper use of the equipment is
essential. In addition, eye protection and hearing
protection are recommended (TSSOP).

Vacuum sanding systems can range in cost from
$ 17,000 to $40,000, excluding the portable
generator to operate the system.

Sodium Bicarbonate
Sodium bicarbonate is another media that compa-
nies can use to remove paint. The process that
   Table 10. Advantages and Disadvantages of Vacuum Sanding Systems
   Advantages
  Disadvantages
   * Improves personnel safety by eliminating
     airborne particulate matter and potential
     lead dust exposure hazards
   * Eliminates the need for the use of respirators
     while blasting
   * Separates waste material from blasting media,
     therefore, the media can be recycled
   «• Is versatile and can use multiple media types
   «• Eliminates wastewater disposal costs (typical in
     chemical paint-stripping operations)
   * Eliminates the production of waste solvents
     when compared to chemical paint stripping
   * Can be portable
   *Has self-supplied power/air compressor
   *• Minimizes emissions from portable (mobile
     source) diesel air compressors so no air
     permit required
   •» Minimizes the clean-up time because blast
     material is contained
   *• Contains contaminated coatings
  * Requires substantial capital equipment
    investment
  * Requires disposal of used blasting materials
    and waste coating as a hazardous waste
  4 Requires operator training .
  +May vary operator time, maintenance
    requirements, and handling and disposal
    methods depending upon material to be
    stripped
  *• May vary quality of stripping depending on
    skill and experience level of the operator
                                             44

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                                                                        Chapter 5: Surface Preparation
uses sodium bicarbonate cart be used with or  ••
without water. However, it is most frequently
applied with water, which acts as a dust suppres-
sant. The water-based process uses a compressed
air delivery system that transfers the sodium
bicarbonate from a pressure pot to a nozzle^
where the sodium bicarbonate mixes with a stream
of water. The soda/water mixture impacts the
coated surface and removes old coatings Trom the
substrate. The water dissipates the heat generated
by the abrasive process, reduces the amount of
dust in the air, and assists in paint removal through
hydraulic action. Workers do not have to prewash
or mask the surface of the material being stripped.
The solid residue from the wastewater generated
can be' separated by filtration or settling (NFESC).
   /           '       '      '
The effectiveness of sodium bicarbonate stripping
depends on optimizing a number of operating
parameters such as nozzle pressure, standoff
distance, angle of impingement, flow rate, water
pressure, and traverse speed. In general, sodium
.bicarbonate stripping systems remove paint more
• slowly than chemical stripping. The type of
equipment used may also bring about significantly
 different results,
      i ' •                 "       • •       "    -
 Use of sodium bicarbonate in its dry form (or
 when it is not fully mixed with water) can create a
 cloud of dust that requires monitoring and may
 require containment to meet air-quality standards.
 The dust is not an explosive hazard nor is it toxic,
 but air particulates generated from stripping
 operations can contain toxic elements. This
 process should be conducted in areas where
.exhau'st particulates can be contained and/or .
 ventedto ventilation systems to remove hazardous
 airborne particulates.

 Approximately 150 to 200 pounds of bicarbonate
 is needed per hour, while PMB requires 800
 pounds. In the end, bicarbonate is,cheaper than
 PMB because it neither generates large amounts
 of waste nor damages the metal. Nevertheless,
 sodium bicarbonate can have  long-term corrosive
 effects because alkaline compounds that remain
 on the metal can foster corrosion or interfere with
 the paint bonding. Corrosion inhibitors can be
 added; however, the waste .might then become
 hazardous, depending on the type of inhibitor used
 (IHWRICf).                •
Wastewater disposal methods and sodium bicar-
bonate waste disposal methods will dependpn the,
toxicity of the coatings and pigments that are
removed in the stripping process. The waste
generated from bicarbonate of soda stripping
systems in the wet form is a slurry consisting of
sodium bicarbonate media, water, paint chips, and
residues such as grease and oil. Some facilities are
using centrifuges to separate the water from the
contaminated waste stream, reducing the amount
of hazardous waste. Filtered wastewater contain-
ing dissolved sodium bicarbonate may be treated
at industrial wastewater treatment plants. In its dry
form, the waste includes nuisance dust, paint
chips, and residues of grease and oil. This waste
may be disposed of in a solid waste landfill;
however, due to the possibility of toxics in the
paints and the presence of oils, the material should
be tested prior to landfill disposal (NFESCa, p.4).

 Wheat starch blasting .    :

 Wheat starch blasting is a user-friendly blasting •
 process where wheat starch.is used in systems
 designed for plastic media blasting, as well as
 systems.specifically designed for wheat starch
 blasting. The wheat starch abrasive media is a
 crystallized form of wheat starch that is nontoxic,
 biodegradable, and made from renewable re-
 sources. The media is similar in appearance to  .
 plastic media, but it is softer (TSSPO).  >

 The wheat starch blasting process propels the
 media at less than a 3 5 psi nozzle pressure for
 most applications. The low pressure and relatively
 soft media have minimal effects on the surfaces
 beneath the paint.' For this reason, wheat starch is -
 .well suited for stripping paints without risking
 damage to the substrate. Examples of suitable
 applications include removing paint from alumi-
. num alloys and composites like graphite and
 fiberglass (Kevlar).

 The wheat starch blasting process can remove a
 variety of coatings: Coating types range from
 resilient rain ero^ionrresistant coatings found on
 radar absorbing materials to the tougher polyure-
 thane and ep'oxy paint systems.'The wheat starch
 system has been shown to be effective in remov-
 ing bonding adhesive flash .(leaving the metal-to-
 metal bond primer intact), vinyl coatings, and
 sealants. It has also been found to.be effective in
                                               45

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Chapter 5: Surface Preparation
 Table 11. Advantages and Disadvantages of Sodium Bicarbonate (NFESCa p. 4)
 Advantages
Disadvantages
 *• Significantly reduces the amount of hazardous
   waste generated when compared to chemical
   stripping
 •*• Reduces the number of hours required for
   stripping when compared to chemical
 I  stripping
   Selectively removes individual coating layers
   Does not require prewashing and masking in
   most applications
 * Avoids size limitations for parts being stripped
   Enables wastewater stream to be centrifuged
   to reduce waste volume or to be treated at an
   industrial wastewater facility
 *• Reduces costs because  blast media is usually
   less expensive than plastic media, wheat
   starch, and carbon dioxide pellets
* Requires subsequent washing of the item; thus
  electrical components cannot be exposed to this
  stripping process
* Although the water can be separated for
 " disposal, cannot recycle sodium bicarbonate
  solution
* May require monitoring
* May require containment
 removing the paint from cadmium parts, while
 leaving the cadmium plating intact (TSSPO).
 Wheat starch blasting is mainly known for its
 gentle stripping action and is particularly suited for
 stripping operations on soft substrates,, such as
 aluminum, very soft alloysj anodized surfaces, or
 sensitive composites.

 There are several important components in wheat
 starch systems. First, a moisture control system is
 needed to control the storage conditions of the
 medium. This is especially important when the
" system is shut down for extended periods of time.
 Second, to remove contaminants from the wheat
 starch media, the spent wheat starch residue is
 dissolved in water and then either filtered or
 separated in a dense particle separator/centrifuge.
 The wheat starch media is recycled in the system
 and may be used for up to 15 to 20 cycles. Low
 levels of dense particle contamination in the media
 may result in a rough surface finish on delicate
 substrates. The waste stream produced from this
 process consists of sludge generated from the
 wheat starch recycling system. This system
 produces approximately 85% less waste sludge  '
 compared to the waste sludge produced in chemi-
  cal stripping (TSSPO).

  Wheat starch blasting can be used on metal and
  composite surfaces. Direct contact of wheat starch
 with water must be avoided to maintain the
 integrity of the blast media. Wheat starch blasting
 requires explosion protection. If conditions are
 right, a static electrical charge developed by a high
 velocity wheat starch particle in the air could ignite
 the material. Preventive measures must be taken.

 As with other blasting procedures, airborne dust is
 a safety and health concern. Proper precautions
 should be taken to ensure that personnel do not
 inhale dust and particulate matter. Additional
 protective measures should be taken when
 stripping lead, chromate, ziric chromate, or   .
 solvent-based paints, as these components may be
 hazardous. Inhalation of lead and zinc compounds
 can irritate the respiratory system and some
 compounds are known to be carcinogenic. Inhala-
 tion of paint solvents can irritate the lungs and   .
 mucous membranes. Prolonged exposure to these
 emissions can affect respiration and the central
 nervous system. Proper personal protective
 equipment should be used (TSSPO).

  Capital costs for wheat starch blasting systems
  vary depending upon the application. A PMB
  system for a small application can be modified for
  a cost of approximately $10,000: An automated,
  closed, dust-free system for a large application
  (e.g., aircraft) can cost up to $'1.5 million. The
  operating costs for wheat starch blasting systems
                                              46

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                                                                       Chapter 5: Surface Preparation
 Table 12.  Advantages and Disadvantages of Wheat Starch Blasting (TSSPO)
 Advantages
 Disadvantages
 4\'s biodegradable                 •'
 <»Can treat in a bioreactor
   Lowers waste volume to an estimated 5%
   of original volume
 * Can be used for removing coatings from both
   metallic and composite materials
 + Is easily controlled     .      - •
 * Can be used to selectively remove from one to
  • all coating layers   -   • •  .
 * Does not cause fatigue to the substrate surface
 4> Can achieve moderate stripping rates while
   maintaining a gentle stripping action
 * Is safe on'soft-ciad aluminum-
 * Has inexpensive .and non-toxic material
 * Eliminates water use
       ho size limitations on parts being stripped
 * Has high capital'invesfment cost  ""'
 + Requires complex subsystems for media
  recovery and recycling and dust collection
  and control    .                      ••_:.'
 ^Requires operator training  -   .
 *May result in a rough surface finish on delicate
  substrates if low levels of dense particle
  contamination exist
 *May require high disposal costs
 4 Typically slow to moderate stripping rate
 * Requires operators to wear personal   •
  protective equipment  .     .    '  •
       require an air dryer for humidity control
 have been estimated to be 50% less than those for
 chem ical paint stripping (such as methylene
 chloride)!

 Carbon dioxide
 Carbon dioxide (CO2) blasting is an alternative
^process to chem.ical cleaning and stripping. The
 obvious advantage of GO2 blasting over chemical
 stripping is the introduction of inert media that
 dissipates, in this case CO2. There are two basic
 types of CO, blasting systems: pellet blasting for   ,
 heavy cleaning and snow blasting for precision
 cleaning.- .    .  "                   ,

 CO2 Pellet Blasting       .

. CO, pellets are uniform in shape and the effec-
 tiveness of the pellets as a blast medium is similar
 to abrasive blasting. However, the pellets do not
 affect the substrate; therefore, CO2 pellet blasting
 is technically not an abrasive operation. This
 process can be used for cleaning, degreasing,.
 some de-painting applications,-surface preparation,
 and de-flashing (flashing is the excess material   .
 formed on the edges of molded parts).

' The process starts with liquid CO2 stored under
 pressure (-850 psig). The liquid CO, is fed to a
. pelletizer, which converts the liquid into solid CO2
 snow (dry ice flakes), and then compresses the
 dry ice flakes into.pellets at about -110°F. The
 pellets are metered into a compressed air stream
 and applied to a surface by manual or automated
 cleaning equipment with specially-designed
 Blasting nozzles. The CO2 pellets are projected
 onto the target surface at high speed. As the dry
 ice pellets strike the surface, they induce an
 extreme difference in temperature (thermal shock)
 between the coating or contaminant and the
 underlying substrate, weakening the chemical and
 physical bonds between the surface materials and ,
 f/ie substrate. Immediately after impact, the pellets
 begin to sublimate (i.e., vaporize directly from the
 solid phase to a gas), releasing CO2 gas at a high
 velocity along the surface to be cleaned'. The high
 velocity-is caused by the extreme difference in
 density between the gas and solid phases. This
 kinetic energy dislodges the contaminants (e.g.,
 . coating systems and flash), resulting in a clean
 surface. Variables that facilitate process optimiza-
 tion include the following: pellet density, mass
 flow, pellet velocity, and propellant stream tem-
 perature.

 C02.pellet blasting is effective in removing some •
 paints, sealants, carbon and corrosion deposits,
_ grease, oil, and adhesives, as well as solder and
 flux from printed circuit board assemblies-. Fur-
 thermore, because CO, pellet blasting is not an
 abrasive operation, it is excellent for components
 'with tight tolerances. This process also provides
 excellent surface preparation prior to application
 of coatings or adhesive and is suitable for most   .
                                              47

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Chapter 5: Surface Preparation
metals and some composite materials. However,
thin materials may be adversely affected. Blasting
efficiency is approximately equal to that of other
blasting operations. CO2 blasting can be done at
various velocities: subsonic, sonic, and even
supersonic. Therefore, equipment noise levels are
high (between 95 and 130 dB). This operation
always requires hearing protection.

Waste cleanup and disposal are minimized be-
cause only the coating or contaminated residue
remains after blasting. No liquid waste is created
because CO2 pellets sublimate to CO2 gas. They
pass from a liquid to a gaseous state, leaving no
spent media residue. With regard to air pollution
control, small quantities of coating particles are
emitted to the air. A standard air filtration system
should be utilized.

CO2 Snow Blasting
In contrast to CO2 pellet blasting, CO2 snow
blasting is a low impact process. This process
applies primarily to precision cleaning. A typical
precision cleaning operation must clean small
contaminant particles that, due to electrostatic
attraction, attach to surfaces and/or surface layers
of adsorbed moisture or soil. These particles are
so smalt that a large fraction of their surface area
attaches to the surface layers. CO2 snow blasting
 is mos.t effective in breaking the adhesive forces
and dislodging particles from the substrate surface.
 Small flakes of dry ice transfer their kinetic energy
to submicron particulate contaminants and then
 sublimate; lifting the particulate matter from the
 substrate surface as the adhesive bonds are
 broken. This process is often used as a final
 cleaning process for submicron particulate re-
 moval and light soils removal.

 CO, snow is generated from liquid CO2, and is
 discharged directly front the nozzle of the blasting
 device. The liquid CO2is partially vaporized as it
 passes through the nozzle, while the rest of the
 stream solidifies as pressure is reduced. The fine
 particles of "snow" are propelled by the fraction
 of CO, that vaporizes. No compressed air or other
 inert gas is needed to propel the snow.

 Many of the blasting media described in the
 previous sections cannot be used in precision
 cleaning because either they are too aggressive, or
they contaminate the component with media
residue. CO2 snow, however, is ideal for this
application because it is relatively gentle in appli-
cation, leaves no media residue, is highly purified,
and does not introduce new contaminants. CO2.
snow blasting is often done in a clean room or
cabinet purged with nitrogen to provide a dry
atmosphere, minimizing moisture buildup on the
component (TSSOP).

As a completely oxidized compound, CO2 is a
nonreactive gas, and thus is compatible with most
metals and nbnmetals. Dry ice processes are cold
and can cause thermal fracture of a component. In
addition, prolonged use in one spot will cause
condensation and ice buildup. However, this is
rarely a problem for CO2 blasting because it is a
fast-acting, nonstationary process. Particulate and
organic contamination is either quickly removed or
unable to be removed by continued blasting.
Therefore, the component temperature does not
change much, because contact time is short. •
Nevertheless, should component temperature drop
below the dew point of the surrounding atmo-
sphere, moisture will accumulate on the compo-
' nent. This problem can be mitigated by heating
the component in some manner so that its tem-
perature remains above the surrounding
 atmosphere's dew point after blasting. If compo-
 nents cannot take heat, then blasting can be done
 in an enclosed space purged with a dry gas to
 lower or eliminate the dew point problem
 (TSSOP).

 CO2 does not support combustion and it is
 nontoxic; however, it is an asphyxiant. CO2 will
 displace air because its density is greater than that
 of air, causing CO2 to accumulate at the lower  •
 level of enclosed spaces. When blasting with CO2
 pellets, additional ventilation should be provided
 for workers in enclosed spaces. Companies should
 also require use of personal protection equipment
 (PPE) when blasting (TSSOP).

 Static energy can.build up if grounding is not
 provided. CO2 blasting  should not be done in
 flammable or explosive atmospheres. High-
 pressure gases should be handled with great care.
 Companies should always chain or secure high-
 .pressure cylinders to a stationary support such as
 a column.
                                              48

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                                                                      Chapter 5: Surface Preparation
 CQ2 Pellet Blasting:

 1.   Units come in several different configura-
     tions.  •             •'  . •'     ',,-_''
 2.   The'blasting.unitcanbe purchased. Prices ;
   •' range from $25,000 to $50,000.
 3.   The blasting unit can also be rented.
   •  Monthly payments range from $ 1,500 to
     $2,500.        •
 ,4.   Units that combine pelletizing and blasting
     are also available, but generally are not'
     economical unless the blasting operation is
     performed 24 hours/day, 7 days/week.
 5.   Pellet blasting jobs can,be done on a
     contract basis for a cost between $200 to
     $300 per hour including labor, pellets,
     and equipment (not including travel time
     or'travel expenses).     '
 6.   A stand-alone pelletizer can be purchased
     for between $50,000 to $ 130,000
     (the cost to make pe.llets. from delivered
     liquid carbon dioxide is about $0.10 to
   •  0.15/lb),  '..

 "Purchased directly from a manufacturer for between
 $0.10 and $0.50/lb delivered, depending on the purify
 and the distance from the manufacturer (pelletizer
 purchase is reported to be economical only if blasting is
 done more than 40 hours/week). (TSPPO)
 CO2 Snow Blasting:

 Units'are much lower in cost and operation as'
 compared to CO2 pellet blasting, and again
 there are several different configurations to
 choose from:    .                =   >    '
 1 .•  All manual units'cost about $2,000.'
 2..  Semi-automated units, which can also be
     used in assembly applications, cost
   '  between $3,000 and $5,000.
 3.  For the highest quality of precision clean-
    sing with substantial volume requirements,
     CO2 purifiers are also available. Units .
     that can purify commercial grade liquid
   :. CO2 start at about $5,000. (TSPPO)   -.-
Sponge Blasting             •

Sponge blasting systems are a class of abrasive
blasting that uses (1) grit-impregnated foam and
(2) nonabrasive blasting media using foam without
grit. These systems incorporate various grades of
water-based urethane-foam cleaning media. Firms
use the nonabrasive media grades to clean delicate
substrates.. The abrasive media grades are used to
remove surface contaminants, paints, protective  •
coatings, and rust from a variety of surfaces. In
addition, the abrasive grades can be used to
roughen concrete and metallic surfaces. A variety
of grit types are used in abrasive media including
aluminum oxide, steel, plastic, or garnet (TSPPO).

The foam cleaning medium is absorptive and can"
be used either dry or wet with various cleaning
agents and surfactants to capture, absorb, and
remove a variety of surface contaminants such as
oils, greases, lead compounds, chemicals, and
radionuclides. The capability.of using the foam
cleaning medium in a!wet form provides for dust
control without excessive dampening of the
/surface being cleaned. The equipment consists of
three transportable modules, which include .the
feed unit,-the classifier unit, and the wash unit
(TSPPO).

The feed unit is pneumatically powered for.
propelling the foam cleaning medium. The unit is
portable and produced in several sizes. A hopper,
mounted at the top of the unit, holds the foam
medium. The medium is fed into a metering ,
chamber that mixes the foam cleaning medium
with compressed air. By varying the feed-unit  air
pressure and type of cleaning medium used,
sponge blasting can remove a range of coatings
• from soot on wallpaper to high-performance
protective coatings on,steel. and concrete surfaces -
(TSPPO). "'.'".

The classifier unit removes large debris and
powdery residues from the foam medium after
each use. The used medium is collected and
placed into an electrically-powered.sifter. The
vibrating sifter classifies the used medium with a
 stack of progressively finer screens. Coarse
contaminants, such as paint flakes and rust
• particles, are collected on the. coarse' screens.
 The reusable foam medium is collected on the
 corresponding screen size. The dust and finer
 particles fall through the sifter and are collected
 for disposal. After classifying, the reclaimed foam
 medium can be reused immediately in the feed
 unit. The abrasive medium can be recycled
 approximately six times and the nonabrasive  -
                                             49

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Chapter 5: Surface Preparation
Table 13. Advantages and Disadvantages of Carbon Dioxide Blasting
            (TSPPO)
Advantages
Disadvantages
* Significantly reduces the amount of hazardous
  waste and hazardous air emissions generated
  compared to chemical stripping.
*• Reduces the time required for cleaning/
  stripping processes  by 80 to 90%
*• Leaves no residue on the component surface
* Is effective in precision cleaning
* Introduces no new contaminants
* Is not always a one-pass operation; an effective
  blasting operation usually requires multiple
  passes to achieve the desired effect
* Requires operator training
* Can have high capital costs
* Can damage the components surface in
  fixed position blasting operations
•» Generates solid waste containing coating chips
  that are potentially hazardous; media does not
  add to the volume of solid waste
*• May carry coating debris that can contaminate
  workers and work area       ,
*Mdy redeposit some coating debris on substrate
* Can increase workers fatigue in non-automated
  systems because of cold temperature, weight/
  arid thrust of the blast nozzle
+ Can increase potential hazards from
  compressed air or high velocity CO2 pellets
 medium can be recycled approximately 12 times
 (TSPPO).

 During degreasing applications, the foam medium
 must be washed every 3 to 5 cycles. The washing
 of the foam medium takes place in the wash unit,
 which is a'po'rtable centrifuge, closed-cycle
 device. The contaminated wash water is collected,
 filtered, and reused within the wash unit
 (TSPPO).

 Thjs system removes paint, surface coatings, and
 surface'contaminants' from a variety of surfaces.
 Waste streams produced from this system include:
 coarse contaminants, such as paint flakes and rust
 particles; dust and finer particles; and the concen-
 trated residue from the bottom of the wash unit.,

 This technology helps prevent pollution for two
 reasons: the stripping media can be recycled (i.e.,
 every 10 to 15 events), and the quantity of
 wastewater that is typically generated using
 conventional methods (e.g., chemical stripping) is
 greatly reduced. -Sponge blasting systems are
 compatible in most situations where other types
 of blasting media have been used.
  As with any blasting operations, airborne dust is a
  safety and health concern. Proper precautions
  should be taken to ensure that inhalation of dust
  and particulate matter is avoided. Additional
  protective measures should be taken when
  stripping lead chromate- or zinc chromate-based
  paints, as these compounds may be hazardous.
  Inhalation of lead and zinc compounds can irritate
  the respiratory tract, and some compounds are
  known to be carcinogenic. Proper personal
  protective equipment should be used.

  High- and Medium-Pressure Water Stripping

  High- and medium-pressure water blast systems
  are used for paint stripping surfaces with low-
  volume water streams at pressures ranging from
  3,000 to 15,000 psi (medium-pressure opera-
  tions), and 15,001 to 55,000 psi (high-pressure.
  operations). These systems remove paint by
  spraying a stream of high-pressure water at the
  surface of the part. The advantages of this process
  include a readily available medium (water), an
  easily treatable waste stream, and an absence of
  fume and hazardous-waste production. A disad-  ,
  vantage of this process is the necessity for an
  automated system that usually uses robotics.
  Robotics is required for application due to the
                                             50

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                                                                      Chapter 5: Surface Preparation
  Table 14. Advantages and Disadvantages of Sponge Blasting Systems
               (TSPPO)
  Advantages
 Disadvantages
  * Is safer for operators compared to other':
    blasting media and chemi'cal stripper systems
  * Is1 easily transportable .. •• ,
  > Achieves waste minimization by recycling the'
    sponge media (i.e., can recycle sponge media
    an average of 10 to 15 times)
  * Absorbs and removes contaminants
  * Reduces dust generation
 «• Costs are more expensive than sand blasting
  media .     "                 '
 > Requires reasonably large capital investment
 extremely high pressure of the water stream
 (Freeman, p, 491).

 Medium-pressure systems may be augmented. For
 example, sodium.bicarbonate may be added to the
 water stream, or environmentally compliant
 chemicals may be applied to painted surfaces prior
 to water blasting. High-pressure systems typically
 use pure water streams. With both medium- and
 high-pressure water systems, specialized nozzles
 can be used to achieve varying effects. A rela-
 tively gentle, layer-by-layer process may be used
 for removal of organic paints versus the use of a
 different nozzle for the removal of metal flame
 spray coating and other tough, tightly adherent.
 coatings! The process water, paint, and residue are
 collected by an effluent-recovery system that.
 filters the paint and residue. The recovery system
 removes leached ions (e.g., copper, cadmium, and
 lead), microparticulates, chlorides, sulfates,
 nitrates, and other contaminants from the water.
 The water is then passed through a coalescing
 tank for removal of oils and film, then through
 charcoal filters, microfilters, and finally, a deion-
 ization system to ensure that the water is Grade A
 deionized water. The recovered deionized water is
 recycled back into the process (TSSOP).

• No material compatibility problems have been
 documented for use of high- and medium-pressure
 water processes to de-paint metallic surfaces. The
. use of specific chemicals to augment medium-
 pressure water processes must be evaluated on a
 case-by-case basis. The automotive industry
 .currently uses high-pressure water jets to remove
  paint from the floor of painting booths
  (IHWRICf).          .            .  .,-•
 The capital costs for high- and medium-pressure
 water processes vary considerably depending on  •
 the process and its application. Capital costs for
 medium-pressure systems range from $40,000 to
 $70,000, and capital costs for high-pressure  •
"systems range from $850;QOO to $1,500,000.

 Fluidized Bed Stripping              .

 The fluidized bed paint removal process is an
 alternative method to chemical paint stripping and
 degreasing of nonaluminum and nonheat sensitive
 metal parts. In fluidized bed stripping, an air
 stream is pumped into a tank of quartz sand or
 aluminum oxide, making it a fluid. Natural gas is
 mixed with the air and ignited above the tank,
 creating temperatures of approximately 800°F.
 Objects to be stripped are lowered in a basket into
 the tank. The paint is vaporized, and the gases
 and unburned natural gas are burned in a
 postcombustion chamber above the^ank. A wet
 scrubber removes the solids from the final exhaust
 before it is vented into the air. The;most notable
 advantage of this process is that it produces no
 solvent wastes. This method works for steel parts
 but not for aluminum parts (IHWRICf). Technical
 assistance providers should not recommend the
 fluidized bed paint stripping (FBPS) process for
 use with aluminum and aluminum alloy parts
 because these materials lose essentially all of their
 hardness or temper when exposed to the 700 to
, 800°F process temperatures (TSSOP).

 The FBPS process typically consists of the
 following four components: 1) fluidized bed
 furnace'or retort, 2) fluidized bed cooling system,
 3 ) off-gas treatment system cons isting of a
 cyclone, afterburner and :scrubber, and 4) low
                                              51

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Chapter 5: Surface Preparation
 Table 15.  Advantages and Disadvantages of a Water Blasting System
              (TSPPO)
 Advantages
    Disadvantages
  4- Reduces hazardous.waste by 90%
  * Selectively removes individual coating layers
  *• Does not need pre-washing, and masking is not'
    needed in most applications
  * Are no size limitations for parts being stripped
  * Generates wastewater stream  that is compatible
    with conventional industrial wastewater plants
    located at many installations
  * Has low implementation cost utilizing simple
    robust equipment
  * Reduces the process material costs significantly
  «• Reduces labor hours for the stripping process
    by 50%
  4 Generates no dust or airborne contaminants
  * Requires-no cleanup after stripping
    * Has high capital costs
    * Removes one layer at a time
    •+ May not remove corrosion
    * Must consider the substrates to be, removed
      for impact on personal protection and
      waste collection/disposal
    * Generates a potential hazardous
      waste  stream
    * Requires review of wastewater disposal
      requirements for toxicity of the coating
      being removed
    * Must protect employees from direct
      impingement of water jet
    * Requires operator training
    *Can damage joints, seals, and bonded
      areas &y. water penetration
    ^-Requires additives to the water that may
      have an adverse effect (i.e., flash rusting) on
      the surfaces being cleaned
    •*• Has variable stripping rates from differ-
      ences in type of paint, coating condition and
      coating thickness
 energy shot-blast unit. The fluidized bed furnace
 or hot bed is where pyrolysis of the coatings takes
 place. A granular material, aluminum oxide
 (alumina) in most cases, is used as a heat-transfer
 medium. Air passing through the bed keeps the.
 medium fluidized. Parts to be cleaned are lowered
 into the fluidized bed, which quickly heats the part
 and its surface coatings (e.g., paint, grease,  and
 oil) to a temperature at which organic components
 of the surface material pyrolyze into carbon.
 oxides, other gaseous combustion products, and
 char. The fluidized bed  cooling system, or cold
 bed, is used to cool the  parts after the organics
 have been pyrolyzed. Carbon monoxide and
 volatiie organic compounds (VOCs) generated
 during pyrolysis are burned in the afterburner. The
 thermal decomposition of paint leaves some
 carbon and inorganic char on the part. Most of the
 char may be removed in the fluidiz'ed bed; how-
 ever, most parts require further cleaning before
 they can be repainted. The shot-blast unit is used
 to remove the inorganic coatings and char to
 prepare the parts forrepain.ting (TSSOP).
This process removes and destroys paint and
grease from nonaluminum or nonheat sensitive
materials. Waste streams from this process include
spent heat-transfer medium, spent blast media,
exhaust air from the afterburner and scrubber,
water discharge from the scrubber, and dust from
the cyclone separator. The heat-transfer medium,
. blast media, and.cyclone dust contain metals from
the stripped paint.               ..    .

Assistance providers should also inform facilities
that this blasting method requires employees to
wear equipment to protect them from toxics in the
paint. For example, inhalation of lead and zinc
chromate paints can lead to irritation of the
respiratory tract; some lead compounds are
carcinogenic; solvent-based'paints-can irritate the
 lungs and mucous membranes; and prolonged
• exposure can affect respiration and the central
 nervous system.
                                             52

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                                                                     Chapter 5: Surface Preparation
 Costs for fluidized bed paint strippers can range
 from $7,000 for a small parts stripper to $800,000
 for ah industrial scale stripper.   ..'.-.

 Other  Methods

 The methods that follow can also be used to strip
 old paints from metal parts.        .        •   ,

 High-energy Light. High-energy light uses-
 optically directed beams of photon energy emitted
 by lasers or flash lamps (typically xenon lamps) to
 ablate the paint. Using high-energy light to remove
 paint decreases operating cost, minimizes the
 waste stream, and lowers the possibility of
 material damage. The disadvantages of this
 process are its high capital cost and precision
 robotics requirements (Freeman, p. 490)

 Cryogenic  Methods. Cryogenic methods
 generally use liquid nitrogen immersion at approxi-
 mately r200°F, which causes the paint to contract,
 breaking the adhesive bond with the substrate. For
 small components, a tumbler design normally is
 used, where the parts can impact and abrade each
 other to assist in removing the paint. If the parts
 have complex shapes, tumbling media might be
 added (Freeman, p. 491). Cryogenic stripping has
 a harder time removing epoxy and urethanei
 coatings than other coatings.  Also, this stripping
 method removes thick coatings more efficiently
 than thin coatings. In addition, this method may
^ damage or distort parts because of the extreme
 temperatures needed in the process (IHWIRCf).
 High-temperature Thermal  Methods.
 High-temperature thermal methods, such as
 burnoffovens and molten salt baths, are some-
 times used to strip paint. In general, these meth-
 ods are labor intensive, and result in emissions of
 burned paint and metal surfaces that are fouled^
 by heat scale. This heat scale, subsequently, must
 be removed by abrasive methods,.such as
 sanding or wire brushing. Most thermal methods
 are limited to heavy metal parts that will not warp
 because of thermal expansion and distortion
 (Freeman, p. 490). In burnoff ovens, the ovens
 simply burn off the paints. This method is limited
 to steel parts (IHWRiCf).

 Molten salt baths remove paint easily from metal.
 Baths that are only 500 to 700°F significantly
 reduce any problems with heat distortion. Objects
 to be stripped are lowered into the salt bath",
 removed, rinsed with water, lowered in dilute acid,
 and immersed in water agajn. Care must be taken
 in stripping aluminum parts; leaving the parts in
 the bath for more than 60 seconds could, soften
 the metal and make the parts unusable. Also, salt
 can solidify or get trapped in an area that cannot
 be thoroughly rinsed, causing corrosion at a later
 time(IHWRICf).

 Burnoff ovens and molten salt baths often are
» used to remove paint overspray from hooks,
 racks, grates, and body carriers used in automo-
 tive plants. Stripped parts are left with a residue of
 ash, which can be removed by rinsing (Freeman,
 p. 491).                          ..'--./
   Table 16. Advantages and Disadvantages of Fluidized Bed Stripping (TSPPQ)
   Advantages
Disadvantages
   ,•* Leaves practically no waste.paint residue,
     thus eliminating significant waste sludge
     disposal costs.as well as avoiding the future
     liability associated with the hazardous
     components of the'paint sludge
   + Uses an inert medium to clean parts of any
     shape, size, or geometry which are coated
     with any type of paint; the rapid changes in
     coating technology do not affect the
    ' performance of the system
   * Provides cleaning  to the bare metal
O Is not suitable for removal of paint from
  aluminum and aluminum alloy parts
* Is not suitable for parts with crevices, channels,
  or cavities (e.g. engine blocks) that would
  retain FBPS media and be difficult to clean
  after treatment
«• Has little or no effect on corrosion'removal
•»May require secondary cleaning to remove
  char and inorganic coatings from parts
«• May generate more waste than a caustic •
  stripping system
                                              53

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   Chapter 5: Surface Preparation
Table 17. Overview of Alternative Surface Preparation Technologies (EPAh, p. 7-
          10, EPAi, p. 5-6, 24, EPAg, p. 7-9 and IHWRICf)
;•






































Technology
Cleaning
Aqueous
Cleaning





•
'
Ultrasonic
Cleaning




Supercritical
Fluids

<

Vacuum
De-oiling













Laser Ablation

'ollution
Prevention
Benefits >

Reported
Application

Operational
Benefits


Limitations

* Eliminates solvent
•use by using
water-based
cleaners






+ Eliminates solvent
use by making
aqueous cleaners
more effective


4>Nonpollutingwhen
CO2 is used as the
supercritical fluid .

•
* Eliminates solvent
use for cleaning













* Eliminates solvent
use for cleaning
» Used to remove
light oils and
residues left by
other cleaning
processes
* Used to remove
heavy oils, greases,
and waxes at
elevated temp-
eratures
* Cleaning of ceramic,
aluminum, plastic
and metal parts,
electronics, glass-
ware, wire, cable
and rods
* Precision cleaning
. of stainless steel,
copper, silver,
porous metals, and
silica
* Removal of oils
from metals













* Cleans metallic or
nonmetallic surfaces
^Cleaning
performance
changes with
concentration and
temperature, so
process can be
tailored to
individual need
+ Cavitate Using
ultrasonics
*Can clean in small
crevices '




* No solvent residue
left on parts
* Low operating
costs

* Low operating costs
+ Does not leave the
cleaned parts water-
soaked, therefore
parts do not need to
be dried










* Localized cleaning

* May generate
significant amounts
of hazardous
wastewater
*Some acids can
cause hydrogen
embrittlement . .




•




* High capital cost



* Parts must be"
able to withstand'
the required
' . temperature and.
vacuum pressure
VHigh capital costs
* Adjustments might
be needed for
each application
because the time
and temperature of
the de-oiling
process depends
on the material to
• be, cleaned and the
oil to be removed
'
' ' 1
(continued on next page}
                                        54

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                                                          Chapter 5: Surface Preparation
Table 17. Overview of Alternative Surface Preparation Technologies (EPAh, p.
           7-10, EPAi, p. 5-6, 24, EPAg, p. 7-9 and IHWRICf) '(continued)
Technology
Pollution
Prevention
Benefits
Reported
Application
/
Operational
Benefits
Limitations
Stripping
Abrasive
Blasting
High-energy
Light
, ^Lasers
+Flash lamps
Cryogenic
Stripping
High-pressure
Water
Thermal
Stripping
•* Fluidized bed
stripping
* Molten salt
baths
* Burnoff ovens
* Eliminates solvent,
use in stripping
* Eliminates solvent
use in stripping
* Eliminates solvent
use in stripping
* Eliminates solvent
use in stripping
+ Water can be
processed and
recycled during
stripping, reducing
wastewater volume
+ Eliminates solvent .
use in stripping


* Removes thick
coatings from
a variety of .
coating line
fixtures and tools

•'* Fluidized- bed
stripping and
molten salt baths
, can be used only
on steel parts .
* Blast substitutes
available: plastic
media, sodium bi-
carbonate, carbon
dioxide, and wheat
starch
+ Lovv chance of "
material damage

*High stripping rate
/ " '
*Can process
complex shapes
* Harder materials
can damage
metals
= f
* High capital costs
^•Precision robotics
required
* Does. not remove
epoxy or urethane
coats as well as
other types.
* Does not remove
thin coats as well
as thick ones
* Extreme tempera-
tures can damage
or distort parts
* Misapplied water
jet may damage ,
substrate
* Blasting generates •
high noise levels
* Water can enter
cavities penetrat-
ing and/or
damaging joints,
seals, and bonds
* Fluidized bed-'
stripping cannot .
be used on
aluminum
                                     55

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Chapter 5: Surface Preparation
                                                     56

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6
Alternatives  to
Solvent-Borne  Coatings
        The majority of conventional coatings are
        solvent borne, traditionally containing about
      25% solids and a relatively high organic solvent
      content. These materials generally have been
      applied with conventional air spray, which uses
      compressed air at high pressures to atomize paint,
      a technique known as low-volume/high-pressure
      (LVHP). LVHP and other application techniques
      are discussed in chapter 7. This chapter covers the
      composition of conventional metal coatings, low-
      to-no solvent alternatives, and lower toxicity
      alternatives. The US EPA's Coatings Alternative
      Guide (CAGE) (available via the Internet at http://
      cage.rti.ofg) is a helpful tool for assistance provid-
      ers to use in identifying specific alternative
      coatings for facilities.

      Conventional Paint

      Composition

      The major components of paints and coatings are
      solvents, binders, pigments, and additives. In
      paint, the combination of the binder and solvent is
      referred to as the paint"vehicle." Pigment and
      additives are dispersed within the vehicle
      (IHWRIC, p. 2). The amount of each constituent
      varies with the particular paint, but solvents
      traditionally make up about 60% of the total
      formulation. Binders account for 30%, pigments
      for 7 to 8%, and additives for 2 to 3% (KSBEAP,
      p. 4).         •'_:.

      '^•Solvents are added to coatings to disperse
        the other constituents of the formulation and to
        reduce viscosity, thereby enabling application
        of the  coating. A wide variety of solvents are
        used in paints, including aliphatic hydrocar-
        bons,  aromatic hydrocarbons (toluene, xylene,
        and the tri methyl benzenes), ketones (methyl
        ethyl ketone (MEK) and methyl isobutyl ketone
        (MIBK)), alcohols, esters, and glycol ethers
     ''..  {IHWRIC, p. 5).
                                        A Few Words About Solvents

                                        A solvent is typically selected based on its
                                        ability to dissolve binder components
                                        (resins), and its evaporation rate. Its ability to
                                        dissolve binder components is often referred
                                        to as solvent power. Combinations of  -.
                                        different solvents are often found in paint
                                        formulations. The most widely used solvents :
                                        are toluene, xylene, MEK and MIBK.

                                        * Toluene will dissolve a large number of
                                          resins. Toluene is miscible with drying oils
                                          like linseed oil or king oil that are often
                                          used in oil-based paints and with most
                                          other solvents.

                                        *Xy/ene has high solvent power with a
                                          wide range of resins'and a high rate of
                                          evaporation. As a result, xylene is widely
                                          used in both heat-cured and rapid air-
                                          drying coatings.

                                        > MEK. and MIBK are solvents used with a
                                          wide range of resins. MIBK is extensively
                                          used in both heat-cured enamels and
                                          lacquers (EPA, p. 154-155).
                                       Solvents are a major source of environmental
                                       concern because at normal temperatures and
                                       pressures they, can volatilize (i.e., the liquid
                                       solvent becomes a vapor). Exposure to these
                                       solvent vapors is dangerous for a number of
                                       reasons. In the workplace, solvent vapors can
                                       result in a number of human health risks. Table 18
                                       presents information on the health effects of
                                       solvents used in paint formulations. Solvent
                                       vapors also can pose fire/explosion hazards,
                                       necessitating careful storage and handling proce-
                                      . dures.    ;

                                       When solvent vapors arereleased, they emit
                                       volatile organic compounds (VOCs) and hazard-
                                               57

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Chapter 6: Alternatives to Solvent-Borne Coatings
     Table 18.  Health  Effects of Solvents Used in Paint Formulations0 (EPAe)
     Solvents Used
     in Paint
     Formulations
Health Effects
     Toluene
 •The central nervous system (CNS) is the primary target organ for toluene toxicity in both
  humans and animals for acute (short-term) and chronic (long-term) exposures.  CNS
  'dysfunction (which is often reversible) and narcosis have been frequently observed in
  humans acutely exposed to low or moderate levels of toluene by inhalation; symptoms
  include fatigue, sleepiness, headaches and  nausea.  Cardiac arrhythmia has also been
  reported in humans acutely exposed to toluene.
 >CNS depression has been reported to occur in. people chronically exposed'to high levels of
  toluene. Symptoms include ataxia; tremors; cerebral atrophy; nystagmus (involuntary eye
  movements); and impaired speech, hearing and vision. Chronic inhalation exposure of
  humans to toluene also causes irritation of the upper respiratory tract, eye irritation, sore
  throat, nausea, skin conditions, dizziness, headache and difficulty with sleep.
 > None of the available data suggest that toluene is carcinogenic. Two epidemiological
  studies did not detect a statistically significant increased risk of cancer due to inhalation .
  exposure to toluene. However, these studies had many confounding factors. Animal studies
  have also been negative for carcinogenicity. EPA has classified toluene as not classifiable
  as to human carcinogenicity.
     Xylene
* Acute (short-term) exposure to mixed xylenes in humans results in irritation of the nose and
  throat; gastrointestinal effects such as nausea, vomiting, and gastric irritation; mild
  transient eye irritation; and neurological effects.
* Chronic (long-term) inhalation exposure of humans to mixed xylenes results primarily in
  central nervous system (CNS) effects, such as headache, dizziness, fatigue, tremors and
  incoordination. Other effects noted include labored breathing and impaired pulmonary
  function, increased heart palpitation, severe chest pain and an abnormal EKG, and
  possible" effects on the blood and kidney.
 > Insufficient data are available on the developmental or reproductive effects of mixed
  xylenes on humans. Animal studies have reported developmental effects such as an
  increased incidence of skeletal variations in fetuses and fetal resorptions via inhalation.
 >No information is available on the carcinogenic effects of mixed xylenes in  humans, and
  animal studies have reported negative results from exposure through gavage (experimen-
  tally placing the chemical  in the stomach). EPA has classified mixed xylenes as  not      •
   classifiable as to human carcinogenicity.                               .      .
      Methyl  Ethyl
      Ketone
 * Acute (short-term) exposure to methyl ethylketone in humans, via inhalation, results,in.
   irritation to the eyes, nose and throat; and, central nervous system depression.
   No information is available on the developmental or reproductive effects of methyl ethyl
   ketone in humans. Reduction of fetal development and fetal malformations has been
   reported in mice exposed to methyl ethyl ketone in the air.
   Limited data are available on the carcinogenic effects of methyl ethyl ketone. No human
   data are available and the only available animal study did not report skin tumors from
   dermal exposure to methyl ethyl.ketone. EPA has classified methyl ethyl ketone as not
   classifiable as to human-carcinogenicity.  .
      •These solvents are nonha/ogenated hydrocarbons; that is, they do not contain chlorine or related elements. Nonhalogenated hydrocarbon
      solvents are often used in paint formulations as well as in surface preparation and equipment cleaning. Ha/ogenated hydrocarbons are hydrocar-
      bon solvents that contain one or more of the halogens (i.e., fluorine, chlorine, bromine, iodine and astatine). Examples include tnchloroetnylene
      (TCE), perchloroethylene (PERQ, 1,1, Hrichloroethane (TCA), carbon tetrachloride, methylene chloride (METH) and CFC-1 13. The halogenqted
      hydrocarbon solvents are preferred foryapordegreasing operations because their flashpoints are in a higher range than those of the.
      nonhalogenated solvents; therefore, they are usually not ignitable. However, halogenated solvents, in general, are more toxic to humans and
      capable of causing greater environmental damage (IWRC, p. 13-14). •                       •              .         '

                                                          58

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                                                                  Chapter 6: Alternatives to Solvent-Borne Coatings
 ous air pollutants (HAPs) into the atmosphere.
 VOCs combine with nitrogen oxides in the pres-
 ence'of sunlight to form ground-level ozone.
 Ground-level ozone is a precursor to smog, a
 major pollutant in urban and industrial areas.
 Smog poses a number of human health risks to
 respiratory function, particularly among persons
 with asthma or allergies.

 + Binders are liquid polymeric or resinous
   materials that are used in coatings to hold the
   pigment and additives together, to provide
   adhesion, and to enable the coating to cure
   into a thin plastic film, The binder provides the
   working properties of the'coating and deter-
   mines the performance of the film, including
   flexibility, durability and chemical resistance
  • (EPA,  p. 152-154). Most binders are named
   for their main resin. The resins most commonly
   used  in paints and coatings are natural oils or
   vegetable oils, alkyds, polyesters, arhinoplasts,
   phenolics, polyurethanes, epqxies, silicones,
   acrylics, vinyls, cellulpsics and fluorocarbons
   (SME, p. 26-3-4). See "A Few Words About
   Binders" for more, information.
                                           A '
 V Pigments are insoluble  particles of  organic
   or inorganic materials (either natural or
   synthetic) that are dispersed in  a C9ating in
   order to confer  color and opacity to a sub-
   strate, or to improve the substrate's envirph-
   '.mental  resistance and the flow properties of
   the paint. The type  of pigment in the paint
 .  . determines the color and color stability of the
    paint or coating, while the amount  of pig-
    ment determines the gloss,  hiding power and
    permeability of  the coating  (EPA, p. 1.52-.
    1 54). Inorganic pigments have high thermal
    stability and ultraviolet  light stability. Organic
  •  pigments are ^brighter and clearer than
    inorganic pigments (KSBEAP, p. 5).

  Many pigments still contain lead, chromium,
  cadmium, or other heavy metals. These paints
  cannot be disposed of in a landfill and must be  •
  handled as a hazardous waste because the heavy
  metals can leach out of latidfills and contaminate
'  groundwater. Production of paints containing
  these heavy metals is being phased out due to
  their toxicity (KSBEAP, p.5). EPA banned the
  production of certain paints containing lead and
 A few Words About Pigments

 The four commonly recognized classes of   . •
 pigments are:"colored pigments; white
 pigments, which include the primary and  .
 extender pjgments; metallic pigments; and
 functional pigments, which provide corrosion
 resistance, antifouling protection, slip  .
 resistance or other desired properties.
 Colored pigments are available in both
 inorganic and organic compounds (SME, p.
 26-9). Inorganic pigments have high thermal
 stability and ultraviolet (UV) light stability.
 Organic pigments are brighter and clearer
 than inorganic pigments (KSBEAP, p: 5).
 Examples of each type follow: .

 '4 Colored pigments: red/yellow/black iron
    oxide, blue/green phtalocyanine and
    gilsonite
 «• White pigments: lithopone and titanium
   '. dioxide                  •
 > Metallic pigments: yemniculite (texture),
    flake aluminum (sparkle/metallic appear-
 ..   ance), and titqnid and surface-modified  •
    talc (pearlescence)
 > Functional pigments: limestone and clay
    (fillers); barium metaborate (preservatives
    against mold, mildew or bacteria);
    lithopone and zinc sulfide (UV stabilizers);
    nickel/copper/silver powders and barium
    titanate (conductive ability); and carbon
    black, silica, Attapulgus clay and fibers
    (reinforcement) (Athey, p. .59)
mercury several years ago. However, some-
facilities may still have these paints in use if they
purchased the paints prior to the phaseout..

* Additives are materials that improve the
  physical and chemical properties of the
  coating; Additives include surfactants, colloids
  and thickeners, biocides and fungicides,
  freeze/thaw stabilizers, coalescing agents,
  defoamers, plqsticizers, flattening ag«nts, flow
  modifiers, stabilizers, catalysts and antiskinnihg
  agents (SME/p. 26-13). A coating's character-
  istics can change significantly depending on .
  which-additives are included.    •
                                               59

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Chapter 6: Alternatives to Solvent-Borne Coatings
      A Few Words About Binders

      Binders are chosen based on what physical and chemical properties are desired of the finished film. In
      general, metal coatings are dominated by alkyds; however, water-based acrylics, epoxies, polyure-
      thanes and polyesters also are used for certain applications (MPCa, p. 34).

      4Acry//cs and alkyds contain suspended polymer particles. These materials produce a shiny, hard
        finish that has good weather resistance. Alkyds are made from chemically modified vegetable oils
        and are relatively low in cost. They are easily modified in order to change the properties of a paint.
        They also can react with other chemicals in the curing process to change the finish. In ambient
        conditions, they react with oxygen to form cross-linked films, making them functional for a wide
        variety of applications. Because of the versatility and moderate cost, they are considered "general
        purpose paint" (KSBEAP, p.4). Both acrylics and  alkyds are widely used for farm equipment and
        industrial products that require good corrosion protection at a moderate .cost. Silicone modification
        of these resins improves overall weatherability and durability. These finishes are often used on space
        heaters, clothes dryers and barbecue grills.

      4 Urethanes combine high gloss and flexibility with chemical and stain resistance.  They are also
        characterized by toughness, durability and corrosion resistance. They require  little or no heat to cure.,
        These materials usually cost 2 to 5 times more than other paints so they are often used in applications
        where high performance justifies the cost (KSBEAP, p.4). Typical uses are on conveyor equipment,
         pircraft radome's, tugboats, road-building machinery and motorcycle parts.

         Urethanes are produced by a reaction between  isocyanate  and alcohol. The components can be
         mixed in a "pot" priorto application or can be mixed in the atomizing portion of the spray gun.
         Once mixed, urethanes have a limited "pot life," which is the amount of time the components can be
         mixed before crosslinking occurs. Often, pot life can be adjusted to meet process requirements;
         typical ranges available commercially are a few minutes to 16 hours (KSBEAP, p.5).

       4 Epoxies provide excellent water and chemical resistance. They have better adhesion to metal
         substrates than most other materials. Epoxies are attractive  economically because they are  more
         effective'against corrosion in thinner films than most other finishing materials.  They are often used
         as primers under  other materials that have good  barrier properties but marginal adhesive charac-
         teristics. They can be formulated in a variety of ways, from one-component formulations requiring
         elevated temperature curing to two-component systems that cure at or below  ambient tempera-
         ture conditions. Epoxies lose their gloss from ultraviolet exposure but the damage is rarely struc-
         tural (KSBEAP, p.4).

       ^Polyesters, are similar to alkyds in chemical structure but require heat to cure. They are used exten-
         sively in powder coatings. Polyesters, such as Nylon 11, provide an attractive appearance as well as
         protection from chemicals, abrasion and impact. Nylon coatings are used on office and outdoor
         furniture, hospital beds, bending machine parts and building railings. Heavier coats can be used to
         protect dishwasher baskets, food-processing machinery, farm and material-handling equipment, and
         industrial equipment such as pipes/fittings and valves (MD, p. 703-704).

      ' + Ofher Binders, such as silicones have high heat resistance and superior resistance to. weather and
         water. They are used alone or blended with acrylics or alkyds. Vinyls are another binder that can
         have a wide range of flexibility. They are used extensively in marine applications, interior metal can
         liners (e.g., polyvinylchloride), or structural wood finishes (e.g., polyvinylacetgte) (KSBEAP,  p.5).
                                                    60

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                                                                 Chapter 6: Alternatives to Solvent-Bome.Coatings
 Switch  to  Surface-

 Free  Coating

 Many manufacturers are finding that they can
 eliminate unnecessary paints and coatings that are.
 used only for appearance. Ijfotpnly does this
 reduce capital, operating and maintenance costs, it
 also reduces potential liability from toxic chemical
 use (EPA, p. 1-59). The use of injection-molded
. plastic sheets in place of painted metal cabinets in
 the electronics industry is one example of this
 trend (Freeman, p. 485). Manufacturers that are
• considering product redesign to eliminate unneces-
 sary coatings must consider the substrate  and its
 characteristics without a coating. If the coating is
 needed to provide an engineering function, such as
 improved corrosion resistance, one option may be
 to change to a base material that does not require
 a coating (EPA, p. 160). Currently available
 materials that are free of surface coats include
 plastics, aluminum, titanium and other .metals.  \
 Other materials that are under development for a
 wide range of industries include: cement-bonded
 particle boards, pultruded products from fiber-
 glass-reinforced plastic, uncoated metals, weath-
   CA5E STUDY:
   Chrysler Corporation

   The Chrysler Corporation's manufacturing-
   plant in Belvidere, Illinois, ho longer needs  -
   to apply zinc-rich primers to car bodies:
   Chrysler now uses galvanized metal (zinc-
   plated) instead,* a move that has saved the
   company $7,000 per year and eliminated
   nearly 1 50 gallons of waste paint. Chrysler
   also has begun to use more waterborne
   paints in its production lines.

   ^Savings
      Chrysler estimates that its pollution preven-
      tion efforts so far have saved the company
      $350,000,

      *Althbugh substituting galvanized metal might
      reduce the amount of VOGs generated, a lifecycle
      analysis could reveal that zinc plating produces a
      number of other wastes. If a company chooses to
      purchase galvanized metals from outside firms,:they
      could simply be passing along a different pollution
      burden to their supplier rather than achieving
      pollution prevention.  '           .' (IHWRICd)
 ering steel and polymer film coatings (TORI, p.
 2>-'. '•'      "      :'    -   ;     .
 Alternative Coatings

 The primary advantage of conventional solvent-
 borne paints is their versatility.  However, due to
 the low solids content of conventional solvent-
 borne paints, a high volume of paint is required to
 supply a small amount of coverage. In addition,  ,
 because the paint solvent is highly atomized along
 with the paint solids in LVHP application, VOC
 emissions are high (MnTAP, p. 3-4), See figure 3 .
 for more information.

 Vendors have developed a number of alternative •
 coating technologies. Environmental compliance
 remains the principal driver for the development
 of new technologies (Tilton). These new technolo-
 gies include:

 * High-solids coatings  -               .
 > Waterborne coatings   ;      '             . •
. •* Powder coatings
 + Radiation-cured coatings        '.   .
 > Emerging technologies such as vapor perme-
  ' atioh of injection coatings and supercritical
    carbon dioxide

 These^coating alternatives can reduce emissions of
 VOCs and, in so doing,- reduce the generation of
 hazardous  wastes and decrease worker exposure
 to toxic air emissions (EPAd, p. 1-5). Each of the
 alternatives is discussed on the following pages.
  Generally, the P2 alternatives are not one-to-one
  substitutions. In some cases, an alternative
  requires a process change using a specific applica-
  tion and/or curing method (e.g., powder coating).
  Alternatives also can raise other issues (e.g., less
  solvent in the coating generally requires more
  thorough surface preparation). For an overview of
  alternatives to solvent-borne coatings, see table
  19. Firms should consult with coatings suppliers
  for more detailed information on product -offer-
  ings, as a number of hybrid technologies and
  different chemistries have recently been intro-   '
  duced (Tilton).

   The relationship between emissions and VOG
  content, though obviously direct, is not linear; in
  other words, the transfer efficiency of the applica-
  tion method also can have a significant impact on
                                               61

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Chapter 6: Alternatives to Solvent-Borne Coatings
       Figure 3. Emissions versus VOC Content (EPA-450/2-77/008)
                                                              Solvent content
                                                              of original
                                                              coating (Ibs/gal)
                                     12      3      4      5   •
                                         Pounds of solvent per gallon
                                     of replacement coatings (less water)
                                        solvent density =  7.36 Ibs/gal
        the amount of VOCs emitted. This issue is
        explored in chapter 7 (Falcone, p. 35).


        High-Solids Coatings


        General  Description

        High-solids coatings have a higher percentage of
        paint solids and a lower percentage of solvent
        carriers than conventional solvent-borne coatings
        (MnTAP, p. 4). EPA defines high-solids paints as
        systems with volatile organic contents of less than
        2.8 pounds per gallon. Paints with more than 85%
        solids content by weight are also generally referred
        to in the coatings industry as high-solids paints. In
        practice, paints with a solids content of 60 to 80%
        can be called high-solids paints per EPA's defini-
        tion, especially if the equivalent solvent-borne  •
        paint contains more than 50% solvent (EPA, p.
        162).
modified so that it has a much lower intrinsic
viscosity than binders of conventional solvent-
borne paints. To overcome performance limita-
tions, additives often are used to increase
crosslinking during curing (EPAd, p. 15). The
binders in high-solids paints include alkyd resins,
polyester resins, polyurethanes, acrylic resins,
epoxy resins and poly vinyl chloride plastisols.
Nondrying alkyd resins crosslinked with melamine
during heat curing are often used for industrial
coatings (EPA, p. 162-163).'

Advantages  and  Disadvantages

Because high-solids coatings contain less solvent
than traditional formulations, VOC and HAP
emissions are reduced in this process (e.g., up to
50%, in some cases) (VT DEC). High-solids
paints also provide higher layer thicknesses per
application cycle than conventional coatings,
resulting in a savings in time. Despite past issues
• with viscosity, today's high-solids paints can be
 applied with conventional spray equipment (EPA,
 p. 162-163). However, surface preparation of the
 substrate remains a critical issue. This is because a
        To achieve solids contents exceeding 70%, the
        binder in a high-solids paint must be chemically
        1 For more information see, "High So/ids, Low VOC, So/venf-hased Coatings," by Ron Joseph; part of the Metal Finishing
        Special: Organics Finishing Guidebook and Directory that provides detailed information on the advantages/disadvan-
        tages of specific resin types.                                     •
                                                    62                  '            :

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                                                      Chapter 6: Alternatives to Solvent-Borne Coatings
Table 19.  Overview of Alternatives to Solvent-Borne Coatings (EPAd, p. 12
           andKSBEAP, p. 12)


Technology
High-Solids"








Waterborne

^ ' '












\ ' i




L -. - ,

Pollution
Prevention
Benefits
* Reduces solvent
in coatings (low
- voq,_ .
* Has less over-
spray compared
to conventional
coatings
'-. ' ' . . •

>Eiiminatesor
reduces solvent
in coating (little
ornoVOC)
> Uses water for
cleanup






.









. ' -. .
Reported
Application
* Zinc-coated
steel doors "
*• Miscellaneous
metal parts
+ Same as
conventional
coatings
•i .

4 Wide range
4 Architectural
trade finishes,
* Wood furniture
* Damp concrete
' e

















Operational
Benefits
*Gan apply thick
orthin'coat
* Has easy color
blending or
changing
4 Is compatible
with conventiona
and electrostatic
equipment
* Can apply thick
orthin'coat
* Has«asy color
blending or
changing
* Is compatible
with conventional
and electrostatic
application
equipment








>
- •




Limitations
* Does not eliminate
solvent completely
+ Has shorter pot life
than conventional
coatings • -
4 Must be heated
v ' '

•. ' • •
4 Has coating flow
properties and drying
rates that can change
With humidity, affect-
ing coating
application
* Is sensitive to humidity;
workplace humidity
control required
4 May have poor flow
characteristics 'due to
high surface tension of
water
* Needs special equip-
ment for electrostatic
application
4 Has water in paint that
can cause corrosion of
storage tanks and ,
- transfer piping, and
"flash rusting" of metal
' substrates
                                                              (continued on next ptige)
                                     63

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Chapter 6: Alternatives to Solvent-Borne Coatings
       Table 19. Overview of Alternatives to Solvent-Borne Coatings (EPAd, p. 12
                    and KSBEAP, p. 12) (continued)


Technology
Powder














Radiation-
cured





•


Pollution
Prevention
Benefits
^•Eliminates solvent
in coating (no.
VOC) in most
cases
^Reduces solvent
in cleanup
^Reduces need for
solid paint waste .
disposal






* Eliminates solvent
in coating (no
VOC)
*ls 100%
reactive liquid


,



Reported
Application
+ Steel
^Aluminum
*Zinc and- brass
castings











* Some metal
applications
* Filler for •
chipboard
+Wood
>" Wet look"
finishes.
.,



Operational
Benefits
* Can apply thick
coat in one
application
+ Requires no
mixing or
stirring.
* Has efficient
material use
(i.e., nearly
1 00% transfer
efficiency)




* Can apply thin
coat
•* Has easy color
blending or
changing
4- Has efficient
material use
(i.e., nearly
100% transfer
, efficiency)


Limitations
* Requires special"
handling of heated
parts
* Has electrostatic
application systems
that must be
electrically
conductive; complex
. shapes difficult fb.coal.
+ Needs special equip-
ment or extra effort to
make color changes
* Is difficult to incorpo-
'.rate metal flake
pigments
* Has styrene volatility
* Is typically best
applied to flat
materials
* Is limited te thin
coatings
*Has high capital
cost of equipment
+ Can have yellow
. color
        "High-solids formulations do reduce solvent in the coating when compared with low-solids formulations. In many cases,
        however, high-solids coatings represent the baseline for regulatory limits, and low-solids no longer comply. For this reason,
        high-solids are considered the baseline for solvent content, and consequently do not have a reduced solvent content '
        even though they qualify as a cleaner technology compared to traditional low-solids coatings.
        smaller amount of solvent in the coating mixture
        means a smaller amount will be available to clean
        the substrate (TURIb, p. 9).

        Types  of High-Solids  Coatings

        High-solids coatings fit into 3 general categories:
        air/force dry, baking and two-component.

        Air/force dry coatings cure by exposure to
        moisture or oxygen at temperatures less than
         194*F. Alkyd resins are most common in air-dry
        coatings. Air-dry alkyds are often termed oxidizing
 of auto-oxidizing because they cure in air without
 baking or the addition of a catalyst. However,
. low-temperature ovens can be used to speed cure.
 The recent development of new acrylic resins has
 resulted in a range of fast-drying high-solids paints
 suitable for general metal finishing applications,-
 both indoor and outdoor. These coatings are
 inexpensive, offer excellent flow and drying
 properties, good hardness, durability, color and
 gloss stability, and do not suffer from air entrap-
 ment or sagging (EPAd,.p.'16).
                                                      64

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                                                                  Chapter 6: Alternatives to Solvent-Borne Coatings
Bake coatings predominately use acrylic and
polyester resins, although some alkyds and
modified alkyds.are also used. These resin
systems cure in an oven at high temperatures (350
to 400°F) to form a crosslinked film. Crpsslinking
agents, such as melamine-formaldehyde (MF) or
blocked isocyanates, are commonly used. MF
coatings are usually one-pack systems, catalyzed
by a strong acid, such a p-toluenesulfonic acid.
Latent of blocked catalysts are used for fast cure
and good pot life. Blocked isocyanates, such as
aliphatic polyisocyanates, are recommended for
coatings requiring superior weathering properties .
and resistance to yellowing (EPAd, p. 16-17).

In a fwo-componenf reactive liquid coating
system, two low-viscosity liquids are mixed just
before application. One liquid contains reactive
resins, and the other contains an activator or
catalyst that promotes polymerization of the resins
(NCP2P, p. 4). However, once the two compo-
nents are brought together, curing starts; therefore,
these coatings have very short pot lives after
mixing. Short pot life can be overcome by using a
twin-headed sprayer that is fed from two different
pots. This spray head can proportion the flow of
each component to achieve the desired ratio of
liquids. Thus, the two components mix both on
the way to the workpiece and on the workpiece
itself (VT DEC).          ..

Two-component coatings cure at low tempera-
tures, and do not require heating in ovens
(MnTAP, p. 4). Epoxies and polyurethanes are the
most-common two-component systems. Epoxies
 are the oldest form of high-solids coatings,
 producing thick films for specialty applications.
 Two-component polyurethane coatings are
 suitable for use in the automotive and machine
 tool industries because of their excellent resistance
 to solvents, lubricants, cutting oils and other
 chemicals However, polyurethane coatings do,
 pose some health and safety concerns. For
 example, polyisocyanates used as crosslinking
 agents in polyurethane coatings can impair the
 respiratory function, causing sensitization and in
 some.cases, permanent lung damage (EPAd, p.
 17-18).        •
Application  Methods

High-solids coatings usually are applied by con-
ventional spray guns. Traditionally, the high
viscosity of high-solids coatings have made them
difficult to atomize, making it difficult to achieve a
uniform film thickness. Today, emerging formula-
tions are tending toward lower viscosities and,
therefore, easier spraying. These new formula-
tions might be based on new resin systems, or
additives that modify viscosity and rheology for
easier spraying (EPAd, p. 18-19). In addition, the
use of a heated spraying system can also reduce
viscosity (VT DEC).     ,

Paint Heaters

If the viscosity of the paint needs adjustment
before it can be sprayed, companies generally thin
the coating with solvents. Using solvents for
thinning increases air emissions and requires the
purchase of additional materials. An alternative
method for reducing viscosity.is to use heat. The
benefits from the purchase of paint heaters can
include lower solvent use, lower solvent emis-
sions, more consistent viscosities and faster curing
rates (MnTAP,  p, 3).

Most heaters are stainless steel and are placed
between the pump and spray gun. The heaters
work best on recirculating systems that return
heated material to the container when operators
are not spraying. These systems keep the tem-
perature and viscosity constant and avoid cooking
the material when spraying stops (MnTAPc, p. 6).

 Markets

 With the exception of two-component liquid
 coatings, which are widely used for auto and
 appliance painting (IWRCb, p, 26), high-solids
 paints have not made the inroads that other
 systems (such as powder coatings) have hi  .
 replacing conventional coatings in product coatings
 applications. Particular problems have included
 high viscosity, viscosity changes due to tempera-
 ture variation, and storage stability, as well as the
 control of film thickness and the drying character-
 istics of the film (EPAd, p. 15). A variety of new
 formulations, however, could mean increased
 growth in a wider variety of markets.
                                              65

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Chapter 6: Alternatives to Solvent-Home Coatings
       New  Developments

       100% So/ids Coatings. Because these materials
       are basically solids, their most distinguishing
       feature is their viscosity. The 100% solids coatings
       have a viscosity at room temperature that is
       approximately 10 times greater than other paint
       coatings. These materials are not formulated with
       heavy metals, HAPs or added solvents. Further-  .
       more, once cured, they can be disposed of as
       nonhazardous solid waste. Because 100% solids
       coatings have very high viscosities, conventional
       handling and  application methods are ineffective.
       Instead, mechanical agitation is needed to reduce
       the viscosity of the coating, making it easy to
       apply. Increasing the temperature can also reduce.
       viscosity as these coatings are extremely heat
       sensitive (e.g., an additional 20T can reduce
       viscosity by.50%). Application techniques include
       electrostatic spraying, airless application, roller
       application and dip tanks. Using these methods the
       material can be applied in thin layers, providing
       excellent coverage of the painted object (APC, p.
       1.12).

       Cost  and Implementation Issues

       The high-solids coatings that are currently avail-
       able are generally similar to low-solids coatings in
       their application, curing and final film properties,
       and the capital cost for application equipment is
       approximately the same. The high-solids coatings
       themselves are slightly more expensive; however,
  pollution control costs may be lower. In addition,
  a paint heater might be required (EPAd, p. 15-21).
  In many cases, high-solids coatings represent the
  baseline for regulatory limits, and conventional
  solvent-based, low-solids coatings no longer
  comply (EPAd, p. 12).

  Waterborne Coatings

  General  Description

  The term waterborne refers to coating systems
  that primarily use water as the solvent to disperse
  the resin (IHWRIC, p. iv). Usually, they contain
  up to 80% water with small amounts of other
  solvents, such as glycol ethers (TURI, p. 1). Most
  regulations require waterborne coatings to have a
   CASE STUDY:
   Freightliner Truck Manufacturing

   In 1989, Freightliner Truck Manufacturing's
   plant in North Carolina substituted high-solids
   paints for conventional solvent-borne coat-
   ings. This increased transfer efficiency while
   reducing VOC emissions and paint wastes by
   30%.

   * Savings
   The substitution resulted in savings of $28,000
   in paint purchases and paint disposal costs   ,
   (TURIb,p.9).
         Table 20.  Advantages and Disadvantages of High-Solids Coatings
                     (NCP2P, p. 2)
         Advantages
 Disadvantages
           Reduces VOC and HAP emissions
         * Reduces solvent use
           Reduces inventory
           Reduces fire hazards
           Reduces number of spray applications to
           achieve a given film thickness
           Improves  abrasion and mar resistance
          • Reduces environmental, safety and
           odor problems
           Compatible for use with conventional
           spray equipment
           Decreases energy costs associated with
           reduced curing times
. 4 Generally requires high cure temperatures
 * Is sensitive to inadequate cleaning of substrate
 * Is extremely sensitive to temperature and humidity
 * Is difficult to control film thickness
 4 Has tacky overspray; difficult to clean
 '•» Might require paint heater in system
 * Is difficult to control sagging
 *Has narrow "time-temperature-cure" window.
 * Cannot use dip or flow coating
 *ls difficult to repair.
 * Solvent use not completely eliminated
 * Has shorter potrlife than conventional coatings
                                                  66

-------
 VOC content of less than 3:5 pounds per gallon  ,
'less water (EPAd, p. 47).,

 Advantages  and  Disadvantages

 In addition to reducing VOC emissions during.
 application, waterborne coatings reduce risk of
 fire, are easier to clean up (creating less hazardous
 residues) "and result in reduced worker exposure to
 organic vapors (EPAd, p. 46-52). However,
 special equipment might be required for applica-
 tion, as water in the formulation can cause
 corrosion. For instance, water-based paints can
 rust plain steel or attack aluminum; therefore,
 application equipment must be constructed of a
' corrosion-resistant material such as 316 stainless
 steel. Humidity, must .also be controlled to achieve
 the best film formation"; a microprocessor-con-
 trolled water-spray system is one method for
 doing so (EPAd, p. 52), For more information on
 other advantages and disadvantages.of waterborne
 coatings, see the box at the end of this section.

 Types  of Waterborne Coatings

 Almost all types of resins are available in a •
 waterborne version, including vinyls, two-compo-
 nent acrylics, epoxies, polyesters, styrene-butadi-
 ene, amine-solubilized, carboxyl-terminated alkyd
  and urethanes (EPAd, p. 47-48). Waterborne
  coatings are classified  based on how the'resin is
  fluidized (KSBEAP, p. 6). The three main types
 .are:, water-soiuble/water-reducible (solutions),
  water-dispersible/colloidal (dispersions) and
  emulsions (latex) paints (the most commonly used
  form) (TURI j. Within  each category, physical
  properties and performance depend on which ;
  resins, are used (KSBEAP, p. 6).2

  Water-solub/e paints are paints whose individual
  molecules of water-soluble resins dissolve com-
  pletely in waten Water-soluble resins are generally
  produced via polycondensation or polymerization
•  reactions in an organic medium. As a result, they  .
  generally contain organic co-solvents like alcohols,
   glycol ethers or other oxygen-containing solvents
.   that are soluble or rniscible with water (organic
   content less than 10 to 15%). Because of viscosity
   anomalies, waterborne paints made with water-
 .  soluble binders have only about 30 to 40% solids
                                                                   Chapter 6: Alternatives to Solvent-Borne .Coatings
content by weight. Resins include alkyds, polyes-
ters, polyacrylates, epoxies and epoxy esters.
Despite their sensitivity to water, water-soluble
paints have a high gloss and a high level of
corrosion protection, along with good pigment,
wetting and stabilization (EPA, p. 160).

Wafer-d/spersib/e paints, or colloidal coatings, are
paints that have small clusters of insoluble resin
particles that are suspended in water. Mechanical
agitation is sufficient to suspend the clusters
(KSBEAP, p. 7). Small amounts of organic
solvents (usually less than 5% by weight) are used
as coalescing agents that evaporate on drying,
Resins used in dispersion paints include vinyl
acetate copolymers, vinyl propionate copolymers,
acrylate-methacrylate copolymers, and styrerie-
butadiene copolymers and polymers (EPA, p.  .
 161). Colloidal dispersions are used mainly to coat
porpus materials such as paper or leather (EPAd,
P-'49).          /.    '     -

 Emulsions, or as they are more commonly known,
 latex paints, are similar to water-dispersibles.
 However, resin clusters;in emulsions tend to be
 larger, and an emulsifier is required to keep the
 clusters in suspension (KSBEAP, p. 7). Emulsion
 paints are manufactured using a variety of resins
 including styrene-butadiene copolymers, poly vinyl
 acetate (the most common), acrylics, alkyds and
 polystyrene. Emulsion paints are widely used in
 the architectural market segment (IHWRIC, p; 6).
 The increased permeability of latex paints allows
 these coatings to "breathe," reducing the chances
 for blistering or peeling (EPA, p. 16-1).

 Wafer-based alkyds may take longer to dry than
 solvent-borne coatins, but the resulting coatings
 have similar gloss, flow and leveling properties.
 These coatings are extremely versatile because
 they are thinned with water to almost any viscos-
 ity. They can be applied with spray or dip applica-
 tions and are among the least expensive VOC
 compliant coatings (CAGE).

  Application  Methods

  Application technology for waterborne coatings is
  comparable to that of conventional solvent-borne
   2 For more information on the advantages and disadvantages of each resin type see, "High-Solids, Low VOC, Solvent-
   based Coatings," by Ron Joseph, part of. the Mefal Finishing Special: Organics Finishing Guidebook and Directory.
                                                67

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Qupter 6: Alternatives to Solvent-Borne Coatings
       Figure 4.  Major Resin Fluidization Methods (KSBEAP p.8)
                      Solution
                        Paint
                    Individual separate
                        molecules
 Emulsion
    Paint
 Large 'clustered*
 groups of 50-75
 molecules, each
coated with a layer
of emulsifying agent
Dispersion
   Paint
 Small 'clustered*
 groups of 10-25
   molecules
        coatings. If a facility is using a water wash booth,
        overspray is easily recovered and reused if colors
        are appropriately segregated. Uncured waterborne
        coatings can be cleaned from equipment with
        water (TURI, p. 1).

        Electrostatic spray can be used if the electrically
        conductive waterborne paint is isolated from the
        electrostatic system. Three methods can be used
        to avoid grounding out the electrostatics in a
        waterborne system. The facility can (1) isolate the
        entire paint system from electrical grounds; (2)
        isolate a small part of the wetted system with a
        voltage blocking device; and (3) indirectly charge
        the paint particles away from any wetted equip-
        ment. Each method has its own advantages and
        disadvantages and should be evaluated for the
        specific application. The use of a voltage blocking
        device at each atomizer is often the most cost-
        effective method (EPAd, p. 51)  (VT DEC).

        Waterborne coatings can also be applied by
        electrodeposition for corrosion resistance and
        coating of hard-to-reach areas (TURI, p. 1).
        However, some formulations or substrates might
        require  special pumps and piping to prevent
        corrosion from water in the formulation. In '
        addition, for product finishing, coatings need to
        dry or cure at elevated temperatures to ensure
        complete cure in a reasonable period of time.
        Therefore ovens are required with this process
        (EPAd, p. 52).
          Markets

          Waterbome coatings have quickly taken hold in
          some product-coating market segments; for more
          than two decades, copiers, fax machines, type-
          writers, printers and computers have been painted
          with various combinations of waterborne emulsion
          and other coatings (McBree et al., p. 35).  How-  •
          ever, waterborne coatings have been less accepted
          in market sectors with requirements that are
          exceptionally high for appearance and engineering.
          In recent years, however, the automotive OEM
          sector has increased its use of water-based paints
          and coatings in all but the heaviest coat applica-
         . tions. An estimated 20% of this sector now uses
          water-based paints, and that percentage is growing
          each year. With improved water-based paint
          technology, manufacturers have been able to
          change from solvent-borne paint systems and
          meet emissions regulations while maintaining their
          ultrahigh finish standards (EPA; p. 162).

          New Developments

          Waferborne Two-Comp.onenf Technology. With
          this new technology, coatings manufacturers can
          formulate high-performance coatings without
          cosolvents and achieve the same appearance,
          properties and ease of use that manufacturers
          have with the solvent-borne analogs. For example,
           an epoxy curing agent for water-based epoxy
           coating formulations has been designed for use
           with solid epoxy dispersions. This epoxy curing
                                                     68

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                                                               Chapter 6: Alternatives to Solvent-Borne Coating-
agent provides corrosion resistance when used as
a primer in general metal applications (Iceman, p.
27).        •       '           '•''•'".'•

Cost  and  Implementation  Issues

Waterborne coatings are more expensive than
conventional^coatings per unit of reactive resins.
In addition, the capital costs for application
equipment tends to be greater (e.g., stainless steel
is required to protect against corrosion in storage
tanks and transfer piping). However, water-based
coatings generally use less organic solvents,
reducing environmental and human health risks
(EPAd, p. 58-60). Technical assistance providers
should remember that, despite the use of water in
waterjrarne formulations, discharge of wastes
from coatings must still be in compliance with
federal and state wastewater discharge regulations.
Paint manufacturers, however, are developing
methods for recycling waterborne paints col-
   CASi STUDY:
   ESCO Elevators

   ESCO Elevators is an elevator manufacturer
   with 225 employees located in Forth Worth,
   Texas. They identified a waterborne coating
   that could reduce VOC emissions and
   maintain production quality! To ensure that
   the coating complied with all environmental
   standards, ESCO asked the Fort Worth Water
   Department to determine if the waste gener-
   -ated by this coating could be discharged to
   the city's sewer system. The waste was tested
   and approved by the city; -which noted that
   the waste helped balance the sewer system's
   pH level. To ensure that dust generated from
   the water-based paint could be disposed of
   in landfills, ESCO also had to administer a
   1C.L.R test for the paint dust.

   * Savings
   By substituting waterborne coatings for
   solvent-based coatings, ESCO Elevators was
   able to reduce its VOC emissions by 10,764
   pounds per year. ESCO also saved between
    $20,000 and $30,000 peryearby elimina-
   tion of hazardous waste disposal costs.
   Additional savings came from lower fire
    insurance premiums and reductions in
    reporting requirements for EPA (PPIFTI). -
 CASE STUDY:
 Metal Lab Furniture Manufacturer

 This facility is a manufacturer of metah
 laboratory furniture, including base cabinets,
 wall cases and fume hoods. The facility
 produces 3,500 units of furniture a year with
 sales of $3,000,000 annually. Production  •
 processes include punching, forming,
 cleaning, phosphatizing and painting. Waste
 streams generated by these processes
 included solvent waste and paint sludge. The
 facility implemented a switch from  solvent-
 based paints to qqueo'us-based paints to
 minimize both the volume-ahd toxicity of their
 waste streams. The company chose an
 acrylic enamel paihtfor use that is not only
 nonhazardous but has a longer shelf life
 than conventional solvent-based paints.

 * Savings  -.'-.-.
 Investments in this system included purchas-
 ing electrostatic spray equipment and
 | retraining operators. The enamel  paint is  .
  more expensive than the solvent-based
  paint, but because it can be dried at lower
 temperatures the company has realized
  savings in energy costs. The company  has
  also reduced its hazardous waste generation
  by 75%, and because the paint has a longer
  shelf life, less obsolete paint is disposed (VT
  DEC).
 lected from communities and industry (EPA, p.
 162),    ',  .                .,.  -.

 Powder  Coating:

 General  Description
 Powder coating uses 100% resin in a dry, pow-
 dered form (MnTAP, p. 4). Powder coating works
 on the principle that opposite charges attract. The
 powder is pneumatically fed from a reservoir
 through a spray gun where the powder gains a low
 amperage, high-voltage positive charge. Parts to
.be painted are electrically grounded so that the
 positively charged powder particles are strongly .
 attracted to the parts' surfaces. The powder-
 ' coated part is then pulled through an oven where
                                              69

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Chapter 6: Alternatives to Solvent-Borne Coatings'
       Table 21.  Advantages and Disadvantages of Waterborne Coatings
                   (NCP2P, p. 2)
       Advantages
                                          Disadvantages
  Reduces VOC and HAP emissions
* Can use conventional application processes
  Reduces toxiciry and odor, resulting in
  improved worker safety and comfort
      good storage life
*• Is easy to clean up
* Minimizes or eliminates disposal of
  hazardous waste.                 '
+ Has good to excellent surface properties,
  including gloss, rub resistance, anti-sealing
  effects and non-yellowing film
|+ Can recover and reuse some waterborne
  paints, increasing transfer efficiency
* Some dried waterborne paint waste may be
  disposed of in a landfill as non-hazardous
  waste
                                                 * Has tendency to foam
                                                   Requires clean surface for high quality
                                                   application; surface must be free of oil and dust
                                                 + Requires longer drying times or increased
                                                   oven temperatures
                                                 *Has difficulty obtaining high gloss finish
                                                 * Has difficult cleanup once coating is cured
                                                 + Has great susceptibility to dirt pickup
                                                 + Has higher cost per gallon on an equivalent
                                                   solids basis compared with conventional coating
                                                 *Does not have many resins available for
                                                   waterborne formulations
                                                 *ls complex to convert solvent-borne coating line,
                                                   i.e., stainless steel, plastic lines, valves and
                                                   other ancillary equipment are  needed  ,
                                                 *Has problems with atomization,  i.e., reduced
                                                   paint transfer efficiencies
                                                 * Increases runs and sags
                                                 * Requires good temperature/humidity control
                                                 * Requires storage area enclosure and heating
                                                   (i.e., repeated freezing and thawing will damage
                                                   the coating).
                                                  * Is difficult to refinish                   .
                                                  •* Has reduced temperature resistance
                                                   Can have poor penetration and adhesion  proper-
                                                   ties, particularly with emulsion coatings on porous
                                                   surfaces'
        the powder melts and fiases into a smooth coating
        (IHWRICe). Substrates must generally be able to
        withstand temperatures of 260T or higher (EPAd,
        p-33).
                                              the pomplete conversion of a coating line, which
                                              can be costly. For more information on other
                                              advantages and disadvantages of powder coating,
                                              see table 23 at the end of this section.
        Advantages  and  Disadvantages      Types  of Powder  Coatings
        Powder-coating materials can provide a high-
        quality, durable, corrosion-resistant coating.
        Powder coatings do not produce hazardous
        overspray wastes or wastewater sludges, and most
       ' do not release VOCs when cured (some powder
        coatings will release VOCs, such as caprolactam, a
        former HAP). With powder coating, users can
        collect the powder overspray and reuse it, result-
        ing in transfer efficiencies of up to 99% (MnTAP,
        p. 4). However, powder coating systems require
                                              Product manufacturers can specify the properties
                                              required in a finish (such as resistance to ultravio-
                                              let light, high durability, corrosion resistance and
                                              color) to a powder coating manufacturer who then
                                              formulates the appropriate powder (HIWRICe).
                                              Coating powders are frequently separated into
                                              decorative and functional grades; decorative
                                              grades generally have a finer particle size than
                                              •functional grades. Powders are also divided
                                              between thermpset and thermoplastic resins
                                              (EPA, p.  163-164).
                                                   70

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                                                                  Chapter 6: Alternatives to Sotvent-Bome Coatings
 Thermoset resins crosslink to form a permanent
 film that withstands heat and cannot be remelted.
 They are used for decorative and protective
 coatings for architectural structures, on appliances
 and furniture, and elsewhere. Thermosetting
 resins are characterized by their excellent adhesion
 to metal; they are one-coat systems and do not
 requires primer (Farrelr, p. 81). The five basic
 families of thermoset resins are epoxies, hybrids,
 urethane polyesters, acrylics and triglycidyl
: isocyanurate (TGIC) polyesters as described
 below:

 •* Epoxies are used for both functional and
   decorative coatings. Their functional properties
 ,  include outstanding corrosion resistance and
   electrical insulation. Decorative epoxies offer
   attractive finishes that are flexible, tough, and
   have excellent corrosion-resistance and-high-
   impact strength. However, these coatings lack
   ultraviolet resistance and, therefore, are not
   recommended for outdoor use. In prolonged
   exposure to sunlight, they tend to chalk and
 ' discolor. Various types of hardeners are used
   with epoxy powder to optimize its properties.

  •* Epoxy polyester hybrid coatings are mainly
   used for decorative applications. They are
   more resistant to chalking and over-bake  .  .  •.
  ' yellowing  than pure epoxies, but have a lower
   surface-hardness and; are I ess-resistant to
   solvents. They exhibit better transfer efficiency "
 .. and a greater degree of penetration into
   recessed areas of a part than other resins.

  * Urethane polyesters are formulated with
    polyester hydroxyl resin combined with blocked
    isocyanate hardeners. They exhibit outstanding
   thin film appearance and toughness as well as
    good weathering properties.

  +Acry/ic-urefhane coatings are formulated with
    acrylic resins crosslinked with blocked isocyan-
    qtes. They have excellent color, gloss, hard--
    ness, weatherability and chemical resistance,
   .and have an excellentth'rn film appearance.
    However, they are less flexible than polyesters.

  . * TGIC polyesters contain a polyester resin
    crosslinked with TGIC as a -curing agent.
    They offer very good mechanical properties,  .
    impact strength and weather resistance. They-
  a re'resistant to chalking and are often used
  for outdoor parts, such as patio furniture,
  lawn mowers, as well as aluminum extrusions
  and panels for large commercial buildings. In
  Europe, reduced occupational-exposure •
  limits were recommended for TGIC powders
  as a result of in vivo mutagenjcify tests (EPAd,
  P-28}.          ;                  -   . .

Thermop/asfic resins form a coating, but do not
undergo a change in molecular structure. These
resins can be remelted after they have been
applied. Thermoplastic powder coatings melt and
flow when heat is applied, but retain the same
chemical composition when they .are cool and
solidified (KSBEAP, p,: 10). Although Some
thermoplastic materials provide adhesion to metal,
.most require a primer (Farrell, p. 81). Thermo-
plastic resins are mainly used in functional coat-
ings, such as thick, protective coatings on
dishwasher trays. Examples of thermoplastic   '  '
resins useci in powder coating are polyethylene,:
polypropylene, nylon, polyvinyl chloride (PVC),
and thermoplastic polyester. These examples are
described below:

* Po/yefhy/ene provides excellent chemical
   resistance and outstanding electrical insulation
 •  properties. These coatings are smooth, and
   have a medium gloss and good release,
   properties that allow sticky materials to be
   cleaned from their surfaces. These are often
   used as coatings for laboratory equipment.

 * Po/ypropy/ene produces a surface that is very
   inert and is often used in applications where •
   the part that is powder coated might be
   exposed to chemicals.

 VNy/on offers excellent abrasion, wear and "
   impact resistance, and a low coefficient of
   friction. Nylon is commonly used  as a me-
   chanical coating for sliding and rotating
   bearing applications-in appliances, farm
 • equipment and textile machinery.

  * PVC provides good durability as  well as
   • flexibility; dishwasher trays are an example of
    a product coated with PVC.  .

  *• Thermoplastic polyester offers good exterior
    durability and weatherability. The coating  does
                                               71

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Chapter 6: Alternatives to Solvent-Borne Coating
  not usually require a primer for good adhe-
  sion to most metals. These materials are
  often used on outdoor metal furniture (EPAd,
  p. 26 and PCI, p. 6-7).
 See table 24 for a summary of powder coating
 resin properties.

 Application Methods

 There are five powder coating processes: electro-
 static spraying, fluidized bed, electrostatic fluid-
 ized bed, flame spray, and tribocharge.

 Electrostatic Spraying

 The main method in use today for the application
 of powder coatings is the electrostatic process. In
 the electrostatic process, electrostatic spray guns
 impart an electrostatic charge to the powder being
 sprayed via a charging electrode that is located at
 the front of the spray gun. This technique is called
 "corona charging," and these guns generate a
 high-voltage, low-amperage electrostatic field
 between the electrode and the product being
 coated. The charge on the electrode can be
 controlled by the operator. Powder particles
 become charged as they pass through the ionized
 electrostatic field, which controls the deposition
' rate and the powder's location on the part. The
 field can be adjusted to direct the powder's flow,
 control pattern size, shape, and powder density as
 it is released from  the gun (KSBEAP, p. 14). The
 particles are attracted and held to the grounded
  substrate through electrostatic forces. The sub-
  strate subsequently is heated in an oven, or
  through chemical activation (e.g., by infrared), to
  fuse the particles to the substrate and to each
  other to create a continuous film (EPA, p. 164).
  This method has made it possible to apply thin
  layers of coatings  for higher quality decorative
  finishes, and has allowed powders to be used on
  parts that should not be dipped in a fluidized bed.

  Powder is supplied to the electrostatic spray gun
  by the powder delivery system. This system
  consists of a powder storage container, or feed
  hopper, and a pumping device that transports a
  stream of powder into hoses or feed tubes.
  Compressed air is often used as a pump because
  aids in separating  the powder into individual
  particles for easier transport. The powder
  delivery system is usually capable of supplying
                                                      powder to one or several guns. Delivery systems
                                                      are used in many different sizes, depending on
                                                      the application, number of guns to be supplied,
                                                      and volume of powder to be sprayed in a given
                                                      time period. Recent improvements in powder
                                                      delivery systems, coupled with better powder
                                                      .chemistries that reduce clumping, have made
                                                     • delivery of a consistent flow of particles to the'
                                                      spray gun possible. Agitating or fluidizing the.
                                                      powder in the feed hopper also helps prevent
                                                      clogging  or clumping of the powder before it
                                                      enters the transport lines (KSBEAP, p. 9).
                                                      Innovations in powder delivery systems also .
                                                      allow the powder supply reservoir to be switched
                                                      easily to  another, color when necessary. Systems
                                                      are also available for segregating colors so that
                                                      several colors can be applied.in the same booth
                                                      (EPAd, p. 36).

                                                      Fluidized Bed

                                                      Initially,  powder was applied using a fluidized bed
                                                      process in which heated parts were dipped into a
                                                     . vat-with  the suspended coating powders.  As
                                                      these particles came in contact with heated parts
                                                      they softened and began to "flow" into other   •
                                                      particles to create a coating. The coatings .were
                                                     . thick, usually vinyl or epoxy, and demonstrated
                                                      functional rather than decorative qualities
                                                       (KSBEAP, p. 9). However, several methods for
                                                      powder  coating exist now, which makes powder
                                                       coating a more versatile option, however fluidized
                                                       bed is still used in certain operations.

                                                       In a fluidized bed, powder particles are kept in
                                                       suspension by an air stream. A preheated
                                                       workpiece is placed in the fluidized bed where
                                                       the particles coming in contact with the
                                                       workpiece melt and adhere to its surface. Coat-
                                                       ing thickness depends on the temperature and •
                                                       heat capacity of the workpiece, and its residence
                                                       time in  the bed. Postheating is generally not
                                                       required when applying thermoplastic powder
                                                       coatings. However, postheating is required to
                                                       cure thermoset powder coatings completely
                                                       (NEFSC).

                                                        Electrostatic Fluidized Bed

                                                     {   An electrostatic fluidized bed is similar in design
                                                        to conventional fluidized beds, but its air stream is
                                                        electrically charged as it enters the bed. The
                                                        ionized air charges the particles as they  move
                                                     72

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                                                              Chapter 6: Alternatives to Sgtvent-Bome Coatings
Table 22. Characteristics of Powder Coating Techniques (Misev, p. 350)
Characteristic
of Workpiece
Size
Material
Temperature
Resistance
Aesthetic Value-
Coating Thickness
Type of Coatings
Color Change
Capital Investment
Labor
Energy
Consumption
Coating Waste
Electrostatic
Spray
Larger .
Metallic, must be
co'nductive
Relatively high ,
High
Thinner films •
Therrnoplasts and
thermosets
Difficult
Moderate to high
low because highly
automated
Only postheating
Very little
Fluidized Bed
or Electrostatic
Fluidized Bed
Smaller-
Any, except wood, rtot
necessarily conductive
' High.
Low, not suitable for '
decorative purposes
Thjck high-build films -
.with excellent uniformity
Thermoplastic and
thermosets
Relatively difficult
Low
Moderate depending on
the automatization
Preheating and often
, postheating.
Very little
." . t
Flame Spray
Not limited
Any, not necessarily
conductive
Not relevant .
Low, not suitable for
decorative purposes
Thick high-build films; •
uniformity depends'
• on the operator
Thermoplastsbnly ,
Easy
Very low
Relatively high
Low, no preheating
or postheating
Depends on the
workpiece geometry
upward in the bed, forming a cloud of charged
particles. The grounded workpiece is covered by
the charged particles as it enters the chamber.
No preheating of .the workpiece is required.
However, curing of the coating is necessary. This
technology is mcst suitable for coating small
objects with simple geometries (NEFSC).

Flame Spray

Flame spray was recently developed for applica-
tion of thermoplastic powder coatings. The
thermoplastic powder is fluidized by compressed
air and fed into a flame gun where it is injected
through a flame of propane, which melts the . ..
powder. The molten coating particles are depos-
ited on the workpiece and form a film upon
solidification. Because no direct heating of the
workpiece is required, this technique is suitable for
applying coatings to most substrates. Metal, wood,
rubber and masonry can be coated successfully
using this technique. This technology is also
suitable for coating large or permanently fixed
objects (NEFSC).    -       .

Tribocharge

Tribocharging relies on friction between the
powder and the spray gun. The. action of the
powder flowing through the barrel of the gun
                                            73

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Chapter 6: Alternatives to Solvent-Borne Coatings
       generates a frictional charge on the powder. The
       charged powder is carried by the air stream to the
       substrate, where it adheres due to electrostatic
       attraction. Because no high-voltage system is
       used, the electric field is substantially smaller and
       the powder tends to follow air currents rather than
       field lines. The smaller electric field results in a
       much reduced Faraday cage effect3. Conse-
       quently, tribo guns produce smoother finishes,
       allow deposition of thicker films, and provide
       better coverage of intricately-shaped objects
       (EPAd.p. 31).

       Markets

       Currently, 85% of the total market for powder
       coatings is represented by four industrial areas:
       metal finishing (53%), appliances (21%), lawn and
       garden (8%), and architectural applications (3%)
       (EPA, p. 164).

       Since 1986, all ormost automotive manufacturers,
       have powder coated engine blocks, the largest
       volume job in the history of the powder industry.
       Now powder has come out from "under the
       hood" and is  being used on a wide range of trim
       and accent parts. Polyester and acrylic powders
       are used in these coatings. For example, the
       "metallic look" powders are delivering luster to
       aluminum wheels. However, there remains great
       potential for  more powder use in the automotive
       industry; its use as a primer surface and anti-chip
       coating on body panels is becoming more com-
       mon. Powder coatings have undergone extensive
       testing both as a primer surfacer and antichip
       coating and have met OEM standards for chip
       resistance, adhesion, durability, and heat and
       humidity exposure.

        In addition, clear powders over liquid base coats
        are currently being tested for exterior auto body •
        finishing. The advent of clearcoat finishes for base
        coats in the mid-1980s made it more economically
        feasible to use powder as an automotive topcoat.
        Using specially formulated acrylic and polyester
        powders, manufacturers are working to meet the
        automotive industry standard for clearcoats of
        absolute smoothness, clarity, perfection and
        performance (Bocchi, p. 21).
New  Developments

Con Coating. Development of powder coatings
for the coating of can interiors, tops, ends and lids
is well underway. In addition, application equip-
ment is now available to apply, recover and
recycle the very small particle size powders
required to maintain thin films and run at line
speeds common in this industry. Food and Drug
Administration approval is still pending.

Lower-Temperature Cures, Powder coatings with
very high reactivity have been developed to cure
at temperatures as low as 121°C (250°F). Such
low-curing powders will allow more types of
products to be coated with powder, including
plastics and preassembled products that contain
heat-sensitive fluids or gaskets. In addition,
manufacturers can run higher line speeds with the
lower-cure powders, thereby increasing produc^
tion capacity.

Weathering Capabilities. Significant advances
have been made in the development of polyester
and acrylic resin systems with excellent long-term
weatherability, which is needed to meet the
extended warranties being offered by manufactur-
ers. Also under development are fluorocarbon-
based powders that will match or exceed the
weatherability of liquid fluorpcarbons, with
application costs similar to or lower than conven-
tional powder coatings.

Thinner Films. Powder manufacturers are continu-
ally working to develop powders that can form
films that are thinner than those previously
attainable, resulting in a savings of material and
money. Based on epoxy-polyester hybrids, these-
powder coatings provide applications in the range
 of 1. to 1.2 mils for colors with good hiding
 powder. These thin coatings are currently suitable
 only for indoor applications (Moore, p. 66 and
 Bocchi, p. 32-34).                           '

 Cost and  Implementation  Issues

 Powder coating emits no VOCs and offers ~
 several performance advantages. However, to
, introduce powder coating to an existing paint line,
        3 The Faraday cage effect occurs when the electrostatic-field force limits the entry of paint particles in
        recessed areas. To achieve coating in the recessed area, overpainting of the nonrecessed area or manual
        touchup often is required. In this situation, real transfer efficiency is less than the quoted transfer efficiency.

                                                    74

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                                                               Chapter 6: Alternatives to Solvent-Borne Coatings
a capital investment in special equipment must be
made. Pretreatment of the part to.be coated also
needs to be quite thorough, which can add to the
overall cost (EPAd, p; 35), For entirely newrlines,
however, investment in powder application
equipment is comparable to that of equipment for
liquid coatings (VT DEC). In addition, the cost of
producing a finished coating is typically lower with
-powder coating than conventional coating because
maintenance and operating costs are less, particu-
larly for operations that use a single color (EPAd,
 Radiation Curing:

 General  Description
. Radiation curing uses ultraviolet (UV) and
 electron beam (EB) electromagnetic radiation to
 polymerize specially formulated coatings directly
 on a substrate. Galled photopolymerization, the
 UV-cu,ring process is a photochemical reaction.
 Specially formulated coatings mixed with a small
 amount of materials called photoinitiators are
  exposed to a UV-light source, initiating
  crosslinking. The rate of polymerization depends
  on the intensity of the radiation used (Radtech, p.
  40), EB curing crosslinks coatings by exposing
  them to low-energy electrons; however, because
  of the high cost associated with EB generators,
  this method of radiation curing accounts for only
  about 10 to 15% of the total radiation curing
  market (Lucas, p. 29).              .

  Advantages and  Disadvantages

  Radiation curing produces high-performance
  protective and decorative finishes. Radiation-
  curable coatings can be 100% reactive liquids,
  completely eliminating the use of solvents. How-
  ever, some of the resins in these coatings can
  volatilize, resulting in VOCs; Although emissions
  are usually low, the amount of VOCs emitted
  from radiation curing depends entirely upon the
  coating formulation (EPAd, p. 68). In addition, the
  shape of the part will affect the curing; flat
  surfaces are easiest to cure: Capital investments
  for UV-curing systems' are usually lower than
 Table 23. Advantages and Disadvantages of Powder Coatings (NCP2P, p. 3)
 Advantages
Disadvantages
 * Reduces cost due to:   ;  .'  ..
   '.-no solvent flash required      .   ..  ' -
   -no.coatings mix room needed
   -minimal oven length required,
   -low ventilation required
   -less floor space required, i.e., system
   requires two-thirds to three-quarters of
  . wet paint'systems
   -VOC and HAP,compliant, i.e.; no solvents
 * Improves finish quality
 * Improves finish durability
 * Has good corrosion resistance
 + Has coating utilization efficiencies that
   reach 95 to 99%
 * Saves energy
 •* Requires little operator expertise
 *.Has quick "packageabiiity"
 '•* Has a variety of resins available      .
 * Has, no hazardous overspray, waste sludge
   or contaminated water
  * Reduces worker exposure to solvent vapors
* Has heat requirements that restrict application of
  powder to metal finishing surfaces   -    ,
•* Has powder manufacturing limitations:
  -difficult to make small amounts        .      . .
  -control of texture size and distribution limited
  -metallic powder coatings not as attractive
  as wet metallic finishes   .
* Has recirculating system that creates negative   .
  pressure in booth
* Needs gentle air stream to apply powder •
+ Enhances Faraday cage effect (VT DEC)  .
* Is difficult to achieve thin films below 1.0 to 1.5 mils
* May cause powder clumping
> Is difficult to change colors
* Needs cool, dry storage area
* Must pretreat substrate          .''.'.
                                             75

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Chapter 6: Alternatives to Solvent-Borne Coatings
         CASE STUDY:
         Knoll Group

         The Knoll Group in East Greenville, Pennsyl-
         vania, manufactures office furnishings includ-
         ing office systems, desks, credenzas and
         chairs. Originally, the company applied
         solvent-borne coatings using conventional
         spray techniques. Solvents in the paints
         included toluene and methyl ethyl ketone
         (MEK). When Knoll studied the paint process,
         the company found that paint material loss
         was nearly 80%.

         As a  result, Knoll decided to develop a
         powder coating that would give a high-quality
         finish. Knoll engineers and scientists experi-
         mented with resin and other powder-paint
         components from various national and
         international suppliers to develop the new
         coating. The result was a new powder system
         .that uses approximately 98% of the raw
         coating material. Excess powder is collected,
         cleaned and reused.

         + Savings
         The Knoll group realized a payback of its
         $500,000 investment in less than a year with
         total savings of $639,000 per year. Other
         bonuses  included easier compliance with
         more stringent environmental regulations, anc
         elimination of fees for incineration of solid
         and liquid hazardous waste (OH DEP).
        investments for conventional ovens and use
        considerably less space. The cost of the coating is
        generally higher on a per pound basis, but not
        always on a coverage basis (RadTech). For more
        information on other ad vantages .and disadvan-   .
        tages of radiation curing, see table 25 at the end of
        this section.

        Types  of Radiation-Curable
        Coatings

        A complete formulation for a radiation-curable
        coating consists of a blend or mixture of ojigo-
        mers (low molecular weight polymers), mono-
        mers, additives, pigments, and photoinitiators. The
        oligomer used in the formulation plays an irhpor-.
        tant role in determining the final properties of the
 CASE STUDY:
 Swing-N-Slide Corporation

 Swing-N-Slide Corporation's Newco Fabrica-
 tion Division in Janesville, Wisconsin, is a
 leading manufacturer of build-it-yourself
 swing sets. In 1 989, Newco installed a liquid
 spray system for coatings to replace the dip
 coating .operation that had been used there
 since 1 987. However, company officials
 quickly realized that, while more efficient,
 spray painting resulted in an increase in air
 emissions and hazardous waste generation.
 The Wisconsin Department of Natural
 Resources began enforcement for ai-r permit
 noncompliance and classified the facility as a
 large quantity generator.

 As a result, in 1993, Newco installed a
 powder system to replace the liquid paint  •
 system. The system features 1 0 automatic
 and 2 manual electrostatic spray paint guns.
 The facility has reduced hazardous waste
 generation from 38,350 pounds per year to
 4,800 pounds and has been reclassified as a
 small quantity generator. At the same time,
 production output has tripled.

 * Savings
 The capital costs for the powder system were
  $200,000 with a payback period of  14
  months. Newco estimates savings of
  $ 140,670 annually ($41,000 from elimina-
  tion of hazardous wastestreams, $99,670
  from savings on labor and materials, and'
  $23,000 from savings on paint filter clean-
  ing) (Wl DNR).
 finish (Radtech, p. 40). Resins used in conven-
 tional solvent-based coatings can be'chemically
 modified for use in radiation-cured systems by
 introducing acrylate functionality. The general
 physical and chemical characteristics of the resins
 are retained after modification (EPAd, p. 71.).
 The oligomers most commonly found in today's
. radiation-curable formulations are acrylated
 urethanes, epoxies, polyesters and silicones
 (Radtech, p. 40). Coatings that use acrylated  -
 resins cure by free radical polymerization and
 comprise 8'5% of the total radiation-curable  •
 coatings market (Lucas, p. 28).  ,
                                                    76

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                                                              , Chapter 6: Alternatives to Solvent-Borne Coatings
   Table 24.  Summary of Powder Coating Resin Properties (EPAd, p. 27)
Coating
Property
Hardness
Flexibility
Resistance
to Overbaking
Exterior
Durability
Corrosion '
Protection
Chemical
Resistance
Thin Coat
Colors
Available
Clears
Available
Textures
Available
Epoxies
Excellent
Excellent
Fair
Poor
"V '
Excellent
Excellent
No.
All
Yes
Yes.
Epoxy-
Urethane
Hybrids
Excellent
Excellent
Very good
Poor.
Excellent
.Excellent -
No
•All .'/
No
Yes.
Urethahe
Polyesters
Very good
Yery good
Very good
Very good
Very good
Very good
Yes
All
Yes
Yes
TGIC
Polyesters
Excellent
Excellent
Excellent
Excellent
Excellent
Very good
No
All
')
Yes
Yes
Acrylics
Very good •
Fair
Good
Very good
Fair •
Very good
No
All '
Yes
No
Coatings can also cure by cationic curing, the
polymerization of cycloaliphatic epoxies or vinyl
ethers. Cationic curing is an attractive option
because it withstands pasteurization and promotes
adhesion to metals, even during postforming
operations (Lucas, p. 28-29).

Application  Methods

UVrcured coatings can be applied using tradi-
tional-spray methods, but roll-coating is often
used on flat s,tock'(KSBEAP, p. 11). Varnishes on
two-piece cans, are applied using an offset
process, while curtain coating is used in some
specialty applications (RadTech).
 Markets

 The use of TJV-inks and overprint coatings on
 two-piece metal cans has been commercially
 successful for more than 10 years! Coating of
 three-piece composite and metal-can ends has
 been a commercial reality since the 1970s
• (RadTeeh.p. 14). UV-cured coatings are;widely
 used to provide corrosion resistance to galvanized
 metal tubing. It is also used on metallized plastics.
 In addition, UV-cured coatings have been
 formulated for coil coating, in which outstanding
 resistance and flexibility have been achieved.

 Significant growth in other metal markets could
 occur in the next decade as environmental and
                                             77

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Chapter 6: Alternatives to Sotvent-Bome Coatings
         CASE STUDY:
         Replacing Solvent-Based Paints with Powder Paint

         Miller Electric Manufacturing Company in Appleton, Wisconsin, is the world's largest manufac-
         turer of arc welding equipment and systems. Founded in 1 929, the company employs more than
         1,600 people and operates 1,000,000 square feet of manufacturing space. Responding to
         environmental concerns and a desire to improve corrosion resistance of painted parts, Miller
         modified their liquid painting conveyor line for metal parts by replacing four of their electrostatic
         disk applicator booths with two powder booths.

         The previous system used high-sotids paint and achieved a relatively high transfer efficiency.
         However, in 1 994, nearly 30 tons of VOCs were generated from liquid spray painting opera-
         tions, and paint-related wastes were disposed of at a cost of approximately $20,000.

         * Savings                               .                                  .   '     '
         The new system reduced annual feed stock needs from'13,000 gallons of liquid paint to 80,000
         pounds of powdered paint (equivalent to 9,000 gallons'of liquid paint). Annual waste genera-
         tion was reduced from 60,000'pounds per year of paint-related wastes to 1 5,000 pounds per
         year of paint-related wastes (90% of the remaining waste was from liquid paint processes).
         Additional reductions include 50,000 pounds of VOC air emissions, 40,000 pounds of waste
          paint filters and 5,000 pounds of hazardous waste paint and solvents.

          The new powder painting process cost $545,000 to purchase and install. The  new system
          included a powder paint system, an environmentally controlled application room, oven up-
          grades, and improvements to metal preparation and cleanup. The. new system reduced opera-
          tion and maintenance costs by $87,000 per year. This figure includes savings-in purchasing and
          disposal costs. Due to higher transfer efficiency, the total cost of painting was reduced by 25%
          on a square foot of painting surface, resulting in a payback period of 6.3 years.

          This project was approved based on predicted improvements in quality and environmental
          benefits. Powder painting of parts has significantly improved corrosion resistance and surface
         ' finish quality. Employees have also benefited from the elimination of solvent, use and the powder
          booth's effective dust control system (SHWEC).                           '  •         •
        productivity requirements increase. The use of
        UV curing is growing rapidly for wood finishes,
        medical appliances, consumer products, automo-
        tive head lamp assemblies, optical fibers and
        electronics. Growth will be further enhanced with
        the development of cationic-cured epoxies, which
        provide improved adhesion to, and protection of,
        metal substrates (MFC, p.. 29-36).4

        New  Developments

        Wafer-Redudb/e, UV-/EB-Curable Formula-
        tions. These formulations have been developed
        for a number of coatings and products, including
        flexo and gravure inks, clear coatings for wood
        furniture, and dip-coated or spray-coated plastics.
Water dilution of a compatible resin system
provides lower viscosity, thinner films, improved
flow and leveling, lower applied costs and lower
amounts of monomers and solvents. The use of
water as a viscosity reducer'can minimize or
eliminate the use of lower molecular weight
diluents, which tend to be skin irritants. Some
research has indicated that small amounts of water
(1"% of water) can reduce the viscosity of   .
oligomers substantially, and larger amounts of
water can be used as a  formulation tool to vary
gloss and reduce web temperatures in critical
applications. Disadvantages include the increased
time and energy required to remove, any added
water, as well as the negative effects of water on
         4 For more information on the use of radiation curing in can manufacturing, refer to the EPA document Project
         Summary: Evaluation of Barriers to the Use of Radiation-Cured Coatings in Can Manufacturing.
                                                    78

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                                                               Chapter 6: AltematWes to Solvent-Borne Coatings
the drying and curing system-and the substrate to
which it is applied. If the material is cured before
the water is fully evaporated, then the film
properties will be reduced (Lawson, p. 16).

Cost  and  Implementation Issues

The UV-radiation source most commonly used in
industry is the medium-pressure mercury-elec-
trode arc lamp. These lamps can be retrofitted
easily to existing production lines, but they require
an extraction system to remove excess heat and
ozone that is generated by UV action on oxygen in
the air (EPAd, p. 72). The cost of an electrode arc
system is approximately $6,400 for a 10:inch
lamp, shields to contain the UV light waves that
are harmful to skin and eyes, reflectors, snutters,
a high-voltage power supply, arid an air cooling
fan (EPRI). An alternative UV system produces
UV radiation through microwave excitation of the
mercury vapor (EPAd, p. 72). A microwave-  ,
powered UV-curing system costs approximately
$7,500. This system includes a standard-length
lamp, a power supply, an air cooling system, a
cable, and a detector to ensure that microwave
radiation leaks do not occur (EPRI).

EB  generators are expensive, complex and large.
In addition, oxygen has an inhibiting effect on
crossliriking initiated by EB; therefore, companies
must establish an inert atmosphere of nitrogen,
with oxygen concentrations of less than 100 parts
 per million (ppm) if adequate curing is to be
 achieved (EPAd, p. 72)..   .-

 Emerging

 Technologies

 This section presents coating systems that have:  •
 only recently become commercially available..
 Knowledge of cither technologies that are still
 under research and development is important for
 technical assistance providers. However, present-
 ing information on experimental systems is not
 within the scope of this manual. Technologies
 covered in this section include vapor permeation
 of injection-cured coatings, supercritical carbon
 dioxide and unicoat paint. For more information
 on coating research and development, consult the
 trade journals listed in appendix A.

 Vapor Permeation of /n/ecf/bn-Cured- Coatings
" (VIC). After a.reactive resin is applied as a liquid,
 curing is induced by exposing the liquid to a  .
 vapor-containing compound that initiates polymer-
 ization. Examples are polyol-isocyanate coatings
 that cure by tertiary amine vapor injection
 (NCP2P, p. 4). The amine vapor is made by an
 amine generator in a predetermined concentration
 and is dispersed in an air stream channel in-the
 spray gun. The generator uses dried and filtered
 air at 90 to 120 psi. The coating material and
 catalyst are mixed as they leave the spray gun.
  Table 25. Advantages and Disadvantages of Radiation-Cured Coatings
              (NCP2P,p. 4)
  Advantages
Disadvantages
  * Uses coatings with lower VOC and HAP
    content than conventional coatings
  * Has lower capital investment than
  ' .conventional pveris
  * Increases production rates because
    curing periods are reduced to seconds
  * Has low .energy costs
  > Has consistent performance
  «> Requires small ovens
  + Has low air movement that reduces dust
    and dirt contamination
  + js easily installed/retrofitted
  + Reduces fire and explosion hazard
* Can have interference of photocy re by
  pigments
> Has higher costs for EB and UV coatings
* Has potential problems with acrylate skin
  irritation if proper safety techniques are not used
* Has shrinkage and adhesion problems with •
 'acrylate                 .
* Is not applicable to all finish types because
  it produces a specific "look"
* Has curing sensitive to shape of part
                                            79

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Chapter 6: Alternatives to Solvent-Borne Coatings
         CASE STUDY:
         Adolph Coors Company

         The Coors can manufacturing plant,
         located in Golden, Colorado, is the largest
         single aluminum can manufacturing plant in
         the world, producing approximately 4
         billion cans a year. The plant currently
         produces aluminum cans exclusively for the
         beer beverage market.

         Since 1975, Coors has been using UV
         curing in full-scale can production. The
         initial push to convert to UV was caused by
         a desire to increase can printing speeds,
         reduce e.nergy consumption and lower air
         emissions.

         * Savings
         According to company estimates, the UV
          system saves the firm $90,000 per billion
          cans produced versus conventional technol-
          ogy. In addition, Coors estimates that since
          1975, VOC emissions have been reduced'
          by 1,740 tons (Donhowe). For additional
          information on Coors use of UV curing, see
          EPRIb.
       This technology is a high-solids coating system
       because the coating still uses solvent in the
       formulation. However, its ease of use and rapid
       cure times can improve production efficiency
       (EPAd, p. 80).

       Advantages and Disadvantages

       VIC can produce a variety of finishes with good
       performance characteristics including chemical,
       solvent, and stain resistance; high humidity and
       water resistance; high mar and abrasion resistance;
       and color and gloss retention. These coatings can
be used on a broad range of substrates including
plastic, steel, aluminum, wood and castings. Heat-
sensitive parts such as thermoplastics and thermo-
sets are ideally suited to the low-temperature cure •
used with VIC (EPAd, p. 80). For other advan-
tages and disadvantages of VIC, see table 26.

Cost and  Implementation Issues

VIC is compatible with LVHP, HVLP, electrostatic
and airless spray systems. However, electrostatic
equipment might need to be modified to accom-
modate the amine generator. In addition, some
types of spray guns might have rubber or plastic
seals that degrade when exposed to the amine.
Capacity is limited to two spray guns (EPAd, p.
80).

UN/COAT Paint Technology: The UNICOAT
technology is a one-coat painting system for
aircraft that replaces the combination of a coat
primer system and a top coat system. .Since only
one coat is applied instead of two coats, VOC
emissions- and waste generated from cleanup
operations can be reduced by 50 to 70%. This
technology, developed by the Naval Warfare
Center (NAWC), consists of a self-priming
topcoat for aircraft and other industrial parts.  It is
applied directly to the metal substrate Without
priming (NFESC).

UNICOAT, which is formulated without lead or
chrome, replaces the two-coat system with a
blend of organic and inorganic zinc compounds
that are non-toxic. UNICOAT contains polyure-
thane as do traditional coatings-, however; corro-
 sion inhibitors and adhesion promoters have been
 added to UNICOAT.

 UNICOAT has performed at levels equivalent to,
 and superior to, the performance levels for
          Table 26.  Advantages and Disadvantages of VIC (NCP2P, p. 4)
          Advantages
    Disadvantages
          *• Eliminates or reduces solvent
          * Has low-temperature processing
          *• Has unreacted pverspray that can be
            collected for reuse
          * Can be used on heat-sensitive substrates
   >Has limited industrial experience
   + Has a highly.complex process
   «• Requires high level of operator skill
   * Has high capital cost
                                                   80

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                                                            Chapter 6: Alternatives to Solvent-Borne Coatings
Table 27.  Advantages and Disadvantages of Unicoat Paint Technology
            (NFESC)
Advantages
                                            Disadvantages
* Contains no toxic pigments (e.g./ chromate,
,  lead)
* Reduces VOC emissions a'nd hazardous
  waste generation    ;
* Reduces paint and primer costs  ,        •
* Reduces paint weight on equipment and aircraft
*• Reduces labor costs because.one coat
  is applied  ,        •
V Reduces stripping cost due to less paint
  on workpiece       '        	•	^
                                              May not be suitable for all applications
conventional paints (in applications by the U.S.
Navy and U.S. Air Force). To avoid adverse
reactions, freshly painted wet surfaces must not
come in contact with alcohols, amines, water or'
acids. Costs for the UNICOAT system varies
depending on the specific application (NFESC).
                                          81

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82

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    Application  Techniques
     Various application methods are available to
     coat metal, the most common being spray
 painting and electrodeposition (EPAb,p. 20).   :
• Coatings also can be applied by dipping parts  into
 tanks filled with paint and then allowing the excess
 paint to drain off, or by direct application methods
 such as roller coating and flow coating. This
 chapter provides information on: conventional air-
 spray guns; high-volume/low-pressure spray
 guns;'airless spray guns; electrostatic spray guns;
 electrodeposition; roll coating; flow coating; and
 plural component systems. Which paint applica-
 tion process is chosen depends on the type of
 substrate to be coated, the type of coating, and the
 size and shape of the surface (IHWRIC, p..35).

 General Description

 of Spray Systems

 Paints and coatings can be applied to surfaces in a
 number of ways. Industrial coatings often  are
 applied on a production line using spray applica-
 tion techniques. Curing is done usually by an
 accelerated curing operation involving heat,
 surface catalysts or radiation (EPA, p. 15 5-156).

 In general, spray methods use specially designed
 guns to atomize paint into a fine spray. For
 industrial applications, the paint is typically
 contained in a pressure vessel and fed to the  spray
 , gun using compressed air. Traditionally, hand-held
  or automated guns (mounted on a mechanical-
  control arm) have been used to apply liquid paints
 • to metal substrates.        •                .

 .Although spray systems are easy to operate and
 - have low equipment costs, they have a certain
  amount of overspray and rebound from the  .
  sprayed surface and, therefore, are unable to
  transfer a substantial portion of the paint to the
  part (Freeman, p. 710). Spray booths with an
  open front and exhaust at the rear are generally
  used to remove the overspray as.it is generated
  (EPA,p. 155).  '
   P2 Tips for Coatings Application

   •* Eliminate the need to paint by using
     surface-free-coatings materials
   * Substitute low-VOC paints for solvent-
     borne paints
   *• Increase transfer efficiency
   * Train operators to practice proper spray
     painting techniques          .<-•   '
   > Improve housekeeping, maintenance and
     operating practices
   • Use a paint heater to adjust viscosity
   * Set application standards
  Pollution  Problem

  During conventional spray painting, some of the
  paint is deposited on the surface being painted;
  while much of it, in the form of overspray, is
  sprayed into the air. As the paint dries, the solvent
  evaporates into the air in the form of VOCs. Often
  exhaust from paint booths is run through dry
  filters to capture the particulates. Though it can be
  run through a water scrubber that separates the
  paint from the air, scrubber water is normally
  recycled, and paint solids are concentrated in the
  scrubber sump. Wheathe sump fills with paint
  sludge, it is removed and put in drums for dis-
  posal. Paint sludge that fails the TCLP test must
  be disposed of as a hazardous waste (Higgins, p.
  118).

  General  P2  Options

  .Emissions of VOCs from coatings application can
  be significantly reduced by substituting a paint
  with a lower solvent content (e.g., high-solids,
  waterborne or powder), and by increasing transfer
  efficiency. The type of coating and the application'
  method selected can have a significant effect on
.  transfer efficiency (MnTAP, p. 2). For more
  information on alternatives to solvent-borne
  coating formulations, see chapter 6.       ^  J
                                           83

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Chapter 7: Application Techniques
Whatever type of paint and application method is
chosen, the best environmental solution may be to
redesign the product to eliminate unnecessary
coating. This is a P2 option known as surface-free
coating. Many of the resins used in alternative
paints are made from regulated chemicals, and
surface-free coating can eliminate the use of these
substances (EPA, p. 165).

A number of other P2 techniques in coating
applications also are available. For coating opera-
tions that involve manual spray application, for
example, training operators to practice proper
spray techniques is a cost-effective method for
reducing VOC emissions and other wastes. Wastes
generated during the application of paints and
coatings (as well as during surface preparation and
equipment cleaning) can also be reduced by
adopting improved housekeeping, maintenance
and operating practices. Additional P2 options
include: installing a paint heater to reduce the need
for paint thinning with solvents, and setting
application standards to avoid unnecessary
coating. Each  of these options is discussed below.

Transfer  Efficiency  and  Paint
Application

Improvements in transfer efficiency can lead to
 less paint waste and lower emissions of VO.Cs.
Transfer efficiency depends on a large number of
 parameters. Some of these parameters are under
 the control of the operator, while others are not.
 Important parameters that should be considered
 when optimizing spray gun application include:

 * Spray application technique.

 * Target configuration and size. Higher transfer
   efficiency rates are easier to obtain on large
   flat objects than on small complex parts.

 * Spray booth configuration. Stray crossdrafts
   and downdrafts may reduce transfer efficiency
   by deflecting the paint away from the target.
   Temperature control and humidity control in a
   facility can significantly affect the transfer
   efficiency of electrostatic systems.

  ^•Paint characteristics.

  + Paint/airflow rates. Spray guns are designed
   to operate at maximum optimum flow rates.
  Exceeding these flow rates can reduce
  transfer efficiency by increasing the amount
  of blowback (paint bouncing off part) and
  overshoot. Excessive air pressure can also
  lead to premature drying of the paint before it
  reaches the target (paint fog).

* Spray gun distance from part. When the gun is
  placed too close to the part, bounceback
  increases and can result in poor finish quality
  (i.e., sags and runs). Too much distance results
  in overshoot and paint fog.

> Operator error (Jacobs, p. 7-8).

By definition, transfer efficiency is the amount of
paint solids deposited on an object, divided by the
amount of paint solids sprayed at the object,
multiplied by 100%. The definition of transfer
efficiency does omit some related factors for
optimum material use. Minimizing waste is not
necessarily achieved by simply using the applica-
tion technique that has the highest rated transfer
efficiency. "Real" transfer efficiency depends on a
number o'f other factors including:

+ Quality of finish. The quality of the finish
   generally improves as the size of spray par-
   ticles is reduced. Unfortunately, as the size of
   spray particles decreases, transfer efficiency
   also decreases. Some of the finest particle
   sizes are achieved with conventional LVHP air
   spray; however, this is the least efficient means
   of applying paint. To meet finish requirements,
   a compromise must be reached between'
   transfer efficiency and quality.

 * Production rate. A desired production rate
   shpuld be established before determining the
  - transfer efficiency of the coating system,
   especially if coating is being done on a
   conveyorized system that includes other
   operations. This is because the efficiency of
   spray devices will vary with the rate of applica-
   tion.

  > Desired film thickness. To determine real
    transfer efficiency, the thickness of the applied
    film versus the thickness desired should be
    established. For example, if a l-mi,l-thickfilm is
    specified, but the spray method can only
    deliver a quality film of 2 mils or greater, then
    at least 50% of the paint is wasted. Even if all
                                              84

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                                                                      Chapter-7; Application Techniques
  of the paint used is applied to the workpiece,
;  the real transfer efficiency is only 50%.

* Uniformity of applied film thickness. Aflat, fan-
  shaped spray.pattern can hold film thickness
  variations to within 1 0% of the ideal in a well-
  engineered painting system. However, a round
  doughnut-shaped pattern is used in some   .
  spray systems. This type of pattern delivers a -
  film thickness variation ©{approximately 1 mil.
  In other words, if the desired film thickness is T
  mil, the coating can have areas that are 2 mils
  thick. Even when all-the paint is applied, 25%
  is wasted. Therefore, at best the real transfer   •
  efficiency is 75%.

>Edge buildup. In electrostatic painting, edges
  .of parts can attract paint spray that would    •
   normally pass by the workpiece. Paint builds
   up oh the edges, which represents wasted
   paint even though the point is transferred to '
   the workpiece. This buildup may have to be
   sanded down and the edges may have to be
   touched up manually.        •     .

;+• Need for manual touchup/Faraday cage
   effects (in electrostatic spraying). In addition, in
   electrostatic painting, the electrostatic field
   force can prevent paintparticles from reaching
   recessed areas. To coat these areas com-
   pletely, overpainting or manual touchup of the
   nonrecessed areas often is required. In this
   situation, real transfer efficiency is less than the
   quoted transfer efficiency.

 In summary, real transfer efficiency depends on
 the particular coating situation. Replacing a system
 (manual or automatic) will not reduce VOC
' 'emissions by improving transfer efficiency alone,
 hence another step must be taken to use less
 paint. This may require changing the flow rates,
 triggering times, and/or spray tip sizes. For
 instance, electrostatic can be added to increase
 transfer efficiency, but if nothing else is changed,
 VOC emissions will stay the same and paint   •
 thickness on the part will increase. A study by the
  Research Triangle Institute found that real transfer
  efficiency depends heavily on solids content, wet
  film thickness, application equipment and operator
  experience. Therefore, if a firm is considering a
  change in paint application methods to improve
  transfer efficiency, careful testing should be done
to ensure that paint and solvent waste are truly
being minimizejd. When comparing application
techniques for possible use in a particular plant,
• spray efficiency and the above factors should all
be considered (VT DEC)!

Strategies to  Improve

Transfer Efficiency

Following are methods that facilities can use to
increase their transfer efficiencies:

•* Stand closer to the workpiece. A typical gun-
   target distqnce is 8 to 12 inches. In general, as
   the distqnce increases, transfer efficiency
   diminishes. As the distance decreases, how-
,  ever/the operator needs to reduce the fluid
   and/or air pressure to avoid applying too
   much coating to the part.                  '

^'Optimize fan size. The operator must appro-  •
   priately size the fan for the workpiece on a
 •  regular basis. A spray painter uses a fan size
   of 6 to 8 inches .when paintirig small- or
   narrow-shaped parts such as metal tubing or
   angle brackets. Adjusting fan  size is not  a
   major problem for operators who work  on
   production lines that coat one type of part or
   work in long production runs.  For those
   facilities whose parts continuously change size,
   the most practical strategy is to purchase a cap
   that the operator can change  quickly and
   easily. Because not all spray guns can be fitted,
  . with adjustable caps, facilities may need to
   contact a variety of vendors to locate this
   equipment.

 •O Reduce atomizing air pressure (where appli-
   cable). In HVLP, conventional  air atomizing,
   arid electrostatic'guns reduce air pressure to
   the lowest possible levels, which results  in
   marked improvements in transfer efficiency .
   rates. For airless', and in some cases, air-
   assisted airless guns, using a  smaller orifice
   can achieve the same atomizing results.

  * Reduce fluid pressure. If the fluid pressure and
   corresponding fluid flow rate are high,  the
   stream of paint emerging from the spray gun
   travels a relatively long distance before .
   bending and fajling to.the ground. Such a flow
  • rate has a very short residence time within the
                                              85

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Chapter 7: Application Techniques •
  spray gun and requires a large amount of
  energy for atomization. As fluid pressure
  decreases, the stream emerging from the
  spray gun shortens and less energy is needed
  for atamization. Longer residence times lead to
  more efficient atomization, which in turn leads
  to higher transfer efficiencies.
  Many spray painters argue that lowering fluid
  delivery rates slows down production speed
  and raises the cost of painting. This argument
  is true only for a very small percentage of
  facilities that have already optimized their fluid
  delivery rates. At most facilities, fluid delivery
  rates are considerably higher than the job
  requires.

+ Space workpieces closer together. Many
 • facilities that use conveyor systems suspend
  parts on hooks that are spaced 18 to 24
  inches apart. This spacing is appropriate for
  medium or large parts but reduces transfer
  efficiency on small parts. Facilities should try to
  use hooks and racks specifically designed for
  the parts they are coating. This will result in
  increased transfer efficiency and an optimized
  speed for the process line.

  Operators, however, cannot always work well
  with close spacing. For instance, parts with
  complex geometries often require the operator
  to access .the part at a variety of angles to
  ensure the quality of the coating. Also, when
  using electrostatic spray guns, painters must
  "provide sufficient spacing to allow for some
  wrap to take place.

 + Reduce air turbulence in spray booth. Paint
  facilities that use several spray booths that all
  pull from one air make-up system may experi-
  ence violently turbulent air velocities that
  change direction from one second to the next.
   Correcting this problem can be difficult and
   often requires air conditioning and airventila- •
  ' tion consultants. While this remedy can be
   costly, having a uniform, laminar air flow
   through a spray booth improves transfer
   efficiency and significantly reduces overspray
   and booth maintenance.

  * Reduce the air velocity in the spray booth (not
   below  recommended OSHA limits). OSHA
  requires a minimum air velocity of 1 00 to
  120 feet per minute through spray booths in
  which .operators use manual spray guns (the
  automated electrostatic gun's minimum air
  velocity is 60 feet per minute). Many paint
  facilities inadvertently run their booths at
  velocities well above the limit because they
 • are unaware of the effect this can' have on
  transfer efficiency. Lower air velocities  are
  especially important in  electrostatic opera-
  tions because too high a velocity can prevent
  the coating from wrapping the parts,

 * Reduce leading  and trailing edges. In cases
  where a high-quality finish  is required, trailing
  edges are needed to ensure that there  are no
  fat edges. In many cases, however, operators
 ' set the spray guns so that they trigger .sooner
  than is necessary, and/or cease too long after
  the part has passed. When painting small- or
  medium-sized parts, even a small decrease in  .
  leading and trailing edges results in significant
  improvements in transfer efficiency.

. •* Select the most efficient spray gun for the
  • intended application. Selecting a spray gun
  that meets finish requirements and has the
  highest transfer efficiency is important in
  optimizing the efficiency of a coating system.

 Before deciding whether an operation can improve
 transfer efficiency, determine the current transfer
 efficiency rates. Appendix G provides information
 on how to estimate current transfer efficiency
 (EPAq,p.74-76).

 Table 28 provides an overview of the relative
 costs and'benefits of the different spray applica-
 tion methods relative to conventional air spray
 guns.   .,

 Set  Application   Standards

 The monitoring of applied film thickness is critical
 . to ensure that a uniform and consistent coating of
 paint is being applied. Too thin a coat will result in
 premature failure in the field, while too thick a
 coat represents excess cost and waste. Other
 standards that should be established include the
 levels of Crosshatch adhesion, film hardness and
 solvent resistance. Specification of and adherence
 to'standards can do much to  minimize the level of
                                              86

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                                                                      Chapter 7: Application Techniques*
Table 28.  Cost/Benefit Summary for Spray Application Methods
Method of
Application
HVLP Spray
Air-Assisted
Airless Spray
Electrostatic
Spray
Powder
Coating
Capital Cost
Low
Low
Medium
Medium
Process
Complexity
Low
Low
Medium
Medium
Waste and
Emissions
.Medium/High
Medium/High
Medium
Low
Additional
Considerations


Only conductive parts
can be painted
Extensive parts' wash-
ing and a curing oven
are required > •
 NOTE: Capital cost refers to the cost of the system in comparison to conventional air spray. The higher the process complexity, thefiigher
 the associated costs (i.e., training for employees-and maintenance)             ;                •         ••
 rejects and ease troubleshooting when problems
 arise (Freeman, p. 487). Different tests have been -
 used over the years for liquid arid cured paints. A
 consistent system should be used for evaluating
 coating properties. The American Society for
 Testing Materials (A§TM) standards has devel-
 oped many useful standards; see appendix'E for
 more information (KSBEAP, p. 25).    •

 Adopt  Proper  Manual- Spray
 Techniques

 Untrained and hurried workers using poorly
 maintained equipment can contribute to the need
' to rework products and to clean up and dispose of
 wasted coatings, thereby increasing costs. A well-
 trained operator is far more important than the
 type of gun used. By training operators on proper
 equipment setup, application techniques and
 maintenance, companies can reduce the use of
 materials by 20 to 40% (Callahan). These savings
 will depend on the parts coated, material sprayed,
 and operator technique and experience level
 (MnTAPd, p. 6). The fundamentals of effective
 spray technique that o'peratprs can follow are:

 * Proper gun setup. Use the paint gun :
   manufacturer's suggested air cap and fluid tip
 ;  combination for the viscosity of the product
   being sprayed. Check the spray gun to see that
   it produces a proper spray pattern, and keep '
  the air and fluid pressures at the lowest  -  .
  possible settings.                  ,

•* Spray distance and angle. Keep the distance
  between the gun and the part being sprayed
 , as close as possible to the manufacturer's
  recommendations at all times (e.g.,.6 to 8
  inches for conventional spraying, 12 to  15
  inches for airless spraying, and 1 0 to 12,
  inches for'electrostatfc spraying). Move the
  spray gun  parallel to the. work, keeping  the
  gun at a right angle.    '     , '_

^Triggering and overlap. Overlap each succes-
  sive stroke (e.g.•, 50% for conventional spray-
  ing or 25% for airless spraying), using a
  Crosshatch overlap when required. Trigger the
v  spray gun at the beginning and end of each
  stroke, making sure that the gun is in motion
  before triggering. In so doing, operators can   .
  minimize the lead (i.e., the distance between
  where the gun is triggered and the point where
  the gun pattern hits the part) and the lag (i.e.,
  the distance between the point where the
  pattern leaves the part and the point where the
  gun is untriggered), thereby reducing
  overspray (Binb and iWRC, p. 2-8),

 Whenever helping companies adjust the spray
 technique of operators, technical assistance
 providers should keep in mind that, over a period
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Chapter 7: Application Techniques
of time, the firm may have selected a coating and
application equipment to conform to an incorrect
technique. Equipment settings and materials might
need to be changed to conform to an improved
technique (De Vilbiss).

Improve Current Operating
Practices

Improving operating practices is another cost-
effective pollution prevention method for reducing
the amount of wastes generated. The following
methods require minimal capital outlays, and can
be very effective (KSBEAP, p. 21):
*• Segregate waste streams to prevent mixing of
  hazardous and nonhazardous waste
•* Perform preventative maintenance for quality
  control of finishes
*• Improve materials handling and storage to
  dvoid spills
*• Practice emergency preparedness to minimize
  loss during accidents
* Schedule jobs to maximize color runs
* Implement strict inventory control by purchas-
  ing only the amount of paint required
* Standardize paints and colors to minimize the
  number of different types of paint used
* Return expired materials to suppliers for
  reblending (KSBEAR p. 21, EPAc, p. 84-85
  and Freeman, p. 487-489)
The following sections provide more detailed
information on specific application equipment and
on methods to optimize their performance.

Conventional Air
Spray (LVHP)


General Description

Conventional air spray technology, which has
been the standard for the past 40 years, uses a
specially designeii gun and air at high pressures
(i.e., 40 to 90 psi) to atomize a liquid stream of
paint into a fine spray. This technology is known
as low-volume/high-pressure (LVHP) but is
commonly referred to as conventional air spray.
Air is usually supplied to the LVHP gun by an air
compressor, and paint is supplied via a pressure
feed system (siphon and gravity systems are also
used). A typical picture of an air spray gun
features clouds of overspray around the part.

Conventional air spray produces a smooth finish,
and can be used on many surfaces. It offers the
best control of spray pattern and the best degree
of atomization. This system produces the finest
atomization and, therefore, the finest finishes. It
also sprays the widest range of coating materials
(CAGE). However, this technology produces a
great deal of overspray, resulting in low transfer
efficiencies (i.e., 30 to 60%) and uses large
amounts of compressed air (7 to 35 cfm at 100
psi). In addition, because the solvent in the paint is
highly atomized along with the paint solids,
transfer efficiency is low and VOC emissions are
high(MnTAP,p.3).

The essential components of an air atomizing
system are gun body, fluid inlet, fluid nozzle, fluid
needle assembly, fluid control assembly, air inlet,
air nozzle, air valve, fan control and trigger. Other
parts of the spray coating system may include a
compressed air supply, fluid supply and paint
heater. Recirculation booths are often used with
these systems. These booths are designed to    ,
reduce process exhaust volumes while maintaining
minimum ventilation flow rates in order to lower
operating costs for both emission control systems
and the facility in general (e.g., heating, ventilation
and air conditioning). These systems have built-in
safety limits that are based on the concentration of
hazardous constituents present in the recirculated
stream.

Advantages and  Disadvantages

The main advantages of conventional air spray
systems are the high level of control that the
operator has of the gun and the versatility of the
systems. Disadvantages of this system include
high air emissions, low transfer efficiencies and
high compressed air use. However, using proper
training and setting the gun at low pressure (20
psi), transfer rates similar to HVLP can be
achieved (Eck).

Costs

The capital investment for a new conventional air
spray system that includes spray gun, two-gallon
pressure pot, hoses and fittings can range from
$500 to $1,500.
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                                                                 Chapter 7: Application Techniques
Safety
Painters are required to wear respirators to
prevent inhalation of overspray, hazardous vapors
and toxic fumes. Depending on the noise level in •
the spray booth, ear protection may also be
required.          .                •

Alternative  Methods

There are a number of alternative spray gun
systems, including high-volume/low-pressure
(HVLP) air spray, airless spray, and electrostatic
spray. There are also variations on each of these
techniques. Of the many available methods,
electrostatic air-assisted airless spray is considered
to have the best'transfer efficiency (IWRCb, p.
39). Other available paint application methods
include electrodeposition, and dip, roll and flow
coating.                 ,.--•'

High-Volume/Low-
Pressure (HVLP) Air

Spray

General  Description
As the name suggests, this technology uses a high-
volume of air at low pressures (i.e., 0.1 to 10 psi)
to atomize paint. This technology reduces
 overspray and improves.transfer efficiency. HVLP
 guns have nozzles with larger diameter openings
 than LVHP guns for atomizing air. They can be
 bleeder (i.e., controls only the fluid flow to the
 gun) or non-bleeder (i.e., controls air flow and

 Figure 5.  HVLP System (VT DEC)

               Spray Gun
 fluid flow to the gun by use ofa trigger) types,
 and may require airflows of 10 to 30 cubic feet
 per minute. Air can be supplied to the sprayer by
 turbine air blowers or conventional shop compres-
 sors (KSBEAP, 13). Typical transfer efficiencies  ,
 with HVLP systems are 65 to 75%. Figure 5
 shows a typical configuration for a HVLP system. •

 Advantages  and  Disadvantages

 An HVLP gun is portable and easy to clean, and
 has a lower risk of blowback to the worker. In
 many cases, HVLP guns are mandated to comply
 with state air regulations (KSBEAP, p. 14).
~ However, the atomization of HVLP guns might
 not be good enough for fine finishes, and produc-
 tion rates might not be as high as with conven-
 tional LVHP spray. Generally, fluid delivery rates
 of up to 10  ounces per minute with low viscosity
 paints work best with HVLP guns (MnTAP, p, 3).
 For more information on other advantages and
 disadvantages of HVL'P, see table 29.

 Types of HVLP Systems

 Several different configurations of HVLP systems
 are available. The specific air supply (i.e., turbine
 or compressor) and fluid delivery system (de-
 scribed below) will affect the efficiency, ease of
 use, cost and versatility of the particular system
 (KSBEAP, p. 13).         :      .       -

 In a siphon-fed system,  air pressure to the
 sprayer is used to pull paint from a cup located
 below the gun, producing a fully atomized pattern
 for even surface coverage. The simple design of
                                                           Extractor
                                                       Turbine
                                                                  Motor
                                 Pressure Tank
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Chapter 7: Application Techniques
siphon-fed guns.has made it possible to buy
conversion kits for conventional siphon sprayers,
making HVLP technology very affordable for
small shop owners (KSBEAP, p. 13).

Gravity-fed systems are well adapted to high
viscosity paints such as clears, water-based paints,
high-solids paints and epoxy primers because of
the design of the system. The cup, located on top
of the gun, allows paint to completely drain,
minimizing paint waste (KSBEAP, p. 13).

The pressure assist cup system uses a cup that is
mounted beneath the gun with a separately
regulated air line to feed paint to the gun. This
design increases transfer efficiency and makes it
possible for the operator to spray evenly while the
gun is inverted, offering maximum flexibility in
application techniques (KSBEAP, p. 13-14).

Although covering every aspect of equipment
selection is not possible in this manual, see
appendix D for a list of some of the more impor-
tant points to consider when evaluating HVLP
spray equipment.

Cost and Implementation Issues

HVLP paint spray systems can be used in a
variety of painting applications. The finer atomiza-
tion of HVLP systems produce smoother finishes.
There are many paint gun models with a variety
of tip sizes to accommodate most coatings includ-
ing solvent-based paints, water-based coatings,
fine finish metallic, high-solids polyurethane,
contact adhesives, varnish, top coats, lacquer,
enamel primer, latex primer, epoxy and vinyl
fluids. The efficiency of these systems is greatly   •
reduced if the painting is done in an exposed area.

LVHP systems can be easily converted to HVLP
by retrofitting the air gun and installing the appro-
priate diameter air hoses (5/16 in. I.D.); however,
the air supply system must be able to deliver 10 to
30 cubic feet per minute of airflow at 10 psi or
lower. If a firm has a large investment in high-
pressure air compressors, conversion air systems
(CAS) can be used. The CAS reduces high-
pressure compressed air in two ways: 1) by using
an air-restricted HVLP gun that is specially ',
equipped to restrict air pressure within the gun
body, and 2) by using a small air conversion unit
that takes in high-pressure compressed air and
restricts its flow, delivering low-pressure air to the
HVLP gun (CC and Binksd). Costs can vary
depending on specific applications, painting/
coating type, paint volume, workpiece specifica-
tions and technique. Generally, costs for HVLP
paint-spray system equipment range from $500 to
$ 1,500 for a gun, hose and paint pot.

 Safety

Painters are required to wear respirators to
prevent inhalation of overspray, hazardous vapors
 and toxic fumes when using HVLP equipment.
 Depending on the noise level in the spray booth,
 ear protection may also be required.
 Table 29.  Advantages and Disadvanfages of HVLP Spray Guns (NCP2P, p. 5.)
 Advantages
Disadvantages
   Reduces overspray
   Increases transfer efficiency
 * Reduces paint waste
   Lowers booth cleanup costs
   Reduces filter replacement costs
 * Decreases waterwash reservoir treatment costs
 * Reduces VOC and HAP emissions
 •* Is portable'and easy to clean
 *• Sprays well into recesses and cavities
 «• Reduces worker exposure to blowback	
  Has atomization that may not be sufficient for
  fine finishes
  May not be able to operate with high
  production rates
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                                                                  Chapter 7: Application Techniques
  CASE STUDY:
  Lily Company

  Lily.Company Drum Reconditioning in
  Thomasville, North Carolina has experienced
  a 38% reduction in lacquer paint ysage by
  switching to HVLP guns. Converting to HVLP
  has sayed the company approximately
  $3,500 a month in materials and reduced
  paint booth cleanup. The cost of the HVLP  .
  equipment was the same as it would have
  been to purchase conventional spray gun
  equipment (VT DEC).	\	
 Low-Pressure/
 Low-Volume

 General Description

 tow-pressure/low-volume paint spraying, which is
 similar to air^assisted airless, is a relatively new
.development. Paint and air separately exit through
 the spray nozzle into a secondary fluid tip assem-
 bly. The exiting paint stream is of low pressure
 (less than 100 psig), flattened by the spray nozzle,
 but unatomized. Atomization occurs by impinging
• low amounts of compressed air (5-35 psig) from :
 two small holes in the fluid tip assembly into the
 flattened paint stream. Table 30 presents an
 overview of the advantages and disadvantages of
 LPLV Systems.                    ,
Airless  Spray

General  Description

Airless spray does not use compressed air. In-
stead, paint is pumped at increased fluid pressures
(500 to 6,500 psi) through a small opening at the
tip of the spray gun to achieve atomization".
Pressure is generally supplied to the gun by an air-
driven reciprocating fluid pump (KSBEAP, p. 16).
When the pressurized paint enters the low pres-
sure region in front of the gun, the sudden drop in
pressure causes the paint to atomize. Airless
systems are most widely used by painting contrac-
tors and maintenance painters (Binksc).

Advantages and  Disadvantages

Airless spraying has several distinct advantages
over air spray methods. This method is more
efficient than the air spray because the airless
spray is softer and less turbulent, thus less paint is
lost in bounce back. The droplets formed are
generally larger than conventional spray guns and
produce a heavier paint coat in a single pass. This
system is also mpre portable. Production rates are
nearly double^ and transfer efficiencies are usually
greater (65 to 70%). Other advantages include the
ability to utilize high-viscosity coatings (without
thinning with solvents) and its ability to have good
penetration in recessed areas of a workpiece.
  Table 30.  Advantages and Disadvantages of LPLV Spray Guns (Jacobs,
              P-15)
  Advantages
 Disadvantages
  * Reduces overspray
  * Increases transfer efficiency
  * Reduces paint waste
  * Lowers booth cleanup costs
  > Reduces filter replacement costs
  + Decreases waterwash reservoir treatment costs
  4 Reduces VOC and HAP emissions
  * Sprays well into recesses and cavities
  * Has moderate capital cost
  * Low operating costs
   Does not have a proven track record
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Chapter 7: Application Techniques
The major disadvantage of the airless spray is
that the quality of the applied coating is not as
good as conventional coatings, unless a thicker
coating is required. Airless spray is limited to
painting large areas and requires a different
nozzle on the spray gun to change spray patterns.
In addition, the nozzle tends to clog and can be
dangerous to use or clean because of the high
pressures involved (IHWRICb). For more
information on other advantages and disadvan-
tages of airless spray, see table 31.

Application  Considerations

Small fluid nozzle orifices limit the coating
materials that can be sprayed with airless sys-
tems to those that are finely ground. This rules
out fiber-filled and heavily pigmented materials.
In addition, airless spraying lacks the feather
capability that air guns have. This can result in
flooding of the surface and sags or runs if gun
movement is too slow. The high pressures used
with airless spray deliver a high rate of paint flow
through the nozzle, tending to enlarge the orifice,
increase flow rates and change spray pattern
characteristics. This is especially true at very
high pressures and with paints containing high
amounts of pigments or abrasive pigments. Strict
•maintenance is required for this system. Foreign
 objects in the fluid that are larger than the nozzle   ,
 tips can block or shut off the system. Equipment
 maintenance on pumps is high .because of the
 high pressures used (CAGE).

 Economics

 The capital investment required for a new airless
 spray system consisting of an airless spray gun,
 carted mount pump, hoses, and fittings, can range
 from $3,500 to $7,500.

 Safety

 The high velocity of the fluid stream and spray
 pattern as it exits the gun and hose is a potential
 hazard. Operators should never allow any part of
 their body to come into contact with this high-
 pressure material. Failure to keep several inches
 away from the coating as it exits the gun will result
  in serious injury. As with other spray systems,
  respirators are required, and hearing protection
  may be required as well.
Types of  Airless  Systems

Air-assisted airless systems are a variation of
airless spraying. These systems use supplemental
air jets to guide the paint spray and to boost the
level of atomization. Approximately 150 to 800 psi
of fluid pressure and 5 to 30 psi of air pressure are
used. Air-assisted airless spray systems atomize
paint well, although not as well as air spray
methods. The use of air-assisted airless systems
improves the quality of the finish, presumably
because finer paint particles are formed. The
transfer efficiency of the airless, air-assisted spray
gun is greater in comparison to airless, and with
proper operator training, the manufacturer can
obtain finishes comparable to conventional guns
(Batelle, p. III-5). This system has the same
dangers as airless spraying, but it also requires
more maintenance and operator training and has a
higher capital cost (IHWRICb).

The major difference in gun construction between
an air-assisted airless gun  and an air-atomized gun
is found in the atomizing tip. The air-atomized tip
incorporates a fluid nozzle and an air nozzle. The
fluid orifice in the center of the tip is surrounded
by a concentric atomizing ring of air. The air-
 assisted tip delivers a flat fan spray of partially
 atomized paint. Jets of atomizing air, exiting from
 ports in small projections on each side of the tip
 impacts at a 90 degree angle into the spray. The
 air jets break up the large droplets and complete
 the atomization, assisting the airless spray process.

 Economics
  The capital investment required for a new air-
 assisted airless spray system, including an air-
 assisted airless spray guri, 10:1 ratio carted mount
 pump, hoses and fittings, can range from $2,500
 to $5,000.

 Advantages

  * Low equipment maintenance. The reduced
    fluid pressures in comparison with airless spray
    cut down on pump and fluid nozzle wear.

  *Good atomization. The atomization quality of
    an air-assisted airless gun is rated as superior
    compared to an airless gun but it is not nearly
    as good as with an .air-atomized  gun.
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                                                                     Chapter 7: Application Techniques
* Low bpunceback. The extremely low atomiz-
  ing air pressure allows air-assisted airless.
  guns to spray into.corners and hard-to-reach
  areas better than with air-atomized spray.

* Varied fluid delivery. The" paint flow rates can
  ' vary considerably from about 5 to 50 ounces '
,  'perminute.   .         ...            ,

+ High'paint transfer efficiency. With a low-end
  delivery rate of 5 ounces per minute versus 25
 /ounces for airless, air-assisted transfer effi-
  ciency is even higher than airless.   •

' Table 31 presents an overview of the advantages
and disadvantages of airless spray systems.

Air and air-assisted electrostatic spray guns
 resemble nonelectrpstatic guns. An electrostatic
 gun has a wire charging electrode positioned in
 front to ionize the air. The ionized air passes its
 qharge to the paint particles exiting the gun. Some
 guns have no external electrode. Instead, an
 internal electrode located inside the gun barrel is
 used to charge the paint. In another variation, a
 metal electrode is situated in the paint tank, and
 the paint is delivered to the gun already charged.

 Cost  and  Implementation Issues

 LVHP systems cannot be converted to airless
 systems. Therefore, the capital cost for imple-
  menting airless spray is usually high. However,
  this cost might be offset by the number of advan-
  tages that airless spray provides.
 Electrostatic  Spray

 General  Description

 This spray method is based on the principle that
 negatively charged objects are attracted to-pqsi-
, lively charged objects. Atomized paint droplets are
 charged at the tip of the spray gun by a charged
.. electrode;:the electrode runs 30 to 140 kV through
 the paint at 0 to 225 microamperes (CAGE). Pairit
 can be atomized using conventional air, airless, or
 rotary systems. The electrical force needed to
 guide paint particles to the workpiece is 8,000 to  .
 10,000 volts per inch of .air between the gun and
 its workpiece. The part to be painted, which is
 attached to a grounded conveyor, is electrically
 neutral, and the charged paint droplets are at-
 tracted to that part. If the charge difference is
 strong enough,  the paint particles normally fly
 past the part and reverse direction, coating the
 edges and.back of the part. This effect is called
 "wraparound" and increases transfer efficiency
 (KSBEAP, p. L5). Electrostatic spray is used by
 most appliance manufacturers (Binksc).

 Advantages and  Disadvantages

 The major advantage of using electrostatic
 spraying is that it saves in material costs and labor.
 The labor savings is often associated with a
 changeover to automated lines, although labqr
 savings for cleanup is significantly reduced in
 either automated or manual lines. Another benefit
 of electrostatic is its ability to completely cover an
 object with a uniform thickness, including areas
 that are normally inaccessible (Batelle, p. Ill-10).
   Table 31. Advantages and Disadvantages of Airless Spray Systems (NCP2P,
               p. 5)
   Advantages
   Disadvantages
   * Has high rates of "paint flow
   *Has relatively high transfer efficiency
   * Has versatile gun handling (no air-hose)
   * Has ability to apply highly viscous fluids
   * Has relatively poor atornizatiori  .
   * Has an expensive nozzle
   *• Reduces fan pattern control
   > Has coatings limitations
   + Has a tendency for tip plugging
   •* Has a skin injection danger
   <> Requires increased operator training
   * Requires increased maintenance
                                              93

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Chapter 7: Application Techniques
The initial capital investment for electrostatic
systems is high (EPA, p. 155). In addition;
electrostatic systems must be properly grounded at
all stages of paint delivery in order to reduce
injuries and fire hazards that can result from
shorting or sparking (KSBEAP, p. 15-16). An-
other problem with electrostatic spray is that the
paint is attracted to all grounded objects, including
the conveyor and conveyor protection systems in
assembly line painting, the paint booth ceiling, the
spray gun and the spray gun handler. Work has
been done on developing an electrically charged
paint repelling panel to protect against stray paint.
Such repelling panels are not 100% effective, but
they can cut down on problems from stray paint
(IHWRICb). For more information on other
advantages/disadvantages of electrostatic spray,
see table 32.

Types  of  Electrostatic  Systems

Rotary atomization is a variation of electrostatic
spraying that uses centrifugal force generated by
discs or bells to atomize paint, which drives it
from the nozzle. The atomization of this method
is excellent as is the transfer efficiency. This
method also can be used with paints of different
viscosity. However, the equipment needed for this
type of application is very specialized and usually
requires a major conversion of a painting line
(IHWRICb). Typical costs for a new rotary
atomization system consisting of a rotary atom-
 izer, 2-gallon pressure-pot, and hoses and fittings
 may range from $5,000 to $7,500 .

 Implementation  Issues

 An LVHP air spray system can be converted to an
 electrostatic system. In most cases, however,
 airless, air-assisted airless, or rotary atomization is
 used with electrostatic spray. This is because
 LVHP air-afomized electrostatic spray has a
 transfer efficiency of only 60 to 70%. Airless,
 however, runs from 70 to 95%, and rotary runs
 from  80 to 90% (IHWRICb).

 Part and gun cleanliness are essential for efficient
 electrostatic operation. Dirt or oversprayed paint
 can form on a conductive track on the plastic gun
 tip and short out the system. For top efficiency,  '
 the part to be coated should be the closest
 grounded object to the charging needle on the
 spray gun. The charged paint particles are at-
tracted to the nearest electrically grounded item;
the larger the item, the greater the attraction.

Ungrounded objects in the vicinity of the charged
gun electrode can pick up a considerable electrical
charge. The charge buildup can arc over or spark
if a grounded object is brought near. The intense
heat of the arc may be sufficient to ignite the   .
solvent-laden atmosphere typically found in a
paint booth'.

Paint buildup on hooks or hangers can act as an
insulator and block the flow of electric current in
the electrostatic circuit. Hangers and hooks should
be regularly stripped or otherwise cleaned of paint
buildup to maintain good grounding-contact
between the parts and the conveyor.

Because of high transfer efficiencies, air velocity
in spray booths may be reduced from 100 to 60
feet/minute. This results in a 40% reduction in
make-up air costs and reduces emissions.

Safety

In 1995, the National Fire Protection Association
(NFPA) rewrote the NFPA 33 Standard to require
fast-acting flame detectors for all automatic
electrostatic liquid painting applications. These are
also required for automatic electrostatic powder
coating applications. All electrically conductive
materials near the spray area such as material
supply, containers and spray equipment should be
grounded as well.

Cost
The capital investment for a new liquid electro-  .
static spray system consisting of an electrostatic
 spray gun, 2-gallon pressure pot, and hoses and
 fittings can range from $4,900 to $7,500. The
 capital investment required for a new electrostatic
 powder coating spray system, including powder
 application equipment, powder booth, cleaning
 system and bake oven, may range from $75,000
 to $1,000,000. (CAGE).                   .   '

 Other Methods

 This section presents brief descriptions of a
 variety of other paint application methods, includ-
  ing electrodeposition, various dip processes, and
                                              94

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                                                                       Chapter 7: Application Techniques
   Table 32. Advantages and Disadvantages of Electrostatic Spray Guns
                (NCP2P, p. 6)
   Advantages
Disadvantages
   '+Has high transfer efficiency
   •*Has good edge cover
   * Has good wraparound
   * Has uniform film thickness
*Has guns that tend to be bulky and delicate,
•* Requires extra cleanliness -...-.
* Creates Faraday cage effect
* Can be safety/fire hazard
^Requires all parts*to be conductive (however,/
-  special conductive precoatings on nonconductive
  workpieces can be used to permit electrostatic
  spray)          .                 •
+ Has high equipment and maintenance cost
 direct application methods such as roller and flow
 coating.

 Electrodepositipn/Electrocoating (E-coat). This
 process applies paint in a method that is similar to
 electroplating. In the E-coat process, a paint film
 from a waterborne solution is electrically depos-
 ited onto a part. Parts are usually made primarily
 of steel. An E-coat bath contains resin, pigment
 (unless it is a clearcoat), solvent (water and a
 cosolvent) and additives. The most commonly
 used resins in this process are epoxies and acryl-
 ics. These systems have no or low VOC  emissions
 and produce little toxic waste.

 . The liquid is a very dilute emulsion of waterborne
 paint. Reactions between the paint particles and
 certain bath components cause the resin to be
 ionic. The electric current causes the paint par-
 ticles to migrate to the metal surface. As more and
 more particles collect, water is squeezed out and
 cross linking of the resin particles occurs. TJie
 transfer efficiency of electrodeposition is greater
""'than 90%. High production rates are possible, and
 production can be automated. However, this  •
 method is costly and requires a lot of energy.
 Also,.employees need a high level of training to
 use this system (IHWRICc).           "...   .

 E-coat is extremely efficient, depositing a mostly
 uniform coating on all surfaces that can  be
 reached by electricity. Waterborne electrocoating
 systems may be used to apply uniform, pinhole-  '
 ' free coatings. For films that require high appear-
 ance.standards, E-coat uses acrylic resins.
 Electrocoatings are resistant to attack'by UV light
   CASE STUDY:
   Navistar International Transportation
   Corporation

   Navistar International. Transportation
   Corporation's assembly plant in Springfield,
   Ohio, is the site of painting and final assembly
   of Navistar's medium-and heavy-duty trucks
   and school bus chassis. The plant's compre-
   hensive pollution.prevention efforts have
   resulted in significant reductions in environmen-
   tal releases.       •

   Many of the'pollution prevention activities have.
   taken place in^Navistar's painting operations.
   In the prime coating operation, conventional
   air-atomized, low-solids paint was replaced
   with waterborne paint, resulting in a 50%"
   reduction in.VOC emissions. Electrostatic   •  •
   robotic application of paint has increased
   transfer efficiency of equipment in topcoat
   operations. For almost all colors of topcoat,
   Navistar was able to change from applying two
   coats of paint to only one coat of paint without
   lowering product quality, reducing the amount
   of paint wasted by 65,000 gallons and the
   amount of solvent used by 138,000 gallons
   annually.                              •     •

   Other raw material, process and equipment
   changes have resulted in annud reductions
   exceeding 65 tons of VOC emissions, 82 tons
   of HAPs and 2^600 gallons  of hazardous
   waste.    •          •                 •,

   * Savings-                    •
   Navistar reports savings in excess of $3.5
   million. (OH EPAb)
                                             95

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Chapter 7: Application Techniques
and have good weatherability. Typical applica-
tions include truck beds, engine blocks, water
coolers, microwave ovens, dryer drums, com-
pressors, furnace parts, housings for the automo-.
tive industry, shelving, washers, air conditioners,
file cabinets, switch boxes, refrigerators, trans-
mission housings, lighting fixtures, farm machin-
ery, and fasteners.

One drawback to the electrocoating system is
that it is limited to one color at a time. Each color
requires its own tank.

Autodeposition. Autodeposition is a process used
to deposit organic paint films Onto iron-, steel-,
zinc- and zinc alloy-plated substrates.
Autodeposition is typically an 6-step process,
including alkaline cleaning, rinsing with plant water
•and deionized water, autodeposition (immersion),
immersion sealing rinse and curing. The part is
immersed into a solution containing paint conv-
pounds, usually a vinyl emulsion, hydrofluoric
acid and hydrogen peroxide. When the part is
submersed, the paint compound precipitates out of
 the solution and coats the part. The part is then
 removed from the tank, rinsed and cured
 (KSBEAP,p.20).

 Autodeposition is an effective method for achiev-
 ing corrosion resistance and coverage of objects.
 Autodeposited films also provide extremely
 uniform thicknesses, typically 13 to 30 microme-
ters (0.6 to 1.2 mils). These resins also have
excellent hardness, formability and adhesion
characteristics. Two other advantages of
autodeposition are that organic solvents are not
needed, and little or no VOCs are emitted.
Autodeposited films have high transfer efficiencies
(approximately 95%), further reducing environ-
mental impacts. This system also does not have'
  CASE STUDY:
  Emerson Electronics

  In 1977, the Emerson Electronic plant in
  Murphy, North Carolina,,was faced with a
  decision concerning the type of paint line to
  install for producing a quality finish on die-
  cast aluminum, bench power tool parts.
  Emerson compared an electrostatic spray
  process for coating solvent-based paint to an
  electrocoating process applying a water-
  based paint.

  Emerson found that the electrocoating system
  offered the following advantages:
    • Lower VOC emissions, 70 pounds per day
    versus 3,040 pounds per day
    • Lower hazardous paint waste, 0 pounds
    per day versus 160 pounds per day
    > Production cost savings of $1,080,000 per
    year
    > Raw material cost savings of $600,000 per
    year                           (VT DEC)
   Table 33. Advantages and Disadvantages of E-Coat Systems (NCP2P, p.7)
   Advantages
  Disadvantages
   «• Utilizes over 90 percent of coating material
   «• Has very thick, uniform coating on all surfaces
     that can be reached by electricity
   *• Has high production rates
   I * Produces corrosion-resistant coating
   + Has low VOC and HAP emissions
   I * Can be fully automated
   •*Can apply seiond coat on uncured
     electrocodt
  * Has substrate limitation
  * Requires separate lines for each color
  * Requires high cost to install
  *• Has masking problems
  * Requires sophisticated maintenance
  * Has air-entrapment pockets
  * Has difficulty coating bulky, small parts
  * Requires corrosion-resistant equipment
  * Requires de-ionized water     .
  + Has difficulty sanding/stripping
  *• Has high energy demands
  + Is restricted to large volume finishing
  * Has coating thickness limitation
  + Requires high level of training for employees
                                              96

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                                                                     Chapter 7: Application Techniques
fire hazards. However, autodeposition produces a
dull or low gloss finish and has few available
colors (IHWRICc). The largest application for
autodeposition coatings have been for nonappeaf-
ance and under-hood parts in cars and trucks due
to their excellent anticorrosion properties.,It is also
used on drawer slides for office furniture, replac-
ing zinc-plating:                    '..•..'•

Dip Coating. With this process, parts are dipped
(usually by conveyor) into a tank of paint. Dip  '
coating allows for a high production rate and high
transfer efficiency and requires relatively little
labor. The effectiveness of dip coating depends
greatly on the viscosity of the paint, which
thickens with exposure to air unless it is. carefully.
managed. The viscosity of the paint in a dip tank
mustremain practically constant if the deposited
film quality is to remain high. To maintain viscos-
ity, solvent must be routinely added as makeup.
This results in higher VOC per gallon ratios.

Dip coating is not suitable for objects with hollows
'or cavities, and generally the finish is of lower     •
quality (IHWRICc). Color change is slow and not
 feasible for most dip operations. This process is •
 usually used to apply primers and to coat items
 whose appearance is not vitally important. Top
 coats are not commonly applied by dipping.
 Coatings applied by dipping have only a poor to
 fair appearance unless parts are rotated during
 drippage.'Dipping is well suited for automation
 with conveyerized paint lines.

 Capital investment required for dip coating is
 minimal. All that is required is a tank for the
 coating. The parts may be dipped manually, or -
 automatically with a conveyor. Given the large
 surface area of the dip tank, adequate ventilation
 must be provided to prevent buildup of fumes and
 vapors. An efficient fire-extinguishing system must.
 be installed as a safety measure if flammable
 paints are. used (CAGE).

 Flow Coating. In a flow coat system, 10 to 80
 separate streams of paint coat all surfaces of the
 parts as they are carried through the flow-coater
 on a conveyor. This system has the advantages of
 dip coating along with low installation costs and
 low maintenance requirements. The quality of the
  Table 34.  Advantages and Disadvantages of Autodeposition Systems
               (NCP2P, p. 7)
  Advantages
Disadvantages
    Has excellent anticorrosion properties
    (no phosphate coating required)
  * Wets T 00% coverage of surfaces
    (no Faraday cage areas)
    Uses waterborne material
  •» Requires no.external source of electricity
  Has dull or low gloss appearance
 • Has few colors available
  Table 35. Advantages and Disadvantages of Dip Coating Systems
               (NCP2P, p. 7)
  Advantages
Disadvantages
    Has high production rates.
    Requires low labor
    Has high transfer efficiency
    Can closely rack parts
   * Coating thickness does not depend on
    operator skill    ,         •         .
    Is well suited to automated applications
> Is extremely dependent on viscosity of the paint
V Is not suitable for items with hollows or cavities
* Has slow color change
>Can be a fire hazard
* Has poor to fair appearance
+ High VOC emissions relative to the amount
  of coating applied in low VQC applications
                                             97

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Chapter 7: Application Techniques
finish is also comparable to dip coating
(IHWRICc).

Flow coating is usually used for large or oddly
shaped parts that are difficult or impossible to dip
coat. Coatings applied by flow coating have only a
poor to fair appearance unless the parts are
rotated during drippage. Flow coating is fast and
easy, requires little space, involves relatively low
installation cost, requires low maintenance, and
has a low labor requirement. Required operator
skill is also low. Flow coating achieves a high paint
transfer efficiency, often 90% and higher (CAGE).

Principal control of dry-film thickness depends, on
the paint viscosity. If viscosity is too low, insuffi-
cient paint will be applied. If the paint viscosity
rises, extra paint will be applied. This can increase
paint costs and also plug small holes in the part
(CAGE).

Curtain Coating. Instead of the multiple streams
of paint found in flow coating, curtain coating uses
a waterfall flow of paint to coat parts on a con-
veyor belt. The paint flows at a controlled rate
from a reservoir through a wide variable slot.
Curtain coating has a high transfer efficiency and
covers parts uniform ly, but is suitable only for flat
work. The quality of the finish depends on the
viscosity of the paint (IHWRICc).
Roll Coating. Roll coating is the process of
applying a coating to a flat substrate by passing it
between rollers. Paint is applied by one or more
auxiliary rolls onto an application roll, which rolls
across the conveyed flat work. After curing, the
coated substrate is then shaped or formed into the
final shape without damaging the coating. The
paint-covered rollers have large surface areas that
contribute to heavy solvent evaporation. This can
pose a fire hazard from flammable solvents in
solvent-borne formulations.

Roll coating is divided into two types: direct and
reverse roll coating. In direct roll coating, the
applicator roll rotates in the same direction as the
substrate moves. In reverse roll coating, metal .
feed stock is fed between the rolls as a continuous.
coil. The applicator roll rotates in the opposite
direction of the substrate.

Roll coating is limited to flatwork and is extremely
viscosity dependent. Coating properties should be
checked often to ensure proper results. These
tests should include adhesion, impact resistance,
flexibility and hardness. A well-known application
of roll coating is coil coating, in which coiled metal
strip is uncoiled, pretreated, roller coated with
paint, cured and then recoiled (IHWRIC, p. 36).

Roll coaters are typically custom made for each
application. Roll coaters can be made-to-order to
  Table 36. Advantages and Disadvantages of Flow Coating Systems
               (NCP2P, p.7)
Advantages
+ Has high transfer efficiency
* Has low installation cost
* Requires little maintenance
* Has high production rates "
* Requires less labor.
Disadvantages
* Has poor to fair appearance
* Requires principal control of dry-film
thickness to control viscosity of pajnt
  Table 37.  Advantages and Disadvantages of Curtain Coating Systems
               (NCP2P, p. 7)
Advantages
*• Has high transfer efficiency
+ Enables uniform coating thickness
Disadvantages
* Is suitable only for flat work
+ls highly dependent on viscosity
                                             98

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                                                                      Chapter 7: Application Techniques
Tabte 38.  Advantages and Disadvantages of Roll Coating Systems
             (NCP2P, p. 6)
Advantages
«•' Has high transfer efficiency
> Has high production rates
Disadvantages
* Cannot paint hard-to-reach areas
••* Is limited to flat work
accommodate widths ranging from 14 to 100
inches.                        .

Plural Component Proportioning System for
Epoxy Paints. Plural component proportioning
systems are self-contained epoxy paint measuring
and mixing systems. These systems accurately
mix the epoxy paint components, produce the
precise amount of paint required by an applica-
tion, and consequently minimize waste.
             •'''..          •     •"*"
Epoxy paint mixtures are prepared by premixing a
base and a catalyst and then combining them in
appropriate proportions in a separate container.
After mixing and waiting the specified time,
application of the paint to the workpiece may
proceed. Once mixed, epoxy paints have a limited
pot-life that cannot be exceeded without affecting
the characteristics of the paint. If the pot life is
exceeded, the mixture must be disposed of, and
the application equipment must be cleaned. Under
conventional methods, these mixtures are pre-
pared by hand, a process that frequently leads to
the generation of excess paint. The solvents used
to cleanup and dispose of excess paint generates
hazardous waste consisting of spent solvents and
 waste paint.

 Plural component proportioning systems are used
 in conjunction with application devices. A typical
 proportioning and application system layout
 includes the following components: proportioning
 pump module, mix manifold, mixer, application
 device, materials supply module, and purge or
 flush module. These systems optimize painting
 'operations by maximizing efficiency and minimiz-
 ing waste generation.

 The plural component proportion system for
 epoxy paints provides for total control of materials
 from containers) to application. The system is
 accurate and can provide more consistent material
 quality than hand mixing,These systems can also
                                              keep pace with higher production requirements.
                                              The systems mix the coating on demand (i.e., as
                                              the gun is triggered); This does not result in
                                              significant quantities of waste materials because
                                              no excess paint is mixed. Material cleanup requires
                                              less labor and maintenance, and generates less
                                              waste because the mixed material can be purged
                                              with solvent from the mix manifold, mixer, hose,
                                              and applicator before it cures. The plural compo-
                                              nent system is a closed system and, as a result,
                                              there are fewer spills, less contamination or waste
                                              to cleanup, and less exposure of toxic materials to
                                              personnel.-In addition, the proportioning system
                                              makes bulk purchase of material practical.

                                              If an epoxy paint requires significant induction
                                              time (i.e., 15 minutes or longer), the plural
                                              component system can still be used, provided that
                                              the mixed paint is allowed to stand in a separate
                                              .container prior to application.

                                              Capital costs for plural component proportioning
                                              systems can range from $6,000 to $7,500 for
                                              basic units that mix two materials, up to $50,000
                                             . to $70,000 for systems that mix multiple materi-
                                              als. Application systems are an additional compo-
                                              nent, and their capital costs can range from $500
                                              to $5,000. Each application needs to be evaluated
                                               on a case-by-case basis with respect to material
                                               and labor costs and savings.

                                               Supercritical Carbon Dioxide (CQ2).
                                               Supercritical fluid spray application allows substi-
                                               tution of supercritical carbon dioxide for up to
                                               two-thirds of conventional solvents concentration
                                               in spray-applied coatings, reducing VOC emissions
                                               by 30 to 70%. The proportioning and supply
                                               system from Union Carbide (UNICARB) mixes
                                               supercritical CO2 solvent with coating concentrate
                                               and supplies the material to a specially designed
                                               spray gun (i.e., internal mixing). The CQ2 solvent
                                               is compatible with high molecular weight resins
                                               and existing painting facilities and procedures;
                                             99

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Chapter 7: Application Techniques
 Table 39. Advantages and Disadvantages of Plural Component
              Proportioning Systems (NCP2P, p. 7)
 Advantages
Disadvantages
  «• Provides total control of materials from
   container to application                •
  * Generates paint on an as-needed basis,
   eliminating the generation of excess paint
   (Under conventional methods, this excess
   paint is frequeritly disposed of as hazardous
   waste)
  *• Minimizes solvent cleanup
  * Reduces chance of spills
  *• Reduces worker exposure
  Needs to be designed for specific applications
therefore, mis-compatibility enables the use of
solvent-borne formulations with substantial VOC
reductions.

Advantages and Disadvantages

In the supercritical CO2 spray process, the sol-
vent-like properties of supercritical CO2 are  .
exploited to replace a portion of the solvent in the
conventional solvent-borne coating formulation.
The addition of supercritical CO2 acts as a diluent
solvent to thin the viscous coating just before
application, so that the coating can be atomized
and applied with a modified spray gun (EPA1).
Supercritical fluid spray application can be used to
coat metal and plastics. The applied coating has a
higher viscosity that allows thicker coatings
without runs or sags. However, care is required in
working with high-pressure gas at high operating
temperatures (100 to 150°F) (TURI, p. 2).
Cost and Implementation Issues
This system requires investment in hew equip-
ment for paint mixing, handling and spraying. In
1991, five coating formulators were licensed to
develop, manufacture and market UNICARB
systems, including Akzo (automotive components,
furniture), BASF (automotive), Guardsman
(furniture), Lilly (furniture, plastics, heavy
equipment) and PPG Industries (automotive,    >
heavy equipment) (EPAd, p. 82).


Paint Booths

A paint booth is an enclosure that directs
overspray and solvent emissions from painting  .
operations away from the painter and toward an
entrainment device. Spray booths are designed to
capture particulate matter that is released into the
air during coating operations. The'y are not
  Table 40.  Advantages and Disadvantages of Supercritical Carbon Dioxide
              (NCP2P, p. 3)
Advantages
+ Has high quality finish
*• Needs fewer coating applications
+ Reduces VOCs and HAPs
* Reduces operating costs
+ Is easy to retrofit
+ Has high transfer efficiency
* Reduces worker exposure for solvent vapors
Disadvantages
+ Has limited industrial experience
* Has lower fluid delivery rates than airless or air
spray guns
* Has bulky gun and supply tubing
* Has royalty costs '
                                          100

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                                                                      Chapter 7: Application Techniques
Table 41. Transfer Efficiencies of Various Application Technologies
             (IHWRIC> p. 37, KSBEAP, p. 23  and CC)
Technology
Conventional Air Spray
HVLP Spray
LPLV Spray
Airless Spray
Electrostatic Spray
Electrodeposition
Transfer
Efficiency
30 to 60%
50 to 90%
60 to 80%
65 to 70%
65 to 95%
90 to 99% ,
Operating
Cost
Low
Low
Low
Medium/high
Medium/high
NA
Finish
Quality
'High
High
. Unknown
Low
Low.
NA
Recess
Coverage
Good
Good
Good
Good " '
Poor
NA - •'
 NA=not applicable

abatement devices for VOCs. A spray booth's
primary function is to protect the painter and
other employees from exposure to potentially
toxic vapors and particulates. Another function of
the booth is to prevent fires within a facility by
venting high concentrations of flammable solvent
vapors out of the building (EPAq, p. 149).

Pollution Problems

Discharges from paint booths consist of particulate
matter and organic solvent vapors. Particulates
result from solids in the paint that are not trans-
 ferred t"o the part. Organic solvent vapors are from
the solvent, diluent or thinner that is used with the
 coating to reduce the viscosity of the paint. Much
 of the particulate matter is captured by a dry,
 water-wash or baffle filter (these are discussed
 belo.vv). Solvent vapors are controlled or recov-
 ered by the application of control technologies
 such as condensation, compression, absorption,
 adsorption or combustion. Solvent vapors can be
 minimized by using more efficient equipment, and
 low or no VOC materials. Increasing the transfer
 efficiency of the painting operation can result in
 both reduced particulate and solvent emissions
 (EPAq, p. 149).

 Types  of Paint  Booths

 There are two basic types of enclosures that are
 used in most painting applications: dry booths and
• wet booths. The key difference between the two
 is that a dry booth depends on a filter of paper,
 fiberglass or polystyrene to collect overspray,
 while the wet booth uses water with chemical
additives to collect overspray. The type of booth
selected can affect the volume and type of paint
wasted A third type of booth is used exclusively in
powder coating operations.                '.'•'.

Although a spray booth is generally thought of as
an enclosed.painting area, this is not always the
case. For instance, facilities that paint very large
pieces may have a booth that only has one side,
consisting of an exhaust plenum that draws
solvent and particulates away from the operator. It
 is also not uncommon to see two spray booths
 opposite one another. This set-up allows for very
 large workpieces to be transported in between the -
 booths either by a conveyor or a forklift truck that
 runs between the booths. Often neither booth has
 a ceiling, and they draw air from the surrounding
 factory (EPAq, p. 149).

 Regardless of the size or design of the booth, they
 consist of one of three basic designs for directing
, airflow.

 >Cross-draft. In a cross-draft booth, air moves.
   from behind the operator toward the dry filter  ,
   or water curtain (parallel to the floor). This type
   of booth is ideal for systems where the parts
   are moved through the facility in a rack or     ..
   conveyor system, and the painter applies the
,   coating from only one direction. However,
   these types of systems can be used if the paint
   must be applied .in more than one direction.
   This type of ventilation system is usually the
   least expensive.     .        p
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Chapter 7: Application Techniques
 Table 42. Overview of Application Technologies (IHWRIC, p. 36-37;
            IHWRICb,c; and Binksc)
Technology
HVLP Spray
LPLV Spray
Airless Spray
Air- Assisted
Airless Spray
Rotary
Atomization
Pollution
Prevention
Benefits
* Reduces overspray,
increasing transfer
efficiency
4 Reduces VOC and
HAP emissions
> Lowers risk of
blowback to the
worker
* Has a .high transfer
efficiency rate
+ Has low operating
costs
* Has moderate
capital costs
*• Has a transfer
efficiency of 65
to 70%
* Cuts overspray by
more than half,
and is cleaner and
more economical
* Has higher transfer
efficiency and lower
chance of blowback
* Has excellent
efficiency
Reported
Application
*Can be used on
many surfaces

^.Hydraulic
atomization used
most widely by
painting
contractors and
maintenance
painters
+ Heated
atomization usec
by furniture
manufacturers
and industrial
finishers
•*Used by furniture
and industrial
finishers

Operational
benefits
*ls portable and
easy to clean
^Allows'operator
to vary the air
pressure, air
volume, paint
pressure and
spray pattern

*• Is twice as fast
as air spray and
produces a
higher film build;
is more portable
than air spray
* Has material
savings that are
50% better
than air spray
*Has higher film
build per pass
than air spray
+ Can be used
with paints of
different viscosity
Limitations
•*Has production
rates that are
not as high as
conventional air
spray
*ls widely used
* Is limited to
painting large
areas, requires
a different
nozzle to change
spray patterns;
nozzle tends to
clog and can be
dangerous to use
. or clean because
of the high
pressures
involved
*Has same
dangers as
airless, but'
requires more
maintenance and
operator training,
. and has a higher
initial capital cost
* Requires high
degree of
cleanliness
, - • (continued on next page)
                                     102

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                                                           Chapter 7: Application Techniques
Table 42. Overview of Application Technologies (IHWRIC, p. 36-37;
            mWRICb,c; and Binksc) (continued)
|r











































Technology
Electrostatic
Spray












V








Auto-
deposition •
•



Electro-
deposition


t





	 ; 	 — p
Pollution
Prevention
Benefits
* Has high transfer
efficiency
* Produces little over-
spray and uses
' i ' .
relatively little paint




0 '




• ' . > •' .









* Uses water-borne
.paints



v:
* Has transfer
efficiency of more
than 90% . '









Reported
Application
* Is good for .
. painting oddly
shaped objects
* Is used by most
appliance
manufacturers







/•



,






* Is limited to iron,
steel, zinc and
zinc-alloy plated
materials



4> Is limited to
•metallic or other
electrically con-
ductive objects
(e.g., autobody
coating)




. ' ' •

Operational
Benefits
* Produces a
uniform coat
because the
paint itself acts
as an insulator


















#
«• Is effective for
anti-corrosion
properties and
coverage of the
objects
V Uses no
electricity
* Can accommo-
, date high
production rates,
production can
be automated

'v ;






Limitations
* Has limited
coverage with
complicated
' parts because
of Faraday cage
effects
+Can paint only •
conductive parts
* Presents a
possible shock
hazard
*ls limited to only
-one coat
*ls more expen-
sive^ slower and
has higher
" maintenance
costs than air
spray
* Is limited to
chargeable paints
* Surface of the
object must be
extremely clean
>ls limited to dull
or low gloss
finish'; few
available colors



* Requires that
objects be metallic
or electrically
conductive
» Is costly and
requires a lot of
eher,gy ,
* Requires that
employees receive
high level training to
use this system •
[continued .on next page)
                                       103

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Chapter 7: Application Techniques
 Table 42. Overview of Application Technologies (IHWRIC, p. 36-37;
              IHWRICb,c; and Binksc) (continued)


Technology
Dip, Flow and
Curtain
Coating











Roll Coating.






Pollution
Prevention
Benefits
* Has high transfer ,
efficiency












+ Has high transfer
efficiency






Reported
Application
* Is well suited
for parts that
are always the
same color and
have minimum
decorative finish
requirements,
such as
agricultural
equipment
-



> Is limited to sheet
materials (e.g.,
'strip metal and
boards); used to
decorate cans
and other metal'
objects

Operational
Benefits
> Has high
production rate
* Requires
relatively little
labor









+ Has high
production
rates






Limitations
* Depends
greatly on the
viscosity of the
paint, which
thickens with
exposure to air
unless. carefully
managed
Vis not suitable
for objects with
hollows or
cavaties .
*Has lower
quality finish
* Is limited to flat
work .





 •» Down-draft. Down-draft booths move air
  from the cejling of the booth vertically down-
  ward toward an exhaust plenum in the floor.
  This type of booth is preferred when the paint
•  operator must be able.to walk around the
  part, particularly in the case of painting large
  machines. These booths usually cost more than
  cross-draft booths because they require
  building' a pit beneath the booth. The operat-
  ing expenses with a down-draft are also
  usually higher because these systems draw
   more air.
 * Semidown-drdft. This type of booth moves the
   air down and then to the side where the •
   exhaust is located. Semidown-draft booths
   offer a compromise between the cross-draft
   and down-draft configurations (EPAq, p.
   149).        '     ..
Decisions about equipment should be made based
on the type and volume of painting done and the
volume of waste generated.

Choosing between a dry filter, water-wash or
baffle spray booth encompasses many different
issues. The following section provides informa-
tion on these three systems. Analysts estimate that
80% or more of the spray booths in use today are
of the dry filter type (EPAq, p. 151). Inrecent
years, however, many facilities have switched to
water-wash booths because of their lower mainte-
nance and hazardous waste costs. However, there
are other concerns with these booths. The follow.-
ing section provides more detail on dry filter and
water-wash booths.

Dry  Filter  Booths

There are many types of dry filter systems,
however, they all operate on the same principle:
                                           104

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                                                                         Chapter 7: Application Techniques
                                               i
participate- laden air flowing toward the filter  ,
medium is forced to change directions rapidly.
The particulate, having more inertia than the
surrounding air, impacts the filter medium and is
removed from the air flow. The scrubbed air is
then vented to the atmosphere.

There are four general types of filters currently
used; fiberglass cartridges, multilayer honey-
combed paper rolls or pads, accordion-pleated
paper sheets, and cloth rolls or pads. Each type of
filter has different characteristics for particulate
capacity, removal efficiency, cost and replacement
time. Filter performance is characterized by three
basic parameters: particulate capacity, resistance
to air'flow and particulate removal efficiency.
Filter replacement is required when the filter
becomes heavily laden with captured particles,
resulting in a reduction in removal efficiency and
an increase in the pressure differential across the
filter face. The primary waste stream generated
by dry booths is spent filters. When using lead or
. zinc chromate paints, the dry filter will eliminate
 5 0 to 90% of the hazardous waste generated by
 water-curtain paint booths.

 Generally, small-volume painting operations find
' that the lower cost of a dry-filter booth meets their
 requirements. This equipment requires a low
 capital investment relative to wet-booths and are
 simple in design. The filters act to remove paint in
 airborne particles by capturing them as they are  *
 forced through the filter. Ease of replacing a
 relatively low number of filters produced by small
 operations makes such an approach attractive. As
 paint volume increases, though, filter replacements
 must be made more often. This may increase
 costs for labor and materials significantly
. (Mitchell, p. 10)..                -

 Dry filters effectively remove up to 95 to 99% of
 particulates. These systems are also versatile.
 They can be used in booths of all designs (small,
 large, cross-draft, down-draft and semidown-
 draft). These booths can  also be operated for a
 variety of coating technologies, including polyure-
 thanes, epoxies and alkyds. However, they cannot
  be used for nitrocellulose paints and some
•  waterborne coatings (proper filter selection is
  critical in these cases). They are inexpensive to
  purchase, and depending on the nature of the
paint (i.e., pass or fail TCLP test), they are also
inexpensive to operate.

A disadvantage of dry filter booths is that they
are generally not appropriate for facilities with
high coating use (i.e;, greater than 5 gallons per
square foot of filter areas per day). They also
have problems with VOC emissions, since they
do  not remove VOCs.                         .

Regarding safety, dry filters are a potential fire
hazard, especially if dry overspray is allowed to
Jjuild up. Typically, the majority of this waste is
the filter media, which can be contaminated by a
relatively small amount of paint. Reusable filters
may decrease waste volume and reduce disposal  .
cost. In some applications, such as powder
coatings, overspray can be reused.         ,

Choosing the proper type of dry filter is important
for a facility's operations. Dry filter characteris-
tics that should be considered include:

* Efficiency-its ability to remove particulates
  before they enter the stack
*Resistance-this is the pressure differential that
  ensues when the high velocity of air passes
  across the filter bank
* Holding capacity-the amount of overspray that
  a filter can hold or retain during its service life
* Incineration profile-can spent filters be
  burned?
 * Biodegradability-does the product degrade
  •naturally?                   :
 * Landfill option profile-does it meet landfill
  standards?
 * Flammability-does it meet the National Fire
  •Protection Bulletin number 33 requirement and '
   Underwriter's  Laboratories Approved Class 2
   list?    .
 * Suitability for various coatings-some water-
   borne coatings may complicate filter choice; .
   facilities should check to make sure filter is
   compatible with all/coatings that will be used

 Filters made from expanded polystyrene are also
 available. Facilities can reuse these types of filters
 after carefully brushing the overspray off the
 surface with a bristle brush. Hence, the same
 filters can be used several times until they break
 or become unusable. Manufacturers have pro-
 moted the practice of dissolving the filter in a
                                               105

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Chapter 7: Application Techniques
drum of solvent and paint waste when a facility is
ready to scrap the filter. The solvents dissolve the
filter into the waste, which must then be treated as
a hazardous waste. Some facilities have argued
that this is counterproductive due to disposal costs
o'f liquids versus solids. Others argue that this
qualifies as treatment of a hazardous waste and
therefore is a violation of RCRA regulations1
(EPAq.p.  151).

Water-Wash  Booths

Water-wash booths capture overspray paint by
using positive air pressure to force the particles  .
into a cascading curtain of water. As a result of
being captured in the water curtain, uncured
particles of paint accumulate in a wash-water pit,
located either beneath a grating that the painters
stand on or above ground behind the booth itself.

When overspray enters the Water, it remains
sticky and can plug up holes, nozzles, pipes and
. pumps. In addition, it can form a deposit on the
water curtain, slowly building up a layer that
eventually impedes the smooth water flow down
the water curtain's face. With time, the water
 becomes contaminated with bacteria and requires
 disposal. To prevent this from occurring, the
 water needs to be treated with chemicals designed
 to de-tack overspray particles (EPAq, p. 152).

 If overall .painting volume can justify the invest-
 ment, a water-wash booth has substantial advan-
 tages. This type of booth eliminates disposal of
 filter media and allows waste to be reduced in
weight and volume. This is achieved by separat-
ing the paint from the water through settling,
drying, or using a centrifuge or cyclone. How-
ever, the primary disadvantage of this technology
is the resulting generation of large quantities of
wastewater and paint sludge. Typically, spent
wastewater and sludge requires offsite treatment,
and the paint sludge is disposed of as a hazardous
waste. Depending on the amount of coating used,
this option could use more energy, require more
maintenance time, add to chemical use for water
treatment, and/or result in additional cost to
dispose of "wet," low BTU value, heavy paint
sludges than a dry filter booth. These units are
also more expensive to install and to operate than
dry filter booths.                 '       •     .

The water-wash booth design faces substantial
challenges and more restrictive landfill regulations
than they have in the past.  Prior to 1993, some
liquid nonhazardous special wastes could be
disposed of in a landfill with little or no treatment..
EPA's decision to redefine liquid wastes and ban
certain materials from landfill disposal pertains to
 sludge generated from water-wash booths.2 This
 material still can be disposed of, however, the
 material must be.processed prior to disposal,
 resulting in a significant increase in waste treat-
 ment costs (Mitchell, p. 10).

 Baffle  Booths

 A baffle spray booth is an uncommon alternative
 to both dry filter and water-wash booths. In a
 baffle spray booth, the face of the booth has steel
   Table 43. Advantages and Disadvantages of Dry Filter Booths (NFESC, p. 3)
   Advantages
Disadvantages
   *• Decreases operating costs when compared
     to water curtain spray booths due to reduced
     chemical, electrical, sewer and water costs
   *• Reduces waste generation of wastewater
     and sludge .             "
   + Eliminates need for daily skimming and •
     removal of sludge from the booth
     Increases efficiency of particulate removal
  Is not compatible with powder paint application:
«• Has filter selection that depends on paint type
  and application
  Requires frequent downtimes if improper filter is
  used
  'For more information, see the May 1995 issue of Metal Finishing.
  2EPA's  definition of "liquid wastes" is: any material that will exude droplets of liquid through a standard
  conical paint filter within a prescribed period of time.

                                             V06

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                        Chapter 7: Application Techniques
. baffles that run the height of the booth and are
 several inches wide. The baffles usually overlap   •
 each other, forcing the air .that passes through the
 booth to change direction in order to reach .the^  •
 back of the booth. When the air does reach the
 entrainment section in the back, the paint particu-
 lates that the air is carrying fall into the trough for
 reuse. These booths are used less frequently
 because unless the facility is reclaiming paint, this •
 type of booth offers no advantages,

 Powder Coating  Booths

 In most powder coating operations, the coating is
 reclaimed and reused in the process, optimizing
 material use. Powder coating booths have smooth
 sides with steep, hopper-like sloping bottoms that
 empty into collectors and an exhaust system that
 removes powder'suspended in the air. The
 powder is drawn into a cylindrical chamber that
 has a centrifugal blower to force the powder to the
 outside walls where the powder collects and then
 falls through an opening in the cone-shaped
 bottom. The air flows,through a filter at the top  to
 remove any. fine suspended powder particles. The
 reclaimed powder can then be blended with fresh
 material.

  Best  Management Practices to
  Minimize  Coating  Defects  from
  Paint Booths
', There are a number of'steps that a company can
  take to minimize the defects that result in rejected
  work. Most of the defects require painters to
  perform rework or, in some cases, completely
  reject a part: Higher reject rates result in increased
  waste generation and reduced profits. The most
  common coating defects that relate topaint booths
  include:
  * Poor wrap when using electrostatic paints.'
     Poor wrap can happen for a variety of rea-
     sons.  However as they relate to paint booths,
     assistance providers should ensure that the   •
     spray booth has a proper ground. Wrap may
    : also occur as a result of turbulent air flow.  .

   «• Dust and dirt in  the finish. This is probably
     the most comrrion  cause for reworks and  '
     rejects. Facilities can take several steps to
     avoid this including:  avoid  having sanding or
     other dirty operations take place immediately
  outside the booth; make sure that air filters '
 ' at air intakes of the booth are not dirty,_or     ,
  have too large of a mesh size; make sure
  .thatjfhe booth is operating under negative
,  pressure;  make sure that the air make-up
  system draws  fresh air into'the booth and  - •
  that the intake stack is not too close to the
  exhaust ducts from sanding -or other dirty
  operations; keep booth walls, floor and
  ceiling free of .loose, dry, oyerspray or the
  booth blowers may pry particles  loose,
  allowing them to fall onto freshly"painted .
  surfaces;  and make sure that proper booth
  size is selected.

 * Water spots in the finish. When using a water-
  wash booth, operators must properly clean the
   nozzles above the water curtain. Omitting this
   step creates the opportunity for water droplets  •
   to settle on the painted finish.    \            .

 * Haziness (blushing) that reduces gloss. This
   problem occurs when humidity is high and .
   moisture condenses on freshly painted sur-
   faces. This is more likely to occur in a water-
   wash booth than a dry-filter booth. To avoid,
   this, parts should be moved out of the booth
   shortly after painting is completed.

  * Dry overspray on the finish. The most common
   reason for this dry overspray is that the  solvent
   is too fast. As the solvent flashes off during
   application, the overspray loses its wetness.
   This problem is usually not-a result of the
   booth but a result of high air velocity.  Proper
   monitoring and control of booth air flow
   should assist in reducing this problem. Dry
   overspray'on the finish also arises when.more
   than  one dry filter spray booth is being-
   operated at the same time. If the- air flow
   within the larger spray room is  not uniform,
    overspray from one booth can  settle on .the
    freshly painted surfaces in another booth.
    Maintaining proper air flow between  the two
    booths or providing each booth with  its own
    air make-up system can solve this problem.

  *Nonuniform coating finish with gloss,
     patches, orange peel and voids.  Numerous
     causes exist for this defect, however, .causes
     solely associated with spray booths are often
     related to poor lighting. Investment in ad-
T07

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Chapter 7: Application Techniques


  equate lighting and regular cleaning of the
  cover plates can have quick payback in the
  form of better looking finishes and fewer
  touchups (EPAq,  p. 154).
                                            108

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    Curing  Methods
     Once a coating is applied to the workpiece it
     then undergoes a curing or drying process.
While the terms drying or baking are commonly
used in the painting industry to refer to curing,
there is a distinction between drying (baking) and
curing. In curing, the resin must be converted into
a new resin, while drying refers to the loss of the
solvent so that the resin remains the same. Curing
and drying both use the two same methods to
harden a coating: air/force dry and baking (newer
curing methods such as radiation curing are
discussed as they apply to specific coatings in the
preceding,chapters). Table 44 compares air/force
dry and bake methods.

* Air Drying. In air drying, a coating film is
 Jbrmed by the evaporation of solvent, which
  leaves behind a solid film. The rate of drying is
  governed by how quickly the solvent evapo-
  rates. Moderate heat (below 194T) can be
  applied to accelerate evaporation (called force
  drying), however,, the process still basically
  remains one of air drying.
                           ^Elevated Temperature Curing/Baking. El-
                             evated temperature curing uses one of three
                             rneans: conduction, convection or radiation to
                             apply heat to the coated part (SME, p. 28-7).

                           Selecting air/force dry or bake coating (baked at
                           elevated temperatures above 250°F) is an impor-
                           tant consideration in choosing a P2 alternative.  .
                           Baked coatings usually have better physical and
                           ' chemical-resistant properties, but they also have
                           some limitations. Air/force dried coatings (defined
                           by EPA as those that cure below 194°F) have
                           special VOC limits that are usually higher than
                           baked coatings (EPAq, p. 92). Table 45 lists the'
                           typical RACT VOC limits for metal part coating.
  Table 44. Air/Force Dry vs. Bake (EPAq, p.91)
                 Air/Force Dry
                               Bake
  Curing
  Time
* Takes longer to achieve thorough
 hardness, which can affect
 production schedules      • -
* After baking and cool-down, the coated .parts
 are usually ready for assembly or shipping
  Clean-Up
  Requirements
* Overspray dries on spray booth
  filters, floors and walls; therefore,
  maintenance is not a significant
  problem.
* Uncured overspray remains sticky, making it
  awkward to walk on spray booth floors
+ Maintenance is more costly because of
  difficulty handling-the sticky material
                                                                     (continued on next page)
                                           109

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ChapcerS: Curing Methods
Table 44.  Air/Force Dry vs. Bake (EPAq, p.91) (continued)
               Air/Force Dry
                                Bake
Substrate
Versatility
 Can be applied to all substrates
 (e.g., metal, plastics, wood,
 rubber and masonry)
 Can be applied over porous
 materials such as sand castings,
 wood and paper
                                Can only be applied on metals and
                                substrates that can withstand high baking
                                temperatures. Generally not suitable for
                                heat-sensitive products such as plastics,
                                wood and rubber.
                                Should not be applied over machined or
                                other surfaces that are sensitive to warpage,
                                unless taking adequate precautions  .
                                Can cause outgassing on sand castings and
                                other porous substrates. Preheating
                                workpiece can often overcome problem but
                                adds an additional step to the process
RACT
Regulations
*Some regulations have higher
  VOC limits for air/force-dry than
  for bake coatings
 Heating
 Requirements
      dry and cure at temperatures
  from ambient up to 194°F by
  EPA definition
* Solvent-borne coatings do not
  require an oven, although a low
  temperature oven will speed up the
  drying process
* Water-borne coatings would
  benefit from a low temperature
  oven that will speed up the drying
  process .
  • Offers  lower energy use
                                 Generally must cure at a minimum of 250°F.
                                 A typical curing schedule is 10 minutes at
                                 350°F. Curing times are inversely
                                 proportional to temperature. A cool-down
                                 staging area is required.
                                • Requires high temperature oven, and
                                 therefore greater energy use
 Physical/
 Chemical
 Requirements
• Most single-component coatings,
 such as alkyds and modified
 alkyds, do not exhibit superior
 physical and chemical properties
<• Single-component moisture-cured
 polyurethanes, however, do
 perform comparably to Iwo-
 component polyurethanes and
 baked coatings.
                                 * Often have excellent physical and chemical-
                                   resistant properties, sometimes similar to
                                   two-component polyurethanes
 Appearance
 Defects
 * Surface defects, such as orange
   peel, often do no? flow out during
   the drying and curing process. .
   Force drying at elevated
   temperatures below 194°Fcan
   partially alleviate this.
                                + Films tend to flow out better when in the oven
                                  providing smooth finishes and eliminating
                                  surface defects such as orange peel.
                                            110

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                                                        Chapter 8: Curing Methods
Table 45. Typical RACT Limits for Miscellaneous Metal Parts Coating
         (EPAq,p.93)
'
California
Most other states .
Air/Force Dry
Ib/gal g/L
2.8 '• • 340
•' 3.5 420 ' '
Bake
Ik/gal g/L
2.3 ' '275'
.•.••;• 3.0 . 36.0
                                   Ill

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112

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    Equipment   Cleaning
     When a painting process is completed, a color
     change is needed, or maintenance is
required, the metal cbater must clean the equip-
ment. There are numerous P2 opportunities for
reducing waste and air emissions in equipment
cleaning operations.

General  Description

All coating practices require some type of equip-
ment cleaning. For spray painting, the most
common coating1 operation, spray guns and
accessories must be cleaned between color
changes, when orifices clog and often at shift
changes (IWRC,P: 15).

 Pollution  Problem

External equipment surfaces generally are cleaned
by soaking, wiping or flushing with solvent. If
equipment cleaning is done in an open container, a
 significant quantity of solvent is lost to evapora-
tion. Internal parts and passageways as well as
 paint guns are commonly cleaned by flushing
 solvent through the gun and orifice. This practice
 also results in significant evaporation and loss of
. usable product (IWRC, p. 15).

 P2 Options

 A cost-effective method for reducing wastes is to
 eliminate unnecessary cleaning. For equipment
 that requires cleaning, making improvements in
 operating practices that minimize solvent use and
 reduce evaporation should be implemented
 wherever practical. Using a gun washer to clean
 spray guns is one example. Various solvent
 recovery and reuse technologies are also available.
 In addition, alternative cleaning solutions can be
 used. Each of these options is discussed below.

 Scheduling Improvements

 Implementing better operating practices and
 scheduling can significantly reduce waste gener-
 P2 Tips for Equipment Cleaning

,* Eliminate unnecessary cleaning
 * Improve current operating practices
 * Use a gun washer
 «• Recover and reuse spent solvents
 * Use alternative nontoxic cleaning solutions
ated from cleaning operations. The amount of
waste generated is directly related to the number
of times paint color or paint types are made. For
this reason, scheduling improvements have
perhaps the largest effect on the volume of waste
produced from cleaning equipment. Making large
batches of similarly produced items instead of
small batches of custom items, increases the time
between cleaning. Additionally, scheduling paint
jobs so that they move from the lightest color to
the darkest can also reduce the need to clean.

Eliminate Unnecessary Cleaning

When assessing the cleaning process, all the
typical cleaning tasks should be reviewed to learn
whether cleaning is necessary. While most coaters
assume that spray guns, tips and lines must be
cleaned for reuse, cleaning some low-cost items
mightnot be advisable; Costs from cleaning
solvent purchases, solvent waste disposal and
solvent emissions could be higher than simply
replacing the item being cleaned. However, the .
.costs of proper disposal must be factored into any
decision (MnTAP, p. 5).

 Improve Current  Operating
 Practices

 A technical assistance provider should also help a
 client company review the ways in whichcleaning
 solvents are handled. All solvents should be stored
•. in covered containers when npt in use. Leaving
 solvents in the open air creates unnecessary
. solvent waste and VOC emissions. In addition, the
 company should set a standard for the minimum
                                         113

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Chapter 9: Equipment Cleaning
  CASE STUDY:
  Crenlo, Inc. - Spray Nozzle Selection Reduces Solvent Waste Volume

  Crenlo, Inc. manufactures products from steel and aluminum. Finished products are coated with
  saked enamel paint. Most colors are prepared onsite. Paint from any batch may be stored for
  uture reuse. To ensure proper quality, the paint is remixed and strained to remove solids larger
  han the 90 mesh screen size, before delivery to spray booths.

  n the past, the straining equipment was cleaned using fresh solvent sprayed from a hose fitted
  with a nozzle spraying a flat fan of solvent from a 0.1 72 inch diameter orifice. This nozzle is rated
  or 4.3 gallons per minute (gpm) flow with a 30 pounds per square inch (psi) supply pressure.
  Annual cleaning of the straining equipment produced about 14,000 gallons of waste costing at
  east $ 16,000 per year. The cleanup solvent is a recycled blend that is distilled offsite and  re-
  umed to Crenlo. A single charge covers both purchase and processing costs. The.4.3 gpm
  nozzle was originally selected because this size nozzle was already in use on an aqueous spray
  wash line at the plant, so a supply was available onsite. A technical assistance assessment identi-
  fied that nozzle size was the key factor affecting the volume of solvent used.

  Three nozzles were purchased and tested in the cleaning system. Flow rates for these nozzles
  ranged 'from one-fourth to one-fiftieth of the original flow rate. The smallest of these nozzles'
  orifices (0.026 inches) cleaned the equipment at an acceptable level in 60 to 90 seconds at 30
  psi, and used 80% less solvent than the original nozzle. Waste accumulation,from this source was
  mo'nitored over the next two months and confirmed the improved efficiency using the new nozzle.

  Foreign particles (such as rust) in the solvent feed line plugged the nozzle orifice frequently over
  the first 2 weeks of operation. Plugging was eliminated by installing a small in-line basket filter to
  remove solids before they reached the nozzle. Cleaning time with the low-flow nozzle was
  doubled or tripled compared with the original nozzle. The 60 to 90 second cleaning time was
  judged acceptable, although operators were not pleased with this change. Cleaning time was
  reduced by 30 seconds by instituting a presoak step. The presoak used a dirty solvent bath to
  remove or loosen most of the paint. The equipment was then sprayed with fresh solvent for a  final
  rinse. The presoak resulted in additional waste reduction.

  ^Savings
  There was no capital investment for this project. Supplies included the purchase of three nozzles
  for testing ($70) and a small, in-line basket filter ($50). Six hours of labor were needed to test the
   nozzles, and approximately 4 hours were spent unclogging the nozzle orifice for the first 2 weeks
  of operation. Total implementation costs were approximately $270. Reduction in waste resulting
   from the new nozzles came to about 11,000 gallons less of spent solvent waste generated per
   year with'savings of approximately $13,500 per year.   ,
                                                                          (MnTap 6/91-83]
 strength necessary for cleaning in order to ensure    The paint gun is partially disassembled and placed
 that used solvent is disposed of or recycled only    in the unit. Cleaning is accomplished by recirculat-
 when it loses its cleaning effectiveness, not just     ing solvent sprays. These units reportedly reduce
 because it looks dirty (MnTAP, p. 5).             solvent waste by 50 to 75%. VOC emissions can
                                               be reduced by up to 20%, and a 60% labor time
  Use  a Gun Washer                     savings can be achieved (IWRC, p. 15).

 The use of a gun washer can also help to reduce             §   c    Q     Q() ^     ^ tQ
  wastes generated during equipment cleaning. An    ^VJJ^ $1 5QO for industrial ^ units
  automatic gun washer operates like a dishwasher.   approximately *  , jvy             jv

                                            114

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(i.e.. gun and paint hose wash). Similar units may
also be leased through various chemical suppliers
and waste management companies at a cost of
$ 165 to $ 195, per 5 gallon waste solvent change.
out interval (lWRC,'p.  15-17).      .    ;

Pressure  Pot Liners  .'"'.'

For maintenance of pressure pots, many compa-
nies use a polyethylene inner liner with the
pressure pot. The main advantage of this practice
is that only a small amount of paint comes into
contact with the steel or stainless steel body, and
cleaning the liner requires only a small amount of
solvent. After pouring-solvent into the liner, the
operator should swirl it around for a few seconds.
The operator can then discard the spent solvent
into a hazardous waste drum and the liner is ready
to be reused.         -

Some operators choose to allow the paint that
sticks to the side of the liner to dry out, which
causes it to flake off with ease. If the solid paint is
shown to be hazardous per RCRA guidelines the
facility must manage it as a hazardous waste. If it
  CASE STUDY:
  Solvent Reclaimer

  The Mormon Motor Company of Garland,
  Texas, spent $ 10,000 to. install a solvent still
  that reclaims thinners from paint-related
  wastes. By installing this standard technol-
  ogy, MaVmon reduced its disposal of
  thinners from 34 drums to 3 drums and cut,
  procurement of new'thinner from 4,000
  gallons to 2,000 gallons per year.
                    4  . ' •'      .         '
  * Savings.             '.'-•••
  As a result, waste disposal costs were
  reduced from $6,200 to $1,400 per year.
  Purchasing costs for new thinner decreased
  from $9,500 to $4,750 per year. Even with'
  additional labor costs at about $5,000 a
  year, the annual savings were approxi-  '
  mately $4,500 with a 2.2 year payback
  period (PPIFTil 994).       .'-...
                                                                      Chapter 9: Equipment Cleaning;
is not hazardous, it can be discarded with the rest of
the solid waste. The liner should then be reused
(EPAq,p. 137).       "  •

Use Alternative Cleaning
Solutions

Because of the increased need to reduce VOC
emissions, alternative cleaning solutions are avail-
able. They include dibasic esters (DBE), N-methyl-
2-pyrolidone (NMP), and a variety of other
alkaline-, citric-, and water-based solvents suchas
d-liminone, naptha, and terpenes. These chemicals
have reduced VOC emissions due to their lower
evaporation rate. Although toxicology information
specific to these chemicals is relatively limited at
this.time, many researchers believe that the relative
safety of similar chemicals indicate that they are a
feasible alternative to organic solvents in certain -
applications (MnTAP, p. 5-6).'

Recover  and Reuse  Spent Solvents

Orisite recycling of used solvent is another way to
reduce waste and save ihoney. Savings come from
reducing the amount of solvent purchased and the
volume of spent solvent that must be sent offsite for
costly disposal. Two common methods of solvent
recycling are settling and distilling (MnTAP, p. 5-6).

Settling involves putting used solvent in a container
and letting the particulate matter settle out. The
container should be designed to allow for removal
of solvent without shaking up the sludge mat has
settled out (MnTAP, p. 5-6).  Solvents can be used
for gun cleaning and then can be placed back into
the storage container for subsequent settling and
reuse. Eventually,  sludge will make up the majority
of the container and offsite hazardous waste
'disposal will be necessary. At this point, the pro-
cesses can be repeated using a different container.
Solvent waste reduction of up to 33% can be
accomplished with this.simple method (IWRC, p.
 15-17). Filtering equipment, which removes the
particulate matter from solvents, also is available
(MnTAP, p. 5-6).

Waste solvent also can be collected and processed
through distillation equipment. Approximately 80%
 1 For more information on these alternative solvents, see Project Summary:  SAGE 2.1, Solvent Alternatives
 Guide: User's Guide. Research Triangle Park, NC: Air and Energy Engineering Research Laboratory. EPA/
 600/SR-95/049:  .      ..'..'.  .  '.                     '               .                 •    •
                                            115

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Chapter 9: Equipment Cleaning
  CASE STUDY:
  Paint Gun Cleaning

  Thermon is a electronics manufacturer in
  San Marcos, Texas, with 300 employees. To
  clean paint guns, the company traditionally
  soaked the guns in solvent. This method
  generated significant amounts of solvent.
  waste and even clogged the guns when
  inexperienced personnel performed the
  cleaning.

  To remedy this situation, Thermon purchased-
  a spray gun cleaning system that circulates
  solvent through the gun. The cleaning solvent
  is filtered to remove particles that clog the .
  paint gun, enabling the solvent to be reused
  several times before disposal. The system
  decreases solvent purchases and effectively
  cleans the paint spray gun even when
  inexperienced personnel perform the clean-
  ing.                      -

  To prepare the paint guns for the cleaning
   system, the remaining paint is emptied from
   the canister and the canister is washed with a
   small amount of solvent (Vz pint). The
   remaining solvent is poured out before the
   gun is loaded in the cleaning system. This
   extra rinsing step significantly reduces solvent
   use.

   * Savings
   With the new cleaning system and methods,
   Thermon reduced solvent use by 60%.

   The  cost of the spray gun system was $700.
   The  system was found to be very economical
    due to reduced solvent costs and, more
    importantly, improved spray gun perfor-
    mance due to increased cleaning effective-
    ness. Despite the fact that Thermon does a
    relatively small amount of painting, the cost
    of the unit was recovered in 6 to 8 months
    (PPIFTI1994).
of the used solvent is recovered with basically the
same cleaning properties as a new product. The
remaining 20% sludge (still bottoms) must be
collected for offsite hazardous waste disposal. To
help maintain the cleaning properties of the
recycled thinner, certain paint and solvent wastes
should be segregated. Waste gun wash solvent and
any waste lacquer paint and thinner mixtures can
be included for recycling. All waste urethanes,
enamels and enamel reducers should be placed in
a separate container; enamel and urethane prod-
ucts will not clean as well as pure lacquer thinner.
By segregating the two, the reclaimed solvent will
possess cleaning properties like a virgin thinner.
This waste management technique has the advan-
tage of reducing the volume of virgin thinner
purchased as well as. the amount of waste thinner
generated (IWRC, p. 15-17).

Onsite distillation equipment comes in a wide .
range of capacities, from 5 gallons per 8 hour shift
batch operations to more than 100 gallons per
hour flow-through units. Costs for 5 gallon batch
units start at approximately^ 1,500 with an
average cost of $3,000 (IWRC, p. 15-17).
                                             116

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 Index
Symbols
100% solids coatings 66
1, ], 1 -trichloroethane 58;
2-ethoxyethanol 13
2-nitropropane 13
139
A          '         ..'         '  '   -•   •"
abrasives 29
acetone 7,  13, 36, 141,148   ~.   •;
acidic chromate 39  .
acrylic melamine paint 4
acrylic paint'; 4                        .
acrylic resin 4, 74-
acrylic-urethane'coatings 71            '  .
acrylics 59, 60,  67,  71,  77,95,  137
additives 2,  41, 52, 57, 59, 62,  65,   -*  '
  76, 95,  101, 137, 138,  140
adhesion 2, 30/33, 37, 38,-39,  41,
  59; 60, 70," 71,. 72,  74,  77, 78,  79,
  80, 86, 97, 98, 135,  136,  142,  144,  146
air drying 109
air emissions 4, 25, 50, 61, 65,  76, 78,80,
  88,' 113,127
air releases 7, 8           /
air-assisted airless systems 92
air/force dry coatings 64
airless 66, 85,  87, 91,  92,  93, 94,-123,
   102, 131,137
airless spray 80, 83, 87, 89, 91,92,93,131,
   137
alcohols 7, 35, 36, ^57,  67, 80,  137,141,
   144
aliphatic hydrocarbons 36, 57
glkyd resins 62
alkyds 4, 60, 110, 137          '   .
alternative coating^ 57, 61,123
alternative solvents 31,  33, 115
alumina 41, 52
aluminum alloys 46                 ',-•''
aminoplasts 59       •
anodizing 3, 31, 36, 37,38,  117,124
antiskinning agents 59
application standards 83, 84,  86
application techniques 1, -19, 83
applied film thickness 85
-.aqueous cleaning  18, 32, 119,120,137,  139
architectural coatings 2
aromatic hydrocarbons 57
 autodeposition 96,  97,  138
 automated aqueous washer 34

 B
 baffle/spray booth -104,  107
 bake coatings 65,110
 barriers 16, 17, 81,  118.
 ba'secoats 3
 baseline 16, 18, 19, 21, 23, 64, 66
. benzene 7, 13,  138
 binders 2; 57, 59, 60, 62, 67,  138, 141
 'biocides 59, 138
 black alkyd 4    '
 blast stripping 42
 blasting cabinet 42
 bonding adhesive flash 46
 brushes 6, 139      -            .
 burnoff ovens 53,54
                    cadmium 13, 46,  51,  59
                    can coating 10, 74
                    carbon dioxide blasting 50
                    carbon dioxide pellets 42, 46
                    carbon oxides 52
                    carbon tetrachloride  13
                    case studies 1 7, 22; 1.18,119,124
                    catalysts 59, 65, 83                    •
                    cation exchangers  37
                    cellulosics 59                  '
                    CESQGs 11        '       .  • .   •   .
                    CFC-11335, 36, 58,  148
                    chemical and electrochemical conversion 36
                    chemical stripping 21, 29, 41, 43, 45, 46,
                       47, 50   ' .       .
                    chemical use 40, 6\
                    chromating 3                      . '  .
                    chromic acid 37, 38, 39
                    chromium 13,  32, 38, 39, 59
                    Clean Air Act  7,  8, 9, 30
                    'Clean Air Act Amendments  7, 8, 9
                    Clean Water Act 7,  12
                    cleaning 113
                    cleaning capacity 31
                    cleaning methods  25, 26
                    cleanup and disposal '35, 48
                    clearcoat finishes 74
                     CO2 pellet blasting 47, 48, 49
                                         117

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CO, snow blasting 48, 49
coating process 3, 4, 5,  7, 15,  18, 22
Coatings Alternative Guide 57,  117, 123
coatings application  14, 83
cold cleaning 30,  32, 33, 35
cold-solvent degreasing 32
colloidal coatings 67
colloids 59
colored pigments 59 .
completely enclosed vapor cleaners 32        '
compliance 6,  7,  9, 11, 15, 16, 61, 69,
   76,117,118, 124
compressed air 21, 28, 45, 47, 48, 49,50,
   83,  88,  90,  91,  117,123,137, 145
Conditionally Exempt Small Quantity
   Generators 11,12
conduction 109
contamination sources 30
control equipment 4
control technique guidelines 8
convection 109
conventionaLair atomizing 85  •          ,
conventional air spray 57, 86,  87, 88, 101,
    131
conversion airsystems 90
conversion coatings 3, 29, 30,  36, 37
corrosion resistance  1, 3, 30,  37, 38, 39,
   59, 60, 61, 68, 69,  70, 71, 75,  77, 78,
   96, 142,  143, 144
 cosolvents  41,  68,  140
 countercurrent cleaning 31.
 cresols 13
 cresylicacid  13
 cryogenic stripping  53
 curing 2,  3, 4, 31
 curing methods 109
 curtain coating 3, 77, 98
 cutting fluids 18,  35
 CWA7, 11,  12, 14
 cyclohexanone 13
 cyclone centrifuge 42, 44

  D
  d-limonene 33,35
  defoamers 59 '
  dense particle separators 42,  44
  dip coating 3, 76^.89,  97, 98/138,
    140, 141
  dip tank 30
  dirt 29, 30,  70,  79,94, 107
  distillation/recycling practices  27
dry booths 101, 105
dual adjustable air wash 42,  44
E-coat95, 96, 138, 141, 143, 147, 148
economic feasibility  16,  18
edge buildup  85
electrocoat 4, 96
electrocoat primer 4
electrodeposition 27, 68, 83, 89, 95, 101,
   138, 139, 141
electrodialysis 38
electrostatic 21, 27, 48, 63,  64,  66, 68,
   69,  72, 73,74,  76,  78, 80, 81,  83, 84,
   85,  86, 87, 89, 93, 94, 95, 96, 101,
.   103,107,123,131,  141,  143,148/149
electrostatic fluidized bed 72
electrostatic spray 68, 69, 72, 76, 83,  86,
   89,  93, 94, 96,101, 141, 143
emerging technologies 61,79
emissions  1, 4, 6,  8, 19, 21, 22, 25,  26,
   27-,  29, 32, 33,  38, 44, 47, 50, 53, 61,
   62,  65, 66, 67,  68; 69, 70, 75, 76, 78,
   80,  81, 84, 85t  88, 90, 91, 94, 95, 96,
   97,  99, 101,  102, 105, 113, 114, 115,
   127, 130, 131,  133
 employee participation 17
 emulsions 148
 epoxies59,  60/65, 67,  71, 76, 77, 78,
   95,105,  137,141       •    ,
 epoxy polyester hybrid coatings 71
 epoxy resins  141
 equipment cleaning  1, 2, 4,  9, 14,  19, 26,
   27, 28, 58, 84, 113, 114  •
 esters  7, 36, 41, 57, 67, .115, 137, 144
. ether  7,13,  36, 139,  144    -  •
 ethyl acetate 7, 13
 ethyl ether 13
 evaporation systems 37       •-'..-
  Faraday cage effect 75, 95, 141 .  .
.  federal regulatory status 7
  Federal Water Pollution Control Act 12
  fiberglass 44, 46, 61, 101/  1.05
  field stripping 42, 43
' film thickness 65, 66, 84, 85, 86, 95, 98,
    129, 130, 151
-  filters 25
  filtration 37, 45, 48,  147
  •flamespray 51, 73    .
                                           118

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flash lamps 53        ••          ,.
flash rust 40
flattening agents. 59
flow coating 3, 27, 66, 83, .89,',95, 98,
   141, 142'  '
flow modifiers 59
fluidized bed paint removal 51
.fluidized bed stripping  51, 53
fluorocarbons 13, 59, 74
freeze/thaw stabilizers 59
functional pigments 59
fungicides 59, 1 37
 garnet 41 , 42, 49   •.
 glass beads 41, 42    -,     ...
 glove box 42                '     .  :   ,
 glycol ethers  7
 good housekeeping practices 25
 graphite 46
 gravity separation 28
 gun setup 87
 gun washer 27, 1 1 3, 1 1 4          -    •

 H
 halogenated  solvents 3, 13,  29, 31, 58,  142
 hanger 42
 HAPs 95,  100, 127
 hazardous air pollutants 8, 36, 59,  1 1 8
 hazardous wastes 7, 9, 10,  11,  13,20, 61
 health effects ofsolvents 57, 58
 heavy metals 2, 9,  10, 14,  30, 36, 59, 66
 high solids 1, 21, 62, 64, 66, 67,117,  133
 high transfer efficiency equipment 25, 26
 high-solids coatings 26, 61,62,64,65, 66
 high-temperature thermal methods" 53
 HVLP 21, 80, 85, 87, 88, 89, 90, 91,
    101,102, 117, 123,  130,  131,133
 hydrochlorofluorocarbohs 36  •
 hydrofluoroethers 36
                         .
  ice crystals 42
  immersion strippers 41    .
  inventory control 21-, 25, 26, 27, 88
  ion exchange 38
  iron phosphating 39
  isobutanol 13
K     ,
ketones 7,36, 57, 144
lamp 78,  79
large quantity generators 1,1
laser ablation 34, 55
lasers 53
latex paints 67
lead 8,  13,  2'5,  29, 32, 43, 44, 46, 49, 50,
   51, 53, 59,. 80, 81, .84, 86, 87,  105,
   136, 149
low pressure, low volume paint spraying 91
'low-volume high-pressure 57
lower-temperature cures 74
LQGs 11         '•-.'.-
LVHP 57,  61, 80, 84,  88, 89, 90, 93, 94

M
M-pyrol 36                             .
machining 1 8, 22, 30, 35
machining operations 22
MACT standards 8, 9/32
 magnetic separator 42, 44
 manganese phosphate coatings 39
 material handling 26,  27    __ .  •
 maximum achievable control technology 8  •  .
 measure cleanliness 31
 mechanical cleaning 29, 33
 medium-pressure mercury-electrode arc 79
 MEK 57,  76  .  .  -   ,  .   '
 melamine 4, 42., 62, 65
 melamine-formaldehyde 65              /  . ...
 metal filter 28
 metal scale 29                   .
 methanol 13
 methyl ethyl ketone 7,  1 3,  32,  57,  58,  76   ^
 methyl isobutyl ketone 57
 methylchlqrofluorocarbons 35
 methylene chloride 13, 36, 41, 47, 58, 139,
     148
 MIBK2,  6,  8,  32, 57                   ;
 molten salt baths 53,  54,  56
  molybdicacid 39         -   -  .
  monomers  76,  7.8
  multiple vibrating classifier screen decks  42,  44
                                              n-butyl alcohol 13
                                              n-methyl-2-pyrolidone 36, 115
                                            119

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national ambient air quality standards 8
National Pollutant Discharge Elimination System
   12
natural oils 59
nitrobenzene 13
nitrogen oxides 59
NMP 36, 41, 115
nozzles 21, 47, 51, 89, 106, 107, 114, ,133,
   141        .
nylon  60, 71               .

o
obstacles 17, 19
oils and greases. 3,  30
oligomers 76, 78
on-site distillation 28, 116
open-top vapor cleaners 32
operating parameters 15,19
operating practices 1,19, 25,  27, 29,  30,
   83, 84,  88,  113
operator error 84                  .       .
operator training 26, 27, 44,  47, 50,  52,
   92, 93/102
organic solvents 9,14, 36, 67, 69, 97,115,
   139, 140
ortho-dichlorobenzene 13
OSHA30,  32, 43,  86,  123
overspray 4, 10, 26, 54, 66,  75, 80,  83,
   86, 87, 88, 89,  90, 91, 101,  102,  105,
   106,107,108, 109, 129,  144,147
ozone 8, 32, 36, 59, 79, 141, 145, 148
 P2 options  1, 6, 22, 27, 30, 83, 84,  113,
  .129
 paintbooth 91, 94, 101, 129
 paint characteristics 84
 paint heaters 65
 paint mixing 25
 paint overspray 54
 paint sludge 4, 32, 53,  69,  83, 106
 paint stripping 29, 31, 42, 43, 44, 47, 51,
    139
 paint thinners 10
 perfluoroccrbons  36
 performance monitors 20
 personal protection equipment 49
 phenol formaldehyde 42
 phenolic acids 41
 phenoiics 59
 phosphate coatings 3,-39, 140
 phosphating 3,  36,  38, 39, 40,  1 42, 1 44
 phosphoric acid 39, 144
 photoinitiators 75, 76
 photopolymerization 75
 pigments  2, 8, 27, 43, 45, 59, 64, 79, 81,
   92,  141
 pilot testing 18
 plastic media blasting 42, 43, 45, 56
 plasticizers 59,  137
 plural component proportioning systems 99
 PMB  42,  43, 44, 45, 46, 47
 pollution prevention  1 , 2, 3, 6,  7, 8/15,1 6,
   17, 18, 19,  22,  23,  25, 31,40,61,88,
   95, 1 1 7, 1 1 8, 11 9, 1 20, 1 21 , 1 24, 1 26,
    133
 pollution prevention options  15,  18,  19, 22
 polyester 42, 62, 65,  71,  72, 74, 144; 146 .
 polyol-isocyanate coatings 79
 polypropylene 71
* polystyrene 101, 106, 148
 polyurethanes 59, 60, 62, 65', 105, 110, 143
 polyvinyl acetate 67, 1 47
 polyvinyl chloride 62, 71, 147
 POTW 11
 powder coating resin properties 72, 77
 pressure assist cup system  90
 pressure pot liners 115
 pressurewashing 35
 pressure water blast systems 51
 pressure water stripping 5 1
 pretreatment 4,  11, 14, 29, 34, 40,74,131,
    141, 144
 pretreatment coatings 40
 prime coat 3, 4
 process flow diagrams 1 8
 product coatings 2, 65
 production rate 84,  97,  104   . '
 publicly-owned treatment works 14        •
 pumps 21, 25, 68, 92,  106
 pyridine  13     ,                   .
 quality of finish 84
 quality standards  8, 18, 45
  RACTLimits 8, 111
  radiation 61,  64, 75,  76,  79,  81,83,
    109, 118, 119,140
  radiation curing  75,  76,  109,119
  RCRA7, 9, 11,  12, 43, 44, 115
                                          120

-------
•records: 11, 12,  18,  19/21,  127
 recover and reuse spent solvents 1 13, 115
 recycle cleaning solvent 31            •  '   -
 recycling solvents'25, 28
 regulations 6, 7, 8,  9, 1 5, 18, 30, 36, 66, "
   68, 69,  76,  89,  106,  110, 117,124,  133
 reverse osmosis 37, 145
 rework 30, 87,  107        '   '   ;
 rinsing 14,. 27,  38, '40,  54, 96, 116
 roll coating 83, 98, 99, 104, 145
 roller 3,  27,  66,  83,  89,  95, 99
 rotary atomization 94
 rust 3,  29, 39,  40,,43, 49,  50, 67, 114,
  .-•145  "•-•''
 sand 29,  42,  43,  44,  51,  110
 scheduling improvements  113
 scrubber water 4,  83
 sealants 41 r 46, 48-
 sedimentation 37.
 .Significant New Alternatives Program 36
 silica-containing materials 29
 silicone 4, 36,.60, 142,. 146  :
 siphon-fed system 89
 sludge 4, 14-, 19, 21, 27, 28, 32, 38, 39,
   40, 41, 46, 53, 69, 75, 83, 106, 115,
    116
 soda stripping systems  45
 sodium bicarbonate 41, 42, 45, 46, 51, 56
 sodium'brcarbonate slurry 42'
 sodium hydroxide 41,  143
 solvent cleaning systems 30
 solvent distillation  28
 solvent emissions 6, 32,  65, 101,  113
 s'olvent gravity separated  21 .
 solvent vapor degreasing  27, 30,  31,  32,34
 solvent-based chemical stripping 29 .
 solvents  1, 2, 3, 4, 5, 6,  7,  9, 10, 13, 14,
    17, 21, 25/26, 27,  28, 29, 30, 31, 32,
    33, 34, 35, 36, 41,  43, 44, 47, 57;. 58,
    65, 66, 67, 69, 71,  75, 76,78, 84, 91,.^
    97, 98,  99, 106,. 113,  115,  118,127,
    133,  137, 138,  139, 140, 142, 144,145,
     146,  147,148
  source reduction 16
  spatulas. 21  .              .
  special purpose coatings 2
 .spentsolvents 4, JO,  13, 27, 36, 113,115'
  spigots 21,  25         ,
  •sponge  blasting systems  49, 50, 51
 sp'ray.application technique 84
 spray booth 4, 25, 109, 139, T49
 spray booth configuration 84          .
 spray booth filters 25 •
 spray distance 84,87
• spray guns 4/  21, 25,  83,  84, 85, 86, 88,
  -90, 91, 93,95, '100, 113, 133/'l38,  149
 SQGs 11      '.;.•-,    ; •  •        '     :
 stabilizers 37, 59                 ' ..  „
 steel grit 41     .          .   t    .  ''
 storage 3, 11, 12, 18,  20, 21/25, 26, 27,
   30, 44, 46, 57, 63, 65, 69, 70,  72,  75,
   88, 115  .          "        '   ' . '  .
 stripping operations 29, 41, 42,  43, .44,  43,
  ,46            •;       .      '  .
 styrene-butqdiene copolymers 67
 sulfuric acid anodizing '117
 supercritical carbon dioxide 79, 99, 100;.1 18 •
 supercritical fluid cleaning 35
 surface coat  138
 surface preparation 1,  2, 3, 9, 14, 1 9, 29,.  ,
   30, 31, 40, 47, 48, 55,  56, 58, 61,
   62, 84/117,123, 135,  145
 surface treatment baths 29        .
 surfactants 49          ",    '

 T        '         •        :   -   ",  "  :
 TCLP 11                ,
 team approach  18, 21   .
 technique training 20-        ,
 terpenes  33,  115,146
 testing 18, 31,  74/85, 87, 114,119,135,"
    136.          .
  tetrachloroethylene 13
  TGIC polyesters 71
  thermal capability 30       :
  thermoplastic polyester 71,72
  thermoplastic powder coatings 71, 72, 73, 147
 . thermoplastic resins 71, .144,146
  thermoset resins  71            •    .  -     •
  thermosetting epoxy-resin-based paint 4
 'thickeners 41, 59
  Title III air toxics program 8
  toluene 2, 6, 7, 8, .10, 13, 32,-57, 58, 76,
    '138.      .       '  - ..  -    :
  topcoats' 3,  4,141         .
  Toxic Release Inventory 12
 -Toxicity Characteristic Leaching Procedure 11 .'
  training  11,12, 20, 23, 25, 26, 27,  32,
    44,45,47,  50, 52, 87, 93, 96, 102,
    103,117,119,120, 123, 131
                                           121

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TRI  12
trichloroethylene-36,  58
trichlorofluoromethane 13, 148
triggering 85, 87
trimethyl benzenes 57
two-component reactive liquid coating 65
two-step paint application/curing 2
Type I'anodizing  37
Type II anodizing 37
Type III anodizing 37 .        .

u
ultrafiltration 40,144, 147
ultrasonic cleaning 34,147
unicoat Paint 79, 80, 81
urea formaldehyde 42
urethane polyesters 71
water-soluble solvents -41'
water-wash booths 104,  105,  106,  107
wet booths 101
wheatstarch 42, 45, 46, 47,56
wheat starch blasting 45, 46, 47 ,
white pigments  59
wipe cleaning 35
wraparound 93, 95

X
xenon lamps 53
xylene 2, 6,  7, 8, 10, 1.3, 57,58, 138
xylene isbmers  6     .
zinc phosphating 3, 39, 142
 vacuum de-oiling 34
 vacuum sanding system 43, 44
 vegetable oils 59, 60
 vibratory deburring 34
 vinyl coatings 46
 vinyls 59, 60, 67
 viscosity 21,  57,  62, 65, 66, 67, 78, 83,
   87, 89,  90,  91, 94,  97,  98,100,101,
   102,104,  123,140,  147, 148, 149
 VOC content of coatings  10
 VOC emissions 4, 26, 27, 32,  66, 69, 80,
   81, 84,  85,  88, 95,  96,  97,  99,  105,
   113,  114, 115, 11.7,131

 w
 waste exchanges 25, 28           ,  •
 waste management 19,  20,  1,19,120,125,
    126
 waste minimization plan  11
 waste reduction 17, 20,  40,  114, 115,119,
    120,121,126
 waste stream 1,  20, 29, 38, 45, 46, 51,  53
 wastes 1,4
 wastewater4, 12, 14,  15, 33,  38, 43, 44,
   45,  46, 50, 52, 55, 56,  69, 70,  106,
    118
 water use  19,' 40, 47            \   •   .
 water-based alkyds 67
 water-based Coatings 69
 water-dispersible paints  67
 water-soluble paints 67
                                          122

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References
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Binks. Operator Techniques. Franklin Park, IL:
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                                           123

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  EPAn. 1995. Project Summary: Evaluation of
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EPAp, 1996. Draft Metal Finishing Compliance
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EPAq. 1996. Pollution Prevention in the Paints
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EPAr. 1991. Guides to Pollution Prevention; The
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EPRI. 1994. Ultraviolet Curing Technology.
Columbus, OH: EPRI Center for Materials
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EPRIb. 1994. UV Curing of Coatings on Metals.
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Falcone, Sal. Reducing Air Toxics and VOCs in
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Farrell, Ron. Powder Coatings in Metal Finishing
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Ferrari, Robert F. 1995. Waste-water Recycling:
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 Ford, Christopher, and Sean Delaney. 1994. Metal
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 Freeman, Harry M. 1995. Industrial Pollution
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 GIL October 1991. Fabricated Metal Product
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                                            124

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Haveman, Mark. 1995, Profile of the Metal  ^
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Hunt, Gary E. 1,988. Waste Reduction in the
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Iceman, L.E. Wine and Coatings: Different, but
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January 1996.                      .

IHWRIC. 1992. Paint Waste and Disposal
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IHWRICb. 1994. Spray Painting Options.
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'iHWRICc. T994. Methods of Paint Application.
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                                             125

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MnTAP. 1994. Waste Reduction Alternatives for  '
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MnTAPd. 1996. Reduce Costs of Finishing '
Operations by Empowering Spray Operators by
Paul Pagel in MnTAP Source. Summer 1996.
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Program.

MnTAPe. Alternative Cleaning Technologies for
Vapor Degreasing and Cold Dip Processes.
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Program.         •           ' <

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                                            126

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       - V'        , =
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                                             127

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128

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   Appendix  A
   Information   Resources
Trade  journals  .

The following trade journals can provide up-to-date
information on coating developments. Many of these
journals have annual guidebooks and directories,
issues with articles on coatings technologies, and
vendor listings.

Journal of Coatings Technology              •
•Surface Coatings international
American Paint and Coatings Journal   :   •
Modern Paints and Coatings     .
Metal Finishing          ,   , '
Chemicalweek
Chemical Marketing Reporter

Manufacturers/Literature

Binks Training Division (Franklin Park, IL) offers a
variety of training materials on spray painting and
related topics, including seminars, videotapes and
literature: For more information, contact:
Binks Manufacturing Company
9201 W. Belmont Ave.
Franklin Park, IL 60103
Attn: Training Division

the following is a list of literature available from
Binks:                     '   , •-'-••      ~ .
'Material Supply. TD2-1R-6.
Hose and'Fittings. TD3-1R-2.    ;   "••'•'.'"•-
Compressed Air Supply. TD4-1 R-6.
Automatic Spray Equipment. TD5-1R-4. •
Spray Booths. TD6-1R-5.                  ,
 Compressed,Air Spray Gun Principles. TD10-1 R-4.
 High Volume Low Pressure-HVLR TD10-4R.
 Airless Spraying. TD11-1R-4.
 Air Assisted Airless Spraying. TD11-3R-2.
 Plural  Cofnponent'Spray Systems. TD16-1R-4.
 Electrostatic Spraying. TD17-1R-4.
 Electrostatics Safety Manual for Liquid and
 Powder Finishing Systems. TD1 7-2R-.
 Hot Spraying: TD42-1R-5.             .
 Operator Techniques. TD49-1R-3.
 Spray  Application Processes. TD49-2R-4.
 Paint Curing by Infrared Catalytic Thermoreactors.
 TD10Q-7.''.v
 Viscosity. TD100-1R-3.      .      '• '   .   '
 Finish Problems-Solvent Base Coatings. TDtOO-2R-3.
 Safety Considerations in Paint Applications. TD100-
 3R-5.    .         .        "•   .        •  -.-
 OSHA Safety and Health Standards. TD100-4R-4
 Coating Materials. TD100-5R.
'Surface  Preparation. TD100-6.

 Other equipment manufacturers that technical assis-
 tance providers should contact include:
 DeVilbiss   (800)338-4448
 Graco      (800)328-0211

 Internet Links

 The following Internet links can provide valuable
 information on coatings:               -

 The ASTM Home Page
 http://www.astm.org/index.html
 ASTM has developed and published over 10,000
 technical standards which are used by industries
 worldwide. ASTM members develop the standards
 within the ASTM consensus process. Technical
 publications, training courses, and Statistical Quality
 Assurance Programs are other ASTM products; .
 ASTM services include The ASTM Institute for
 Standards Research.              ,

 CAGE  .   •            '    : .
 http://cage.rti.org/
 CAGE (Coatings Alternative Guide) is a tool devel-
 oped by the Research Triangle Institute to assist   ,
 companies or technical assistance providers in select-
 ing appropriate alternative coatings or coatings equip-
 ment.

 Chemical Coaters Association International
 http://www.finishing.com/CCAI/index.html
 The Chemical Coaters Association International is the
 finishing industry's educational arid networking asso-
 ciation.
                                           129

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Corrosion Coatings & Linings Information
Server
http://www.corrosion.com/index.html
Corrosion Coatings & Linings Information Server
Protective Coatings, Linings and Related Re-
sources is devoted to providing up to date,
relevant information about products and services
for the Protective Coatings, Linings, Painting and
Corrosion Industry.

Envirolink
http://www.envirolink.org
EnviroLink is an online environmental information
resource. This non-profit organization unites
hundreds of organizations and volunteers around
the world and provides comprehensive, up-to-date
environmental resources.

EPA'sEnviroSenSe
http://www.epa.gov/envirosense/index.html
Enviro$en$e attempts to provide a single reposi-
tory for pollution prevention, compliance assur-
ance, and enforcement information and data-
bases. Included are pollution: prevention case
studies, technologies, points of contact, environ-
mental statutes, executive orders, regulations, and
compliance and enforcement policies and guide-
lines. A major component of EnviroSense is the
database for "solvent alternatives."

Federation of Societies for Coatings Technol-
 ogy
 http://www2.coatingstech.org/coatingstech/
 An individual member organization of over 7,200
 international professionals in the coatings manu-
 facturing industry. .

 Finishing
 http://wwW.finishing.com
 F5nishing.com contains links to commerce, current
 events, and technical reference materials pertinent
 to anodizing, plating, powder coating, and surface
 finishing. Also located at this site is a link to a
 caller participation area where visitors can pose or
 respond to finishing industry questions.

 The Golden Gate Society for Coatings Tech-
 nology
 http://www.kudonet.com/~paintman/ggsct.htm
 The GGSCT site contains a comprehensive
 bibliography of coating industry issues.
National Paint & Coatings Association
(NPCA)
http://www.paint.org
NPCA is the preeminent organization representing
the paint and coatings industry in the United
States. A voluntary, nonprofit trade association,
NPCA represents some 500 paint and coatings
manufacturers, raw material suppliers and distribu-
tors.

P2Gems
http://www.turi.org/P2GEMS
P2Gems is a search tool for facility planners,
engineers, managers, and technical assistance
providers who are looking for technical process
and materials management information.  The site
contains a database, searchable by keyword or by
four categories: product or industry, chemical or
waste, management tools, or process.

P2Tech
http://www.great-lakes.net/
P2 Tech contains information on the economy,
ecosystem, government, and environmental issues
in the Great Lakes region.  .

The Paint/Coatings Net
http://www.horizonweb.com/pcn/pcnmain.htm
Paint/Coatings Net includes directories of manu-
facturers, distributers, contractors, and consultants
as well as a collection of paint/coatings articles.
The site also contains two discussion areas, a
 coatings clinic and an environmental clinic.

 Pacific Northwest Pollution Prevention Re-
 search Center
 http://pprc.pnl.gov/pprc/p2tech/p2tech.html
 The Pacific Northwest PPRC provides technology
 reviews for manufacturers, researchers and others
 interested in the details of new cleaning technolo-
 gies. Each review includes an overview of the
 technology as well as links to relevant Internet
 sites and bibliographies on each pollution preven-
 tion technology.

 Paint Research Association (PRA) Home Page
 http://www.pra.org.uk
" PRA, the Paint Research Association was estab-
 lished atTeddingtoh, Middlesex, UK in 1926 and
 is now the largest independent research center for
 the coatings industry worldwide. PRA is a mem-
                                              130

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her based organization currently with over 20~0
members.

RadTech Ultraviolet (UV) and Electron (EB)
Beam Curing Home Page    <
http://www.radtech.com/
RadTech International North America is a npn-  ,
profit trade association'with members from
companies that supply UV/EB equipment, raw
materials and formulated' products, and other
indiv iduals interested in or involved in UV/EB  ,
curing technology.          •  .

SAE Home Page
http://www.sae.org/     . .            '    , '
The home page of the Society of Automotive   ,
Engineers is your one-stop resource for all aspects
of vehicle design/engineering, safety, and manu-
facturing information. A non-profit, educational
organization, SAE has nearly 70,00,0 members in
over 80 countries. .   .             .

Society of Manufacturing Engineers
 http:///www.sme.org/
 SME is an international professional society
dedicated to serving its members and the manu-
 facturing community through the advancement of
 professionalism, knowledge, and learning. SME
 has more than 70,000 members in 70 countries.
 The society also sponsors some 300 chapters,
 districts, and regions, as well as.240 student
 chapters worldwide. .     •

 Trade  Associations

 The following trade associations can be contacted
 for more information:

 Air & Waste Management Association
 1 Gateway Center, 3rd Floor   •
 Pittsbury, PA 15222   .
 (412)232-3444  .           ,               •

 American Institute of Chemical Engineers
. 345 East 47th Street
 New York, NY 10017    .
-(212)705-7338

• The Association for Finishing Processes
 OneSMEDrive
 P.O. Box 930                  '-.-••
 Dearborne,MI48121
 (3,13)271-1500
ASTM  ;            •        •••'"'..
100 Barr Harbor Drive
West Conshphocken, PA 19428
(610)832-9500        '       -.'...

Can Manufacturers Institute
1625 Massachusetts Ave. NW, 5th Floor
Washington, DC 20036   ,
(202)232-4677            .

Chemical Coaters Association International
PO Box 54316  -
Cincinnati, OH 45254
(513)624-6767   .              • •   '

Color Association of the United States
409 West 44th St.
New York, NY 1003 6
(212)582-6884

Federation of Societies for Coatings Technology'
492 Norf is Town Road
Blue Bell, PA 19422
(610)940-0777

National Association of Architectural Metal
Manufacturers                       •
8 South Michigan Street, Suite 100
Chicago, IL 60603
(312)782-4951

National Coil Coaters Association
401 N.Michigan Ave.
Chicago, IL 60611-4267
(312)321-6894.           '  •   '  .

National Decorating Products Association
 1050 N.Lindbergh Blvd.        .
 St. Louis, MO 63132-2994         .
 (314)991-3470

 National Paint and Coatings Association, Inc.
 1500 Rhode Island Ave. NW-
 Washington, DC 2005
 (202)462-6272   .          '  .          .

 Paint Research Association
 8 Waidegrave Road
 Teddington, Middlesex
 TW118LD,UK
 +44(181)977-4427     •
                                            131

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Powder Coating Institute
2121 Eisenhower Av.e., Suite 401
Alexandria, VA 22314
(703)684-1770

RadTech International-North America
60 Revere Drive, Suite 500
Northbrook, IL 60062
(708)480-9576

Society of Manufacturing Engineers for Finishing
Processes
1 SME Dr., P.O. Box 930
Dearborn, MI 48121
(3l3)271-1500ext.544

Steel Structures Painting Council
40 24th Street, 6th Floor
Pittsburgh, PA 15213
(412)281-2331

Synthetic Organic Chemical Manufacturers
Association '
1850 M Street NW
Washington, DC 20036-0700
(202)296-8577

Clearinghouses

Center for Environmental Research Information
(CERI)
U.S. EPA           .    '
Cincinnati, OH 45268
(513)569-7562

EPA's Pollution Prevention Information Clearing-
house
401M Street, SWMC 7409
Washington, DC 20460
202260-1023

Great Lakes P2 Information Clearinghouse
One East Hazelwood Drive
Champaign, Illinois 61820
'217333-8940

The Northeast Pollution Prevention Clearing-   .
 house
 129 Portland Street,  6th Floor
 Boston, MA 02114
 617367-8558
Toxics Use Reduction Institute
One University Avenue
Lowell, MA 01854
(508)934-3275       '            •    '

Waste Reduction Resource Center
3 825 Barrett Drive, Suite 3 00
PO Box 27687
Raleigh, NC 27611-7687         '
(919)715-6500

The Pacific Northwest Pollution Prevention
Research Center (PPRC)
1218 Third Ave., Ste. 1205
Seattle, WA 98101         ...
206-223-11151

Technical Assistance Programs with
Expertise in Metal Coating

Illinois Waste Management and Research Center
One East Hazelwood Drive
Champaign, Illinois 61820
(217)3:33-8940

Maine Metal Products Association
190 Riverside Street
Portland, ME 04103-1073
(207)871-8254

Massachusetts Office of Technical Assistance
100 Cambridge Street, Room 2019
Boston, MA 02202
(617)727-3260

MnTAP
1315 5th Street SE, #207   '     -'
Minneapolis, MN 55414
-(612)627-4646
http://www.umn.edu/mntap

North Carolina Division of Pollution Prevention
and Environmental Assistance
PO Box 29569
Raleigh, NC 27626-9569
(919)715-6500
Great Lakes Pollution Prevention Centre
265 N. Front St., Suite 112
 Sarnia^ ON N7T 7X1 CANADA
Tel: (519) 337-3423
                                           132

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Toxics Use Reduction.Institute
University of Massachusetts/Lowell
One University Place
Lowell,'MA 01854
                                             133

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134

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Appendix  B
VOC/HAP  Calculation
Air emissions that result from the evaporation of solvents such as those in paints can be calculated
•using a material balance approach. To calculate the pounds 'of HAPs or VOCs emitted, a firm needs
tO'know:  •   "     . .   '   '                                    .   '. •  '

+• Quantity of product used annually                                               ;
* Total density of the product
* Weight percent HAPs or VOCs     '.'.•'-           "• .   -.
                                                    1    •       .
Calculating the Quantity of Product Used
The quantity of product used can be taken from purchasing records provided a company maintains an
essentially constant inventory. If the firm is disposing of waste materials and has records to show the
amount of HAPs or VOCs .in the waste, that amount can be subtracted from the total used since it was
not emitted into the air.     -;             .

Calculating the Total Density                     .
The total density of the product can be found on the Material Safety Data Sheet (MSDS). Sometimes it
is listed as a specific gravity, calculated by using the ratio of product density/density of water. If specific
gravity is given, multiply by 8.314 pounds per gallon (the density of water),'to get the density of the
product.     '

Calculating Weight Percent       ;
The HAP content in the paint can be found on the MSDS. HAP content may be listed as a volume
percent (vol %) or weight percent (wt %). VOC or solids content also may be listed. If the paint does
 not contain water or exempt VOCs, the VOC content can be calculated from the weight content using
 the following relationship:      ;         .              •                  .'  .

 wt % VOC = 100 - wt % solids         -    '.        •                 .   .-      ' ']

 If the paint contains water or an exempt VOC, the amount of VOCs in the paint is calculated as follows:

 wt % VOC = 1 00 - wt % solids - Wt % water - wt % exempt VOC •  ,  .

 Calculating HAPs and VOCs
                                       135

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136

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Appendix  C
 Economic  Analysis
Selection of a particular paint system (paint and application method) for a specific application depends
primarily upon the products to be coated and production requirements. Before selecting a system, a
comprehensive economic analysis considering the following items should be performed:
                                            1 •           )   •  . •           '.
* Cost per volume of the nonvolatile fraction of the paint         ,
* Transfer efficiency versus paint cost                .  .                                 .
* Relative costs of various coating process equipment             ,          '  ,
•* Energy consumption

The following section provides one method for conducting a comprehensive economic analysis that
considers all four factors. Technical assistance providers can help companies conduct this analysis to
compare P2 options for painting operations.               :

Conventional liquid paints are comprised of both volatile and nonvolatile components. When paint is
applied to the part, the volatile components evaporate, leaving the nonvolatile components to form the '
actual finish. In order to evaluate a coat of an applied finish, one must consider: 1) the nonvolatile
fraction of the paint versus the product cost and 2) the efficiency of the paint application method (i.e.,.
•transfer efficiency).                         ...

Cost per Volume of the Nonvolatile Fraction  of the Paint
The cost of a paint based on its nonvolatile (solid) fraction can be calculated from product information
(generally the product Material Safety Data Sheets [MSDS]). For example, a paint that costs $ 15 per
gallon and contains 33% solids actually costs $15 divided by 0.33 or $45.45 per gallon of solids.'

If a desired film thickness is known, this cost can be further broken down into a cost per applied surface
area using the following equation':

Cost of paint solids per gallon x film thickness in milsx 0.0006233 = paint cost per square foot of  -
applied finish (where 0.0006233'is a unit conversion factor)

Usingmepamtcostof$45.45pergallonofsolidsanda2mil(l mil =-'6.001 inch) finished film thick-
ness, the paint cost per square foot of applied finish (assuming a 100% transfer efficiency) would be:

 $45.54x2x0.0006233 = $0.057 per square foot (ideal)                                   -

 Transfer Efficiency  Versus Paint Cost
 The above calculation gives the minimum or ideal cost of paint per square foot of applied finish
 because it assumes that 100% of the paint product adheres to the part being painted. In order to get an
 actual cost, one must also include transfer efficiency. In most spray painting operations only a portion
 of the product reaches the part to be painted. The remainder (overspray) is collected in the paint booth
 filters or settles to the floor of the paint area. The amount 6f paint reaching the product versus the
 total amount of paint sprayed is referred to as transfer efficiency. A 50% transfer efficiency means
. half the paint adheres to the product and the other half is wasted. To calculate the actual cost of paint
                                          137

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per square foot of applied finish, one must include the estimated transfer efficiency of the paint
operation into trie-above formula as follows:

(Ideal paint cost per square foot x 1 00)/TE = Actual paint cost per square foot
where: TE equals transfer efficiency       .

Using the previous example and a transfer efficiency of 50%, the actual paint cost would be:

($0.057 x  100)/50 = $0.114 per square foot (actual) (IWRC, p. 10-12)
Example                                                                      ..
A small manufacturer of metal cases for consumer electronics currently coats its products with conven-
tional solvent-borne coatings. The firm is considering changing its current coating and application system
to one containing lower VOC content and higher transfer efficiency, and they want to know what the
coverage, total reduction in emissions and materials cost would be for the new system.

VOC Content (pounds per gallon)
Solids Content
Dry Film Thickness (mils)
Equipment Transfer Efficiency
Cost (qallon)
Paint Use (gallons per year)
Existing System
3.5
35%
0.8
28% (air atomized)
$15
4,4.00
Proposed System
2.5
' 30%
<1.0
65% (HVLP)
$20
(to be determined)
 Calculating Material Savings and  Emission Reductions

 Coverage = (paint volume x % volume solids x % transfer efficiency)/dry film thickness

 If the surface to be covered is the same for both production scenarios, then:

 (G2 (gallons) x % VS2.x %TE2)/FT2 (mils) = [(G, (gallons) x % VS, x % TE,)/FT, (mils)]/FT, (mils)
  or
  G2 (gallons) = (G, (gallons) x FT2 (mils)% VS, x % TE,)/(FT2 (mils) x % VS2 x % TE2)

  Where:               '
  G, = amount of coating currently used fora given application
  G2 = amount of coating used in riew method for the same application
  %VS, =%voiume solids of the original coating      -      .
  %VS2 = %volume solids of coating used in new applications method
  %TE*= % transfer efficiency of existing.applicatio'ns method
 , % TE2 = % transfer efficiency of new applications method
  FT, .= film thickness achieved in existing applications method
  FT2 = film thickness achieved in new applications method
                                             138

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 Emissions = -pgint volume used x-VOC content of paint
 or,1
• E (pounds) = G (gallons) x VOC (poGnds per gallon) ,              '•    •   ;
'?Tofa/mafen'a/s cost = paint volume used x cost per gallon of paint

 TMC($) = G (gallons) xC($ per gallon)     .   ,  .                ,

 where:
 c = cost per gallon of alternative coating        /         '   .                      '  :     '
 TMC. = total paint materials cost of new application method    •                          ••   •

 Substituting values, we get: G2 = 4400 x 1x35x287.8 x30x 65 = 2764'gallons  ,           •

 VOC emissions (E) = G (gallons) x VOC (pounds per gallon)

 Current system: 4400-gallons x 3.5 pounds per gallon = 15,400 pounds per year VOC
 ,Prpposed system: 2764 gallons x 2,5 pounds per gallon = 6910 pounds per year VOC

 Reduction in VOC: 8490 pounds per year VOC (NJTAP, p. U)

 Relative Costs of Various Coating Process Equipment
 Because of the various painting requirements present in the broad category of metal manufacturers,
 providing a realistic cost comparison between one paint application method and another is nearly
 impossible. In order to provide some degree of comparative information the following table is offered.
 Cost/Benefit Summary  for Spray Application Methods
Method of
Application
HVLP Spray
Air-Assisted
Airless Spray .
Electrostatic
Spray
Powder
Coating
Capital
Cost
Low
Low
Me.dium
High
Process
Complexity
Low
Low
Medium
High ,
Waste and
Emissions
Medium/High
Medium/High
Medium
Low
Additional
Considerations


Only conductive parts
can be painted
Extensive parts wash-..
ing and a curing oven
are required
NOTE: Capital cost refers to the cost of the system in comparison 'to conventional air spray. The higher the
. process complexity, the higher the associated costs (he., training for employees and maintenance).
  Energy consumption should also be a consideration when selecting a paint and.application method.
  Energy consuming operations include pretreatment (i.e., parts washing), ventilation, and makeup air/
  heat for curing. All three of these factors are directly related to the type of paint and application method
  selected. For comparative purposes, powder coating and waterbprne paints might have higher energy
  requirements because of increased curing demands (I WRC, p. 10-12).    .
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 Appendix  D
 HVLP  Spray  Gun  Purchasing
 Guidelines                                           —
 The Wisconsin Department of Natural Resources
 developed the following list of purchasing consid-
 erations for HVLP guns to help Wisconsin
 businesses identify and evaluate current pollution
 prevention opportunities. Although this list does
 not cover every aspect of equipment selection, it
 includes some of the more important points and
 provides considerations for evaluating HVLP
 equipment.  '               •       ;

 * Would a cup-fed or a tank-fed sprayer be best
 for the applications?             r

 + A cup-fed sprayer is an excellent choice for
 small jobs because it can be loaded with only the
 amount of paint that is needed.

 * A tank-fed sprayer would be more effective for,
 continuous, large volume operations inwhich the
 tank would need to provide a substantial supply of
 paint.

 * Would the firm want to add an air heater to the
 HVLP system?

 * Air heaters may decrease the drying time.

 *• Air heaters will increase the transfer efficiency
 of high solids coating material.            -

 * Air heaters reduce the moisture condensation
 inside the system.     ,                 .-

 * Can the firm adapt any part ofthe existing
 system to the HVLP system or will they need to
 replace the system as a whole?

 * Is the spray equipment warranted for use with
 the material thai you want to apply?

. * Are the electrical controls and components UL
 listed, and do they meet the firm's standards for
. safety at their facility?

 * What is the weight of the spray gun?
«• If the gun is used for an entire shift, the weight
pf the-gun could affect the productivity of the
worker using it.

4 A spray gun made from composite materials
may,be lighter than a gun made from metal.

* What are the available sizes and shapes of the
nozzles that can be used on the spray gun? Are
the nozzles compatible with the material that must
be applied?

* Is the equipment easy to disassemble (and
reassemble) for the cleaning and maintenance of
critical parts?

* Gun washers are considered by some to be an
effective means of cleaning spray equipment..
Some services rent these gun washers and sell the
solvents that are used in them. When the washing
solvent is dirty, the service will pick up the old
solvent for recycling and drop off new cleaner.

+ If you need to supply multiple HVLP spray guns
simultaneously, will the operation of the spray
equipment be affected significantly?

* Can an automatic positioner be added to the
HVLPsystem?

* An automatic positioner holds the spray gun in
the desired position while the material is applied. .
This reduces worker fatigue and improves repro-
ducibility.

•* Are there any local, state or federal health and
safety or environmental quality regulations that
apply to the use of this equipment?

* What are the electrical power requirements for
the HVLP system? Is the system energy efficient?
. (MnTAPb, p. 1-3)
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Appendix  E
Testing
 A variety of quality assurance tests are used on
 cured.paints for characteristics including thickness,
 adhesion, chemical resistance, color match and
 cure. Companies generally select.tests based on
 customer requirements. For example, applications
 that involve high exposure to water and/or weather
 require certain performance standards from the
 coating. Whether the coating supplier provides this
 information or the manufacturer does the tests at
 their facility, the customer must be assured that
 the coating can perform according to specifica-
 tions. This appendix provides brief descriptions of
 tests that are commonly performed by coatef s.

 Thickness
 The thickness of both wet and dry films are often
 measured.

 Wet  Films
. The purpose of measuring wet films is to deter-
 mine if they are sufficiently thick to develop the
 required thickness when dry. Gauges used to
 measure the thickness of wet coatings cut through
 the film. The two most extensively used gauges
. include a wheel gauge and a tooth gauge. Wheel
 gauges are rolled through the wet film to contact
 the base material. A tooth gauge is simply pressed
 into the wet coating to measure the thickness

 Dry  Films
 A wide variety of gauges are used to determine the
 thickness of dry films. Thickness measurements
  can be performed on substrates containing iron by
  using a magnetic "pull-off' type gauge. Magnetic
  attraction decreases in proportion to the coating
  thickness. Pencil and banana gauges are two types
  of pull-off gauges. For other substrates,'microme-
  ters can be used to measure coating thickness.
  Destructive thickness methods include placing a
  piece of tape on the substrate prior to painting,
  removing it, and measuring the difference between
  the tape thickness before and after painting.
 Adhesion
 Adhesion is defined in ASTM Designation D907   •
' as the state in which two surfaces are held to-
 gether by interfacial forces which consist of either
 valence forces or interlocking action, or both. It
 would be difficult or even impossible to measure
 these forces. Often it is difficult to determine the
 true adhesion of a coating due to issues such as
 voids in the surface profile, improper surface
• preparation and surface contamination. Marty
 factors other than substrate and paint properties
 may influence adhesion. As a result, the type of
 test used should be.selected according to the
 -modes, of failure observed in service. The most
 common adhesion tests include film removal and
 cross-hatch. Inertia tests that use vibration to lift
 the coating are rarely used.

 Film  removal
 Tools used to test film removal vary from pocket
 knives to mechanically operated cutting edges,
 blades, or points. Gauges are used on some
 devices to measure the force needed to remove
 the coating.

 Cross-Hatch
 This test requires that two sets of parallel cuts are
 made at 90 degree angles to each other, forming a
 checker-board grid. The percent of paint remain-
  ing on the substrate is estimated. In' some cases,
  additional 45-degree cuts are made.      .     .

  Abrasion  Resistance
  Several properties are involved in the measure-
  ment of abrasion resistance. These include mar
  resistance, hardness, elasticity and tensile strength.

  Flexibility
  Flexibility (bend or impact) is usually measured by
  removing a piece of tape applied prior to painting..
  ASTMD-3359 provides details about this simple
  test, including a rating scale for evaluating results.
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It is critical to perform this test consistently. The
actual method may vary, but the procedure must
be performed identically every time.

Hardness
A wide variety of devices are used to measure
the hardness of paint films, including scratch or
pendulum mechanisms.

Scratch
Scratch tests on paint films maybe performed
using mechanically operated styli or knives. The
pencil hardness test is also widely used. In this  .
test, pencil lead with specified hardness is pushed
against the paint. The hardest lead that does not
mar the paint is considered the paint hardness.
Pencils are available in 17 different grades of
hardness ranging from 9H, the hardest, to 6B, the
softest (SME, p. 30-3). As with other subjective
tests, procedures must be followed consistently so
test results are meaningful.

 Extent of Cure

 (Solvent Resistance)
 Extent of cure can be determined via hardness
 testing or a "solvent rub" test. The solvent rub test
. involves rubbing the cured coating a prescribed
 number of times with a cloth saturated with a
 specific solvent. If no color appears on the cloth,
 the paint is considered cured.

 Weather Resistance
 Water and weather resistance  can be measured in
 a variety of ways. Immersion, humidity resistance,
 and accelerated weathering tests are typical
 methods. Accelerated weathering tests combine
 UV light exposure with elevated temperatures and
 humidity or salt sprays. In addition to predicting
 field performance, the accelerated weathering test
 used evaluates different coatings' performance.
 It is an effective screening  tool for choosing
 alternate formulations.

  Color Matching
  Color matching is challenging because it requires
  the manipulation of many variables which contrib-
  ute to the test's outcome. Reflected light is the
  basis for interpreting color. Light sources (sunlight
  or specific artificial sources) vary in intensity, thus
the amount of reflected light may vary. Conduct
color matching, whether visual or instrumental,
under several light sources. The Munsell system
and the Cffi. systems are commonly used and
employ three different light sources to determine
color ( KSBEAP, p. 26-27). For a summary of
various tests, see the table below.

Summary of Paint Tests (KSBEAP, p. 27)
Attribute Measure
Thickness
Flexibility
Paint Adhesion
Hardness
Extent of Cure
Water or Weather
Resistance
Color Matching
Test
Pencil or banana gauge
Micrometer
Tape thickness
Bend or impact
Tape adhesion
Pencil hardness
Solvent rub
Immersion
Humidity resistance
Accelerated weathering
Munsell or CIE
                                          144

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Appendix  F
Glossary=
Acrylic : A resin resulting from the polymeriza-
tion of derivatives of acrylic acids, including
esters of acrylic acid, methacrylic acid, acryloni-
trile, and their copolymers. Acrylics are also used
in powder coatings in their thermoplastic form.

Active solvent: A liquid which dissolves a.binder.

Additives: Any substance added in small quanti-
ties to another substance, usually to improve
properties. Examples of additives include plasticiz-
ers, fungicides, and dryers.

Adhesive: A substance capable of holding materi-
als together by surface attachment. Various
descriptive adjectives are used with the term
adhesive to indicate certain characteristics: physi-
cal (liquid adhesive, tape adhesive), chemical type
(silicate adhesive, resin adhesive), materials
bonded (paper adhesive), and conditions of use
 (hot-set adhesive).                     '

 Air-assisted airless spray: Paint spray application
 system using fluid pressure to atomize the paint
 and low pressure air to adjust the shape of the fan
 pattern.

 Air-bearings: A stream of air used to support a
 spinning shaft. Air bearings have limited load
 carrying capacity but require no lubricants,,

 Air-dried coatings: Coatings which are not
• heated above 194°F (90°C) for coating or drying.
 In the South Coast Air Quality Management .
 District, curing also must be done below (rather
 than at or below) 194°F (90°C) to qualify as air
 dried. Air-dried coatings also include forced-air
 dried coatings.  	

 Air-dryers: Used to remove moisture.from
 compressed air. Dryers have three basic styles of
  operation: 1 .deliquescent types have disposable .
  drying agents and tend to be marginally effective
  for painting; 2. refrigerated dryers cool the air to
 condense and remove the water. Most paint
 systems use this type; 3. desiccant types have a
 double bed dryer and are able to achieve the
 lowest dew point air. The beds are alternately on-
 stream and back-flushed to regenerate their
 moisture absorbing qualities. Some plants with
 critical finish requirements use this style of dryer
 to reach dew points of-40°F.

 Air knife: A slotted jet of compressed air quickly
 blows superfluous water from parts, often before
 they enter a dryoff oven.

 Airless spray: A paint spray application system  .
 using high fluid pressure to atomize paint by
 forcing it through a small orifice.

 Air spray: A paint spray application system using
 air at high velocity and pressure to atomize the
 paint.

 Air turbine: 1: Electric motor driven fans that
 create volumes of relatively low-pressure atomiz-
 ing air for spraying. Their output is referred to as
 turbine air; 2. An air-driven-precision fan that is
 used to spin a paint atomizing disk or bell head.

 Aliphatic solvent: A solvent comprised primarily.
 of straight chain hydrocarbons, including mineral
 spirits, kerosene, and hexane. These solvents are
 characterized as volatile organic compounds.

 Alkali: Any substance that neutralizes acids.
 Alkalis are helpful in aqueous cleaning to speed
. soil removal and suspension. Alkali is synonymous
 with caustic.

  Alkyd: A binder based on resins formed by the
  condensation of polyhydric alcohols with polyba-
  sic acids. They may be regarded as complex
  polyesters (Thermoset).

  Amino resins: Resins used to crosslink polyes-
  ters, epoxies, acrylics, and alkyds to enhance their
  durability.
                                             145

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Amperes (AMPS): An electrodynamic unit of
measure for the quantity of current in a steady
electric flow.

Anode: The electrode at which chemical oxidation
takes place. In electrodeposition (E-coating) the
anode is indicated on diagrams fay the positive (+)
marking.

Anoltye: The water used to flush solubilizer
molecules that form inside an ejectrocoating anode
box. If used to flush a cathode box, it is termed  •
catholyte.

Aromatic solvents: Hydrocarbon solvents which
contain an unsaturated ring of carbon atoms,
including benzene, naphthalene, anthracene and
their derivatives. Toluene (toluol) and xylene
(xylol) are commonly used aromatics. These
solvents are characterized as volatile organic
compounds.

Atomization: The formation of tiny liquid
droplets during the spraying of coatings.

Autodeposition: Dip coating application method
which depends on a chemical reaction to plate out
the coating film.

Autodeposition (autophoretic): A precipitation
reaction of an organic resin that occurs by the
action of an acid etching a metallic substrate. The
ions of the oxidized metal codeposit with the vinyl
emulsion resin.

Azeotrope: A liquid mixture that distills with out
change in composition. Azeotropes are character-
 ized by a constant minimum or maximum boiling
 point which.is lower or higher than any of the
 components.                            '

 Baked coatings: Coatings that are cured or dried
 at or above an oven air temperature of 194°F
 (90°C).

 Barytes: Colorless crystalline solids, which are a
 form of barium sulfate (also called barite). Barytes
 are used as an extender pigment in primers and
 coatings.
Bells: A rotating head that is shaped to deliver
paint forward in a circular pattern. The bell may
be directed at any angle and be moved on robots
orreciprocatorsjustasspray'gunsare.  "  .

Bentonite: A type of clay derived from volcanic
ash, which is often used as a paint pigment.

Binder: The solid (non-volatile) material in a
coating that binds the pigment and additive
particles together to form a film. In general,
binders are resins.

Biocide: A chemical agent capable of killing
organisms responsible for microbial degradation.
Biocides are sometimes added to wqterborne
coatings.

Bituminous coating: An  asphalt or tar compound
used to provide a protective finish for a surface.

Bleeding: Discoloration which occurs when '
colorants frdm a lower coat diffuse into a surface
coat.

Blistering: The formation of hollow bubbles in
the paint film caused by air, moisture, or solvents
trapped under the film.

Blocked isocyanates (blocking agent): Isocyan-
ates, normally extremely reactive with water, can
only be used in waterborne coatings if they can be
prevented from reacting before the water is baked'
out of the paint film. This is done by capping or
blocking the isocyanate group with a thermally
decomposable chemical.  In a bake oven, the water
evaporates! the chemical  cap decomposes and the
 isocyanate crosslinks the paint. Blocked isocyan-
 ates are often employed for E-coat curing.

 Blocking: Undesirable sticking together of painted
 surfaces when pressed together under normal
 conditions. Sticking or blocking can be reduced by
 anti-block paint additives.

 Blooming:  Powder-like deposit forming on the
 surface of the film often resulting from partial
 dissolving and redepositing of pigment by a
 solvent component.
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 Blushing: Whitish, milky area which develops on
.the film'and may be caused by absorption of
 water vapor by the drying film.

 Bounce-off, bounceback: Paint droplets from
 air-ato.mized application that rebound or bounce
 away from the surface due to the blasting effect of
 the air.

 Brush coating: Manual application of coatings   •
 using brushes and rollers.

 Bulk coating: The painting of large masses of
 small unchangeable parts by a variety of possible
 techniques such as dip-spin and dipping.

 Burn-off ovens: A paint stripping method accom-
 plished by combustion of the coating in gas-fired,
 burn-off ovens in which high temperatures are
 controlled by. injecting of water spray into the
 oven.

 CARC: Chemical Agent Resistant Coatings. The
 polyurethane-based coatings are highly crosslinked
 to resist chemical attack. CARC is often used on
 military equipment that might become contami-
 nated by nuclear, biological, or chemical sub-
 stances.

 Cathode: The cathode is defined as the electrode  :
 at which'chemical reduction takes place. In
,electrodeposition (E-C6ating) the cathode is
 indicated on diagrams by the, negative (-) marking.

 Caustic: A substance that neutralizes acids.
 Caustics are used in aqueous cleaning to speed soil
 removal and increase soil suspension. Caustic is
 synonymous with alkali.                     :

 Cellosolve: The generic term for the solvent
 family of mono-alkyl ethers of ethylene glycol.
 For example,  a widely-used solvent is butyl
 cellosolve, which chemically is ethylene glycol
 monobutyl ether.

 Centrifugal coater: see dip-spin coater

 Chalking: The degradation of a paint film by
 gradual erosion of the binder, usually due to
' weathering.
Checking: Slight breaks in the film that do not ..'
penetrate to the substrate surface. If the substrate
surface is exposed it is called cracking.

Chipping: Total or partial removal of a dried paint
film in flakes by damage or wear during service. •

Chlorinated solvents: Organic solvents that
contain chlorine.  Examples include 1,1,1-
trichloroethane and methylene^chloride. These
solvents are characterized as volatile organic
compounds. Their use is regulated and heavily,
restricted.              ,                  ,

Coating: A liquid or mastic composition which is
converted to a solid protective, decorative, 6r
functional adherent film. The South Coast Air
Quality Management District defines coatings as
materials which are applied to a surface and
which form a continuous film in order to beautify
and/or protect the surface.

Coating line: Coating lines are all operations
involved in the application, and/or drying of
surface coatings. However, this definition does not
specificly delineate what separates coating lines in
a source, especially when a single oven may cure
parts from multiple spray booths. For most rules,
where the exemption level of the rule is not related
to the volume of coating applied per coating line,
this definition does not apply.

Cobwebbiag: The tendency of spray paint to
form strands rather than droplets as it leaves the
spray gun. Cobwebbing may be caused by too
volatile a solvent or too little air pressure.

Continuous coater: An enclosed automatic spray !
booth that recovers and reuses oversprayed paint.
A continuous coater is suitable for coating large
volumes of similarly-sized parts.

Conversion coating: A chemical or electrochemi-
cal treatment of a metal surface to convert it to
another form, which provides an insulaiting barrier
of exceedingly low solubility between the metal
and its environment, and is an integral part of the
metallic substrate. Examples are phosphate coating
of steel and zinc and chromate anodizing of
aluminum.
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Cosolvents: Water-miscible organic solvents.
Waterborne paints frequently require cosolvents in
addition to water for easier manufacturing and
improved application properties.

Cracking: The splitting of a dry paint film, usually
the result of aging. This includes: hair cracking,
checking, crazing, and alligatoring (crocodiling).

Cratering: Small round depressions in a paint film
which may or may not expose the underlying
surface.

Crawling: A defect in wet paint or varnish film  .
where it recedes from small areas of the surface,
leaving them apparently uncoated. Crawling is
caused by an-incompatible film on the surface.

Crazing: The formation of fine surface cracks,
often as a network, which do not penetrate to the
underlying surface.

Crosslinking: The setting up of chemical links
between the molecular chains of a resin to form a
three-dimensional network polymer system.
Crosslinking generally toughens and stiffens
coatings.

 Cup gun: A spray gun used with a siphon cup.

 Cure: Using heat, radiation, or reaction with
 chemical additives to change the properties of a
 polymeric system into a more stable, usable
 condition. For liquid coatings, it is the process by
 which the liquid is converted into a solid film.

 Current density: A measure of the total electrical
 flow across a given area, frequently expressed in
 units of amps/square foot.

 Cyclone separator: A funnel-bottomed enclosure
 that rapidly moves particulate-laden streams of air
 in a circular path. As the relatively high mass of
 particles are thrown to the sides of the enclosure,
 they slide down through the funnel'into a con-,
 tainer for reuse. Cyclone separators are commonly
 used for powder coating applications.

 •Deionized water: Water resulting from the
  removal of contaminants by a double-bed ion
  exchanger. The ion exchanger replaces positive.
impurity ions with H+ (hydrogen) ions and
negative impurity ions and OH-(hydroxide) ions.
The hydrogen ions and hydroxide ions then
combine to form HOH (H20). Deionized water is  '
comparable in purity to distilled water but is
much less costly to produce.

Diluent: Liquids which increase the capacity of a
solvent for the binder. Diluents cannot dissolve the
binder themselves, but are used to control viscos-
ity, flash time, or cost. While true solvents can be
added in unlimited amounts to lower paint viscos-
ity, it may be more economical to lower viscosity
With less costly diluent solvents. When added to a
prepared paint, a diluent will lower the viscosity
just as effectively'as a true solvent. However, if
too much diluent is added, the resin will separate
out of solution and the paint becomes unusable.

Dip coating: The process in which a substrate is
immersed in a solution (or dispersion) containing
the coating material and withdrawn.

Dip-spin icoater: Bulk painting of small and
unchangeable parts accomplished by dipping a
mesh basket of parts, followed by rapid rotation of
the basket to remove excess paint. Parts from the
dip-spin cpater Eire dumped onto a belt for curing.

Disks (discs): Rotating heads that deliver paint
using a horizontal 360 degrees motion and an
omega loop conveyer line. A disk is usually
 mounted horizontally on a vertical reciprocator.

 Dispersion coating: A type of coating in which
 the binder molecules are present as colloidal
 particles and spread uniformly throughout the
 formulation as a stable mixture.

 Doctor blade: Device used to prepare paint and
 varnish films of even and predetermined thick-
 nesses.

 Drier: An additive which accelerates the drying of
 coatings.

 E-coating (electrodeposition): A dip coating
 application method where the paint solids are
 given an electrical charge opposite to the part
 being coated. In this method, which closely
 parallels electroplating, paint is deposited using
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direct electrical current. The electrochemical
reactions that occur cause water-soluble resins to
become insolubilized onto parts which are elec-
trodes in the E-coating paint tank. Subsequent
resin curing is required.                    y-

Eductor: Nozzles located along E-coat return
.headers, and spaced laterally at intervals across the
tank. These nozzles help to agitate the paint and
prevent settling of pigments, which results in
cleaner film deposits.          ,

Electrostatic spray: Method of spray application
of coating where an electrostatic potential is
created between the part to be coated and the
paint particles.    .    '   .      .

Emulsion: A two-phase liquid system in which
 small droplets of one liquid (the internal phase) are
 immiscible in, and are dispersed uniformly
 throughout, a second continuous liquid phase (the
 external phase). This contrasts with latex, which
 consists of solids dispersed in a liquid.

 Emulsion paint: A coating comprised of an
 emulsion of a resin binder in water.

 Enamels: Topcoats which are characterized by
 their ability to form a smooth surface; originally
 associated with a high gloss, but may also include
 a lower degree of gloss. Also a class of substances
 having similar composition to glass with the
 addition of stannic oxide, or other infusible
 substances to render the enamel opaque. Can be
 used to describe a coating which forms a film
 through chemical union of its component mol-
 ecules during curing. In shop termiriology can be
 used to describe paint which is no longer a
 lacquer. All paints, powder or liquid, that form
 crosslinking chemical bonds during curing are
 considered enamels. The majority of industrial
 finishes fall into this category.

  Epoxies: Binders based on epoxy resins. Epoxy
 'crosslinking is based on the reaction of the epoxide
  groups with other materials such as amines,
  alcohols, phenols, carboxylic acids, and unsatur- -
  ated compounds. Also used as a thermoset
  powder coating.
 Etching: A chemical solution used to remove a
 layer of base metal to prepare a surface for   ,
 coating or binding.

 Etching filler: Coatings that contain less.than
 23% solids by weight, and at least 0.5% acid by
 weight, and are used instead of applying a pre-
 treatment coating followed by a primer.

 Exempt compounds: Hydrocarbon compounds
 excluded from the definition of volatile organic
 compound, as defined by the U. S. Environmental
 Protection Agency, on the basis that these com-
 . pounds have negligible contribution to tropo-
' spheric ozone formation. Acetone is an exempt
 compound.

 Extender (pigments): White powders used to
 give body to the coating.       >

 Fading: The loss of color in a pigmented coating
 film, over time, following exposure to light, heat,
 etc.    '••'-.

 Faraday cage: Electrostatic application causes
 paint particles to be attracted to the nearest
 grounded object. This attraction force is often
 strong enough to pull paint particles out of their
 intended flight direction. Recessed areas on parts
 often receive insufficient paint coverage since they
 require a slightly longer path for paint particles. As
 a result, these Faraday Cage areas may need
 touch-up painting with non-electrostatic spray.

 Faraday cage effect: The phenomenon by which
  charged particles are prevented from entering
  recessed areas during the electrostatic application
  of coatings.

  Fatty edge: An.excess bead of paint that forms on
  the bottom edges of parts when they are in the
  drippage zone following dip or flow coating.

  Film: One or more layers of coating covering an
  object or surface.

  Fisheye: A paint defect resulting in a pattern of
  small surface depressions' or craters in the wet
  film, often caused by surface contamination such
  as oil or silicone materials.
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Flash point: The lowest temperature of a liquid
at which it gives off sufficient vapor to form an
ignitable mixture with air.

Flash-off time: The time required between
application of wet-on-wet coatings or between
application and baking to allow the bulk of the
solvents to evaporate. In baked coatings, the flash-
off time helps to prevent solvent boil off and film
blistering.

Flat coatings:  Coatings with a gloss reading of
less than 15 on an 85-degree meter or less than 5
on a 60-degree meter. This definition is usually
found in architectural, coating rules.

Flocculation:  The formation of loose clusters of
dispersed pigment particles in liquid coatings.

Flooding, floating, or mottle: Tendency of
pigment particles to separate and concentrate in an
area such as the surface.

Flow coating:  A coating application system where
paint flows over the part and the excess coating
drains back into a collection system.

Fluidized bed: Finely divided powders can be
made into a fluid-like state by passing air through
the porous plate bottom of a powder hopper. This
permits powder particles to.be used in dip tanks
and to be transported in a manner similar to
liquids.

Flushable electrode: An anode in cathodic E-
coating placed inside a semi-permeable membrane
enclosure. Excess solubilizer generated at the
anode can be continuously removed by water
pumped into the bottom of the enclosure.
Flushable electrodes in anodic E-coating can also
be used (but rarely are needed) for the cathode.

Free radical polymerization: Reactive electrons
that chemically bond to adjacent molecules and
produce a cured paint film. Certain organic
compounds will form highly reactive electron
configurations by the action of UV light (or other
activation sources). These reactive species are
called free radicals because, to an extent, 'free'
electrons are available for bonding.
 Fusion: The melting of a powder coating into a
 solid film.

 Grain refiners: Agents used in water rinses prior
 to zinc phosphating or in the zinc phosphatizing
 bath itself to produce smaller crystals. Finer grain
 zinc phosphate crystals provide superior corrosion
 resistance and paint adhesion.

 Ground (electrical ground): An object so
 massive that it can lose or gain overwhelmingly  .
 large numbers of electrons without becoming
 perceptibly charged.

 Halogenated hydrocarbons (halogenated
 solvents): Formed by substituting one of the
 halogen elements (chlorine, bromine, or fluorine)
 into a chemical compound to change both the
 physical and chemical nature of the compound..

 Heat-resistant coatings: Designed to resist
 degradation upon continuous or intermittent
 exposures to a predetermined elevated tempera-
 ture. A San Diego Air Pollution Control District
 rule stipulates that the coating must withstand
 temperatures of 400°F during normal use as
 determined by ASTM Method D-2485.

 High boilers: Solvents with a boiling point above
 212°F (tail-end solvents). These solvents usually
 evaporate during baking.

 High-solids: Solvent-borne coatings that contain
 greater than 50% solids by volume or greater than
• 62%(69% for baked coatings) solids by weight.

 High temperature coatings: Coatings certified to
 withstand a temperature of 1000°F for 24 hours.

 High volume low pressure spray: Spray equip-
 ment used to apply coating by means of a gun
 which operates between 0.1 and 10.0 psig air
 pressure. The high volume of air is produced by a
 turbine.

 Hot water curing: A curing procedure which
 involves immersing parts in 180°F water. Hot
 water curing is faster than oven curing for parts
 that act as a large heat sink, but is normally not
 used since it results in reduced corrosion resis-
 tance.
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Hydrocarbon solvent: An organic compound
consisting exclusively of the elements carbon and
hydrogen. They are principally derived from
petroleum and coal tar, arid include aliphatic,
aromatic, and napthenic solvents.

Hydroxides: The chemical opposites of acids.
Also known as caustics and alkalis.'Examples are
sodium hydroxide and potassium hydroxide.

Hygroscopic: A material property defined by the
ability of a substance to readily absorb moisture
from the air. Hygroscopic materials, such as silica
gel and calcium chloride, arejised as desiccants.
Thinly spread deposits of hygroscopic materials   .
can absorb enough water to completely dissolve.

Inhibitor: A chemical additive that retards
undesired chemical reactions such as corrosion,
oxidation, drying, and skinning.

Initiator: A chemical used to help start a chemical
reaction such as polymerization. Its action is
similar to that of a catalyst, except that it is usually
consumed in the reaction.

Inorganic polymers: Substances whose principal
structural features are made up of homopolar
interlinkages between multivalent elements other
than carbon. This does not preclude the presence '
of carbon-containing groups in the side branches,
or in interlinkages between principal structural
members. Examples of such polymers are ethyl
and butyl silicates, mica, clays, and talc.

Ionized air cloud: A cloud of air molecules that
have picked up excess electrons around the tip of .
an operating electrostatic spray gun. The elec-
trons from the power pack flow off the end of the
needle electrode at the gun tip. When paint
droplets pass through the ionized air cloud they
accumulate electrons that enable electrostatic
 attraction of the droplets to parts being coated.

 Isocyanate: A compound containing the func-
 tional group -N=C=O. Isocyanates are crosslinked
. with hydroxyls to form polyurethanes.

. Kick-out: .The portion of binder that comes out of
 solution as small lumps.
Lacquer: Coating composition based on syn-
thetic thermoplastic film-forming material dis-
solved in organic solvent and dried primarily, by
solvent evaporation. Typical lacquers include  .
those based on nitrocellulose, other cellulose
derivatives, vinyl resins, and acrylic resins.

Latent solvent: A liquid which cannot itself
dissolve a binder but which increases the tolerance
of the coating for a diluent.

Latex: Stable dispersion of polymeric solids in an
aqueous medium.
                                . -          x

MEQ (milliequivalents): The concentration of E-
coat solubilizer in the bath.,

MHO: Unit of conductance equal to the reciprocal
of the ohm.

Molecule: The smallest particle of a substance
that retains all the properties of that substance and
is composed of one or more atoms. Water, for
example, consists of molecules having 2 hydrogen
atoms and 1 oxygen atom. The chemical formula,
H2O, indicates the composition of a water mol-
ecule. Organic polymers often have many thou-
sands of atoms per molecule.

Molten salt bath: A mixture of inorganic salts
melted at temperatures between 650° and 900°F.
Painted items immersed in these are rapidly
stripped by combustion of the paint.

Nitrocellulose:, A binder (resin) based on a
polymer from cotton cellulose. Nitrocelluloses
were primarily used in lacquers, and were widely
used from the 1920's to the 50's on automobiles.
                                     v
OHM: A standard unit of resistance to electrical
flow.    .      .

Ohmeter: A device that measures (in units of
ohms) electrical resistance in a circuit.

 Oil base: Coatings which form films through .
 crosslinking of unsaturated plant oil (drying oils) in
 the presence of oxygen.

 Omega loop: The conveyor for rotating disk
 paint applicators that is shaped to produce a
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circular path around the vertically oriented disk to
deliver paint from all 360 degrees of its circum-
ference. The term was derived because the
shape of the conveyor resembles the capitalized
form of the Greek letter.

Orange peel: An irregularity in the surface of a
paint film resulting from the inability of the wet
film to level out after being applied.

Overbake or overcure: Exposure of the coating •
to a temperature higher or for a longer period of
time, or both, than recommended for optimal
curing; the condition may adversely affect the
appearance and properties of the coating.

Overspray: Any portion of a spray-applied
coating which does not land on a part.

Oxygenated solvents: Volatile organic com-
pounds which contain oxygen in addition to
carbon and hydrogen. Includes alcohols, esters,
ketones, and ether-alcohols.

Peeling: Failure of a coating film to maintain
adhesion with its substrate. Sheets or ribbons of
the film detach from the substrate. The condition
results from contaminated surfaces or excessive
differences in polarity and thermal expansion
characteristics between the surface and the film.

Permeate: The output from ultrafiltration, also
called ultrafiltrate.

pH: The measure of the acidity or alkalinity of a
solution and defined as the logarithm of the
reciprocal of the hydrogen-ion concentration of a
solution. The scale ranges from 2 for highly acidic
solutions to 14 for highly basic or alkaline solu-
tions. Neutral solutions have a pH of 7. Because
the scale is logarithmic, the intervals are exponen-
tial.

Phenolic resins: Resins formed by condensation
of phenols and aldehydes.

Phosphating: A pretreatment for steel or certain
other metal surfaces by chemical solutions con-
taining metal phosphates and phosphoric acid as
the main ingredients. A thin, inert adherent,
corrosion-inhibiting phosphate layer forms which
serves as a good base for subsequent paint coats.

Pigment: Finely ground insoluble particles
dispersed in coatings to influence properties such.
as color, corrosion resistance, mechanical strength,
hardness, durability, etc. Particles may be natural
or synthetic, and inorganic or organic.

Polar: Descriptive of molecules where the atoms
and their electrons and nuclei are so arranged that
one end of the molecule has a positive electrical
charge and the other end of the molecule has a
negative electrical charge. The greater the distance
between the two charged ends, the higher the
polarity. Polar molecules ionize in solution and
impart electrical conductivity.                .

Polyester: A polymer in which the monomer units
are linked by the functional group -COO-. Polyes-
ter has been used as thermoplastic powder  •
coating, and in the following thermosetting powder
coatings: epoxy polyester hybrid powder, urethane
polyester powder, and polyester TGIC powder.

Polyethylenes: Thermoplastic resins composed of
polymers of ethylene (CH2CH2). Polyethylenes
are normally translucent, tough, waxy solids that
are unaffected by water and a large range of
chemicals. Frequently used in powder coatings.

Polymers: A high molecular weight organic
compound, natural or synthetic, with a structure
that can be represented by a repeated small unit,
or mer.

Polypropylenes: Tough lightweight thermoplastic
resins composed of polymers of propylene
(CH3CHCH2). They are commonly used in
powder coating.

Popping: Eruptions in a coating film after it has
become partially set, causing craters to remain in
thefilm.

Pot life: The length of time a coating material is
useable after the original package is opened or
after a catalyst or other ingredient is added.

Powder coatings: Any coating applied as a dry
(without solvent or other carrier), finely divided
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'solid which adheres to the substrate as a continu-
ous film when melted and fused.

Power-and-free conveyor: A separate pusher
chain unattached to paint hooks and riding freely
on a separate-support beam (as distinguished from
a continuous power conveyor). This conveyor
allows parts spacing to vary and parts to be held
stationary even when the pusher chain is moving.

.Power conveyor (continuous): Electrically
driven cables or .chains mechanically attached to
hoods which are used to hang parts to be painted.
The conveyor is used to carry parts through the
painting process. When the line is operating, all
individual hooks on the line will continue to move
and maintain theirspacing.                      •_

Precursor: A chemical compound which is
released into the atmosphere, undergoes a chemi-
cal change, and leads to a new (secondary)
pollutant. Volatile organic compounds are precur-
 sors to  ozone.

 Pressure pot: Various-sized paint tanks containing
 delivery tubes which extend to the bottom of the
 tank. These tanks are pressurized with com-
 pressed air to force paint to the application device.

 Primers: Coatings which are designed for applica-
 tion to a surface to provide a firm bond between
 the substrate and subsequent coatings.

 Reactive diluent: A liquid which is a VOC during
 application, and through chemical reaction, such
 as polymerization, 20% or more of the VOC
 becomes an integral part of the finished coating.

 Reciprocatqr: An automated device which moves
 a paint-applying tool in alternating directions along
 a straight or slightly curved horizontal or vertical
 path.

 Resin: The polymer (plastic) component of a
 paint that cures to form a paint film. Also known
  as binder or vehicle.

  Retarders: Solvents added to a coating to slow
 . down a chemical or physical change, such as the
  rate of evaporation.
Reverse osmosis:  In reverse osmosis, high
pressures are applied to force water out of the
concentrated solution, often to obtain pure (or
purer) water. Solvent is driven through a semi-
permeable membrane separating solutions of
different concentrations.

Ringing: The occurrence of circular spots in a
sprayed repair area (spotting).

Roll coating: .Process by which a film is applied
mechanically to sheet or strip  material.

Rusting (face and/or scratch): The appearance
of metal oxidation (corrosion) on the surface of
damaged paint.

Sagging: The downward flow of a coating film as
a result of the film being applied too heavily or
fluid-like.

Sandscratch swelling: A paint defect where
solvent from a repair coat soaks into scratches in
the initial coat and causes paint swelling.

Sealers: A liquid coat applied to a porous sub-
strate such as wood or plaster, to prevent the
substrate from absorbing subsequent coatings.

Shelf life: The length of time a coating may
normally be stored without losing any chemical/
physical properties. Manufacturers typically
specify the shelf life.     -

Silicone release: A coating which contains
 silicone resins and is intended to prevent food "
 from sticking to metal surfaces such as baking
 pans.

 Silicones: Resins consisting of silicon-oxygen
 linkages, unlike organic resins which contain
 carbon.

 Silking: A surface defect which results in parallel'
 flew lines in the paint film.               '

 Siphon cup (suction cup):'When a special air
 spray tip is employed; a partial vacuum is created
 by the atomizing air just outside the fluid orifice. •
 As a result, atmospheric pressure on the paint in a
 container connected to the fluid line(such as a
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siphon cup) will force paint out of the container
into the fluid line. The term siphon is actually a
misnomer; suction is a more accurate description
of the action.

Skinning: The formation of a surface skin on
coating liquids formed by the coating reacting with
air or rapidly loosing solvent.

Slitting: Cutting wide coils of roll-coated materials
into narrower widths.

Solubilizer: Compound that forms polar polymer
ions when mixed with water-insoluble resins.   .
Since water is a pojar solvent and resins are
usually non-polar, the resins must be treated to
increase their polarity if they are to be used in
waterbome paints.

Solution paint: Resin molecules fully dissolved
by solvents in the paint.

Solvency: The degree to which a solvent holds a
resin or other paint binder in solution.

Solvent: The liquid or blend of liquids used to
dissolve or disperse the film forming particles in a
coating which evaporate during drying. A true
solvent is a single liquid which can dissolve the
coating. The term solvent is often used to describe
terpenes, hydrocarbons, oxygenated, ftirans,
nitroparaffiins, and chlorinated solvents.

Solvent-borne: Coatings in which volatile organic
compounds are the major solvent or dispersant.

Specific gravity: Weight of a given volume of any
substance compared with the weight of an equal
volume of water. Also known as relative density.

Static electricity (electrostatics): Electrons
temporarily removed from various items can cause
static charges. Whatever has excess electrons has
a negative charge; the object from which electrons
have been taken will be positively charged.
Electrons will tend to jump from a negatively
charged object to a positively charged object.

Stencil coating: Ink or other coating which is
rolled or brushed onto a template or stamp
in order to add identifying letters and/or numbers
to metal parts and products.

Surface tension: The energy required to expand
a liquid surface by one unit area. Liquids reduce
their surface area to bring intermolecular attrac-
tive forces into equilibrium. A low degree of
surface tension is preferred for liquid coatings to
maximize minimize wetting and spreading and
minimize edge-pull'and fish-eye effects.

Surfacer: Easily sanded coating used to fill
surface irregularities.

Terpene solvents: Volatile organic compounds
obtained from pine tress and are the oldest
solvents used in coatings. Includes turpentine,
dipentene, and pine oil.

TGIC (triglycidyl isocyanurate): A complex
chemical used to crosslink paint, especially
polyester powders, to increase exterior durability.

Thermoplastic: Resin capable of being repeatedly
softened by heat and hardened by cooling. These
materials, when heated, undergo a substantial '
physical, rather than chemical, change. Thermo-
plastic resins can be completely dissolved with
appropriate solvents.

Thermoset: Resin that, when cured by application
of heat or chemical means, changes into a sub-
stantially infusible and insoluble material. Thermo-
setting resins will soften but will not dissolve in
any solvent.

Thinning: The process of adding volatile liquid to
a coating to reduce its viscosity. This liquid may
be a solvent, diluent or a mixture of both. Thin-
'ning may also be called reducing or "adding m'aike-
up solvent".

Thixotrope: Substance that temporarily causes
high paint viscosities by forming loosely-held
three-dimensional particle networks within paint
fluids. Agitation of the paint by stirring, pumping,
spraying, etc., quickly destroys the networks and
viscosity drops sharply. When agitation is halted,
the networks rapidly reform and paint viscosity
rises again.
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 .Thixotvopy. The tendency for the viscosity of a
 liquid to be shear-rate dependent. When a liquid is
 rapidly shaken, brushed, or otherwise mechani-
 cally disturbed the viscosity decreases rapidly.

 Throwing power: The ability of electro-deposited
 coatings to cover interior surfaces.

• Topcoat: The final coating film or multiple layers
 of the same coating film applied to the surface.

 Touch-up: The portion of the coating which is
 incidental to the main coating process but is
 necessary to cover minor imperfections.

 Transfer efficiency: The ratio of solids adhering
 to a surface, to the total amount of coating solids
 used in the application process, expressed as a    ,
 percentage.

 Undertake or undercure: Exposure of the
 coating to a temperature lower or for a shorter
 period of time, or both, than recommended for
 optimal curing; the condition may cause tackiness,
 softness, and inferior film durability.

 Ultrafiltation: Ultrafiltration uses low-pressure
 membrane filtration to separate small molecules
 from large molecules arid fine particulates. For
 example, E-coat rinse water is extracted from the
  paint bath by ultrafiltation.        '         .

  Ultrafiltrate: The output from an ultrafiltration
  unit; also called permeate.

  Ultrasonic cleaning: Vibrational frequencies
  slightly higher than those audible used to agitate
 ' immersion cleaning tanks. Microbubble formation
  in the liquid accelerates dislodgement of soils.

  Undercoats: Coatings formulated and applied to
  substrates to provide a smooth-surface for
  subsequent coats.

  Urethanes: Materials based on resjns made by the
  condensation of organic isocyanates with com-
  pounds or resins containing hydroxyl groups.
  Categories of polyurethane coatings include: single
  . component prereacted-uretharie coatings; single
   component moisture-cured urethane coatings;
   single component heat-cured urethane coatings;
 two. component catalyst-urethane coatings; two .
 component polyurethane coatings; and one      ,
 component nonreactive lacquer-urethane solution
 coatings.                   ,

 Vacuum metallizing: Process in which surfaces
 are thinly coated by exposing them to metal vapor
 under a vacuum.

 Varnish: Clear or pigmented coatings formulated
 with various resins and designed to dry by chemi-
 cal reaction on exposure to air. These coatings are
 intended to provide a durable transparent or
 translucent solid protective film.

 Vehicle: The liquid portion of a coating in which
 the pigment is dispersed; it is composed of binder,
 solvent and diluent.

 Vinyl chloride polymers: Polymers formed by
' the polymerization of vinyl chloride or copolymer-
 ization of vinyl chloride with other unsaturated   .
 compounds, the vinyl chloride being in greatest
 amount by weight. Can be used in thermoplastic
 powder coatings.    •

 Vimyl resins: Resins which contain the unsatur-,
 ated vinyl group, (CH2=CH-) including polyvinyl
 acetate, polyvinyl chloride,:copolymers of these,
 the acrylic and methacrylic resins, the polystyrene
 resins, etc.                  ,•-.'.<

 Viscosity: The property of a fluid whereby it
 tends to resist relative motion within itself.  A thick
• liquid such as syrup has a high viscosity. Viscosity
  is often measured using an efflux type cup  which
  gives the time required for a given quantity of
  paint to flow through a hole in the bottom- of the
  metal cup at a given temperature (See Zahn Cup).

  Volatile organic compound (VOC): Any
  organic compound, not specifically exempted by
  the U.S. EPA, that participates in atmospheric
  photochemical reactions. VOCs may be emitted
  during the application and/or drying of coatings.
  In calculating the VOC content of the coating,
  exempt compounds and  water are excluded.
  Exempt compounds are  acetone, ethane, meth-
  ane, carbon monoxide, carbon dioxide, carbonic
  acid, metallic carbides, metallic carbonates,
  ammonium carbonate, methylene chloride, 1,1,1
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trichloroethane (methyl chloroform), 1,1,2
trichlorolotrifluproethane (CFC-113),
trichlorofluoromethane (CFC-11), dichlorodifluo-
romethane (CFC-12),- dichlorotetrafluoroethane
(CFC-1 HXchloropentafluoroethane (CFC-115),
trifluoromethane (CFC-23), and
chlorodifluoromethane (CFC-22). Although many
of these compounds are exempt under the VOC
rule, they may contribute to upper atmosphere
ozone destruction:

Volatility: The tendency of a liquid to evaporate.
Liquids with high boiling points have low volatility
and vice versa.

Voltage: measure of the potential difference
(•force or pressure) in electrical systems.

Waterborne coatings: Coatings in which water is
the major solvent or dispersant. Solvents or
dispersants include water soluble polymers (water
reducible), water soluble colloidal dispersions, and
emulsions (including latex).

Water-reducible coatings: see waterbome
coatings.

Weir: The (often adjustable) barrier that controls
the paint depth in an E-coat tank over which the
paint flows to the circulation pump, to be filtered,

We't-on-wet finishing: Applying a new coat over
an earlier applied coat which has been allowed to
flash-off but not cure.

Wrap around: Electrostatic effect where charged
coating particles curve around the part and are
deposited onto the rear side of the part.

Wrinkling: Distortion in a paint film appearing as
ripples.

Zahn cup: Commonly used efflux cup used for
measuring the viscosity of coatings. Other widely
used viscosity cups are the Fischer cup and the
Ford cup. These instruments measure the time
required for a given quantity of paint to flow  .
through a hole in the bottom'of a metal cup at a
given temperature.                          •
                                            156

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Appendix  G
Measuring   Transfer  Efficiency
Before conducting any transfer efficiency test,
several parameters need to be established:

+ What part will the test focus on?
* Which coatings and spray guns will the test
  use?                 ,
+ Who will apply the coatings?       •     ,
«• How will the test simulate day-to-day produc-
  tion conditions?

After identifying the basic parameters, the paint
operator mustestablish a fluid flow rate that is
representative of day-to-day production. The
operator needs to set the optimum air pressure for
coating atomization and to adjust the coating
viscosity and temperature to be representative of
typical operating conditions. If the operator is
using electrostatic equipment, they must confirm
that the parts are properly grounded, the coating is
 adjusted so that resistivity meets manufacturers
 recommendations, and the air velocity through the
 spray booth is neither too high nor too low. A
 decision also needs to be made in selecting the
 proper transfer efficiency test.

 Guidelines for Choosing Transfer
 Efficiency  Methods  !


 * If workpieces are small and lightweight (less
   than 70 pounds each), use the weight'(mass)
   method.

• * If workpieces are small and heavy (greater
   than 70 pounds each) with simple geometry,
   use the weight method by "wallpapering" with
   aluminum foil.                   '  .

  + If workpieces are small with complex geometry
   but the surface area can still be calculated, use
   the-volume method.                    .

  * If workpieces are small with a complex geom- .
   etry where the surface area cannot be calcu-
   lated, a special protocol may need to be
  - designed.  '
•* If workpieces are too large to fit onto a
  balance and have a simple geometry, use the
  weight method by "wallpapering" with alymi-  .
  num foil.
 V
* If workpieces are too large to fit onto a
  balance and have a complex geometry, but the
  surface area can still be calculated, use the
  volume method.

* If workpieces are large with a complex geom-
  etry where the surface area cannot'be calcu-
  lated,^ special protocol may need to be
  designed.

The Weight (Mass)  Method

Determining transfer efficiency on a weight or
mass basis, as is usually the case, requires pur-
chasing or renting an electronic balance capable of
measuring within 0.5 grams. There are balances
available that can weigh parts up to 70 pounds
(154 kilograms) with this accuracy. The balance
must sit on a hard surface, such as a metal table,
concrete floor, or cement slab. Operators should
never place a piece of cardboard under the
balance, as this will lead to inaccurate results.

In addition, the operator must shield the balance
from all drafts that occur on a factory floor (this
can be accomplished by surrounding the balance
with cardboard walls). The operator must also
 ensure that the pressure pot or coating reservoir is
 not-tod heavy for the balance and that the part to
 be coated falls within the acceptable limits of the
 balance.

 The balance should be set so that the air bubble in
 the bubble glass falls within the center of the glass.
 In addition, all four feet of the balance must be in
 firm contact with the ground or surface. Finally,
.the operator must calibrate the balance using
 standard weights, which are often supplied by.the
 balance manufacturer.
                                         157

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The paint operator should follow the steps below
to determine the weight of coating used during the
operation. This process begins by measuring the
liquid coating, then calculating the weight of the
solid coating.

1. Before beginning the test, appropriately label
each part and then accurately weigh the parts on
the balance. Record the weights.

2. Place the pressure pot or coating reservoir oh
the balance and slowly fill it with coating, ensuring
not to exceed the limit of the balance even after
tightening the pressure pot cover.

3. Before commencing the actual test, apply the
coating to several dummy parts to ensure that the
coating process is representative of actual operat-
ing conditions.

4. To begin the test, disconnect the fluid and air
hoses from the pressure pot. Do not allow any
paint to drip to the floor, as it is imperative that the
coating fills the line all the way up to the spray
gun. Record the coating weight and then replace
the air and fluid hoses and begin the spraying
operation.

5. For accurate results continue spraying until at
least one quart of paint has been used (approxi-
mately 2.2 pounds or 1 kg). After applying the
coating to the selected parts, immediately discon-
nect the fluid and air hoses from the pressure pot,
weigh the pot and record the second reading.
 Repeating this entire procedure three times will
 help determine an average transfer efficiency.

 At any time during the test, the operator should
 take a small grab sample (approximately one pint
 of the coating) from the pressure pot. The opera-
 tor should be sure to close the container to prevent
 solvent evaporation. The facility should send the
 sample to an analytical laboratory that will conduct
 a percent weight solids test in accordance with
 A STM D2369 (this is the standard test method For
 volatile coatings).

 The company should not bypass the sampling
 procedure by simply calling the coating manufac-
 turer to request information on the percent weight
 solids or referring to the MSDS. Even a small  .
 discrepancy between the manufacturer's value and
the actual value obtained from the pressure pot
sample will make a large difference in the transfer
efficiency calculations.

The weight of solids used is calculated by following
this equation:
                 Wt of Liquid Coating x % Wt. Solids
Wt of Solids Used = 	
                                 TOO
As noted earlier, before starting the transfer efficiency
test, each part must be labeled and weighed. After
applying the coating, the operator should allow
thorough curing before weighing the part again, If the
coating is normally air or force-dried, allow extra time
for all of the solvent to evaporate. Curing the parts in
an oven set at 230°F will result in a more accurate
transfer efficiency reading, even if this is not the
normal method for curing. This oven curing schedule
is identical to what a laboratory will use to determine
the percent weight solids of the one pint sample taken
earlier.

After the coating has thoroughly cured, the operator
should weigh the parts. The difference between the
weights of coated and uncoated parts represents the
weight of solid coating deposited. Knowing the weight
of solid coating used, and the weight of solid coating
deposited, the operator can calculate the transfer
efficiency as follows:
Transfer efficiency =
Mass of solid coa'ting deposited

    Mass of solid coa'ting used
 The credibility of the results depends entirely on the
 accuracy of the weighing. If the factory has drafts or
 vibrations that could affect the balance, the operator
 may wish to take two or three readings before record*
 ing any one weight. In addition, the laboratory deter-.
 mination of percent weight solids must be accurate.
 Finally, the accuracy of the results will increase if a
 number of parts are coated during any one test.

 When using this method for a large part with a
 .relatively simple geometry the operator can still use
 . the weight method by "wallpapering" the surface with
 pre-weighed aluminum foil. At the conclusion of the
 test, the operator should weigh the dried coating on
 the foil to complete the calculations.  ,
                                              158

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Costs .
The cost to conduct a transfer efficiency test can
be minimal. Companies can usually rent an
electronic balance for less than $300/week. A
laboratory charge might be $ 1507 sample. The
other "in-house" expense is labor., If a consultant
is retained costs might range from $3,000 to
$5,000, depending on the complexity of the
operation. '                   •

The  Volume  Method
The volume method is not as accurate as the
•weight method. To measure transfer efficiency
using the volume method, a laboratory must
determine the percent solids of the coating as
applied, as described in the weight method. To
determine the volume of solid coating deposited, a
lab measures the average film thickness of the
deposited coating; as well as the total surface area
of the coated parts.   •'
                                            159

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                      Reader Response Survey

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