f/EPA
United States
Environmental Protection
Agency
Enforcement And
Compliance Assurance
(2223A)
EPA 305-B-95-002
August 1998
Self-Audit And Inspection Guide
For Facilities Conducting
Cleaning, Preparation, And
Organic Coating Of Metal Parts
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Self-Audit & Inspection Guide
For Facilities Conducting Cleaning, Preparation,
and Organic Coating of Metal Parts
United States
Environmental Protection Agency
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DISCLAIMER
This publication has been prepared to provide general information on organic finishing operations and related
federal environmental issues only. State and local environmental regulatory information must be obtained from
appropriate state and local regulatory agencies. The information in this publication is not provided nor intended to
act as a substitute for legal or other professional services.
This Self-Audit and Inspection Guide was prepared by
Concurrent Technologies Corporation (CTC)
1450 Scalp Avenue, Johnstown, Pennsylvania 15904
in partial fulfillment of Contract DAAA21-93-C-0046
For sale by the U.S. Government Printing Office
Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328
ISBN 0-16-049750-7
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Foreword
Environmental auditors are charged with inspecting manufacturing facilities in a wide variety of
industries to ensure that the proper permits are on hand, record keeping is complete and accurate,
monitoring devices are in working order; and regulatory requirements are being followed. Although the
auditors may be well versed in statutes regarding pollutant releases to the air, water, and land, their
knowledge of facility technology may be limited. This is no surprise considering the wide array of
operations and equipment configurations typically found in one facility in order to produce a single
finished product. Likewise, facility engineers and workers are charged with maintaining facility
operations to ensure high productivity and quality workmanship. They are trained in the proper operation
of machinery, but may not be aware of environmental issues surrounding production. This, too, is
understandable in light of the many environmental regulations and policies. Individuals unfamiliar with
either the industry or the environmental requirements may find it difficult to associate the day-to-day
processes of a facility with a specific federal, state, or local environmental requirement. Recognition of
the need to bridge the gap between industry operations and environmental issues led to the creation of this
Self-Audit and Inspection Guide.
The Self-Audit and Inspection Guide project is sponsored by the United States Environmental
Protection Agency (EPA). The guide was developed by the National Defense Center for Environmental
Excellence (NDCEE). The Self-Audit and Inspection Guide consists of an audio-visual tool on a CD-
ROM and this accompanying written documentation. The multimedia tool utilizes video, photography,
animation, graphics, and text to communicate the relationship between technical and environmental
information within an industry. The audio-visual tool and written guide identify conventional process
steps, associated equipment, potential point source releases or waste generation activities, and federal
regulatory requirements only. State and local environmental regulatory requirements must be obtained
from appropriate state and local environmental agencies. This tool can be used in a classroom setting or
as a self-guided learning tool.
This Self-Audit and Inspection Guide is intended for individuals working in facilities conducting
organic finishing (painting) of metal parts. This tool will focus on the conventional and emerging
industrial processes that clean, prepare, and apply organic coatings to metal parts. The target audience
includes EPA and state inspectors responsible for inspecting conventional organic finishing process
activities. The guide will also benefit industry personnel who are responsible for compliance monitoring
and assurance in identifying links between the production process and environmental regulatory
requirements. The tool will provide an inside look at organic finishing lines so inspectors will recognize
the operations and production processes. The Self-Audit and Inspection Guide will assist internal and
external auditors in identifying activities and requirements necessary to complete an environmental audit
of production processes, equipment, and management systems.
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TABLE OF CONTENTS
Using the Self-Audit and Inspection Guide 1
Chapter One - Organic Finishing of Metals 1-1
Chapter Two - Coating Materials , 2-1
Section 1 - Solvent-Based Coatings 2-4
Section 2 - Waterborne Coatings 2-6
Section 3 - Powder Coatings , 2-7
Section 4 - Environmental Considerations for Coating Materials..... 2-9
Section 5 - Summary 2-14
Chapter Three - Surface Preparation 3-1
Section 1 - Chemical Coatings Removal 3-3
Section 2 - Mechanical Coatings Removal 3-6
Section 3 - Carbon Dioxide Blasting 3-9
Section 4 - Organic Solvent Cleaning 3-12
Section 5 - Aqueous Cleaning , 3-16
Section 6 - Drying 3-19
Section 7 - Environmental Considerations for Surface Preparation 3-20
Section 8 - Summary 3-26
Chapter Four - Application Methods 4-1
Section 1 - Spraying 4-3
Section 2 - Electrostatic Spraying 4-11
Section 3 - Electrocoating 4-17
Section 4 - Roll and Coil Coating 4-20
Section 5 - Dip, Flow, and Curtain Coating 4-24
Section 6 - Powder Coat Methods 4-28
Section 7 - Environmental Considerations for Application Methods 4-31
Section 8 - Summary 4-36
Chapter Five - Curing Methods............. 5-1
Section 1 - Convection Oven Curing 5-2
Section 2 - Infrared Radiation Curing 5-4
Section 3 - Environmental Considerations for Curing Methods 5-7
Section 4 - Summary 5-9
Chapter Six - Self-Audit Preparation Guide 6-1
Section 1 - Air Emissions 6-2
Section 2 - Wastewater Management 6-5
Section 3 - Hazardous Materials/Waste Management 6-9
Section 4 - Solid Waste Management 6-13
Section 5 - Community Right-to-Know 6-16
Section 6 - Pollution Prevention 6-19
Glossary
References
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USING THE SELF-AUDIT AND INSPECTION GUIDE
The Self-Audit and Inspection Guide consists of technical and environmental information that assists
personnel linking the two topics. The information is divided into categories representing the major
components or process stages that must be considered in the industry to create a final product. Within
each category are the conventional and emerging technologies used to complete a task. Using the guide
will provide external and internal auditors with the knowledge they need to properly perform an
environmental audit of a facility.
Technical and Environmental Information
The technical information includes a description of each individual technology. The equipment used in
each technology and the general operation of the process are described. The advantages and
disadvantages of the technology, such as restrictions on part configuration or efficiency limitations are
discussed as well.
The environmental information is divided into four categories: regulatory requirements, common causes
of violations, sources of pollution, and pollution prevention alternatives. The four categories are highly
dependent on one another, but each covers different issues that are valuable.
* The regulatory requirements section discusses Federal regulations specific to the industry and its
common pollutants. Statutes such as the Clean Air Act, Clean Water Act and Resource Conservation
and Recovery Act are covered.
* The section on common causes of violations presents areas in which a facility may be breaching the
regulatory requirements and will aid the facility in avoiding these problems.
4 The section on sources of pollution identifies pollutant releases to air, water, and land from various
operations in a typical facility.
* The pollution prevention alternative section covers changes to the technology or operating procedures
that would reduce or eliminate pollutant releases. Changes may include preventative maintenance,
material substitution, process or equipment alteration, production planning, recycling, or waste
treatment options.
CD-ROM and Written Guide
The Self-Audit and Inspection Guide includes a multimedia CD-ROM and this written documentation.
While the CD-ROM and written guide are intended to work together, each provides valuable information
and can be used independently of each other. The CD-ROM puts the user in a virtual factory where a
video of a technology in operation may be viewed. The user can navigate to whichever category of
operations and technology he chooses, quickly and easily. Technical and environmental information is
concise but illustrative. The written guide mirrors the CD-ROM in content, but provides more detail.
Each technology and its related environmental issues are covered in more depth. The guide provides a
general overview of the industry as a whole, as well as a description of each technical category. The
Self-Audit and Inspection Guide
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written guide also includes additional references on the industry, a glossary of industry terms, full part
and section titles from the Code of Federal Regulations (CFR), and additional sources for pollution
prevention opportunities.
A Guide for Organic Finishing Industries
This Self-Audit and Inspection Guide covers facilities conducting cleaning, preparation, and organic
finishing of metal parts. The first chapter provides an overview of an entire organic finishing facility and
the main components of producing a final product.
The next four chapters discuss the main components of an organic finishing facility and the technologies
of each. Chapter two covers coating materials including solvent-based materials, waterborne materials,
and powder coating materials. Chapter three discusses surface preparation technologies. First, coating
removal using chemical or mechanical methods is covered, followed by carbon dioxide blasting and
cleaning. Second, cleaning techniques using organic solvent or aqueous solutions are explained. Drying
is the final surface preparation step reviewed. Chapter four covers application methods for the different
coating materials and various part configurations. Both traditional and electrostatic spraying methods are
discussed. Other traditional application technologies included are dip, flow, and curtain coating methods
and roll or coil coating techniques. Newer technologies including elecrrocoating and powder coating
methods are also explained. The fifth chapter discusses the two major curing methods - conventional
oven curing and infrared curing systems. Chapters two through five also include the environmental
information specific to each category.
The final chapter presents an auditing preparation guide. The guide includes items to review or
investigate in preparation for an audit and is divided into the areas of air, water, solid waste, and
hazardous waste. References consulted for developing the Self-Audit and Inspection Guide as well as
those that provide developing information in the organic finishing field are provided at the end. Also
included in the written guide is a glossary of common terms from the organic finishing industry and
environmental subjects.
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CHAPTER ONE
ORGANIC FINISHING- OF METALS
This Self-Audit and Inspection Guide focuses on facilities conducting
organic finishing of metal products. Organic finishing, or painting,
involves the application of non-metal materials such as paint, clear films,
or varnishes. The resulting finish adds protection and/or decoration to
the workpiece during subsequent manufacturing steps or during use.
While some smaller facilities may perform only organic finishing of
metals, larger plants may include several additional manufacturing stages
related to producing a finished product. For example, an automotive
factory performs organic finishing, but also performs the prior steps of
metal stamping and forming, and final steps of assembling the painted
frame with the interior items.
In a typical organic finishing line, three major processes are performed.
First, surface preparation of the part removes old coating material, oils
and dirt. Second, the coating material is applied. Third, the coating
material is cured to create the final finish. Although not a "process" by
definition, the coating material also performs important functions in
order to create the final coating. Performance of the coating material in
the application and curing stages helps achieve the desired physical,
chemical, and aesthetic properties of the finish.
While a facility performing organic coating may have a production line
including each of the three processes, the specific type used at each stage
can vary widely. Several different methods have proven to be successful
for preparing surfaces, for applying coating materials, and for curing
coating films. The same is true for coating materials. Each brings its
own advantages and disadvantages to the production line. Because the
different stages are dependent on one another, they must be considered as
a system rather than as individual processes when designing the
manufacturing line or examining its environmental impacts.
Developing an organic finishing line is equivalent to solving a problem
with multiple variables. In addition to the relationships between the
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Chapter One Organic Finishing of Metals
three process steps and the coating material choice, the object being
coated must be considered. The substrate - the surface material to which
the coating will be applied, will impact the choice of technologies.
Aluminum substrates are sensitive to water, and may be adversely
affected by aqueous cleaning or waterborne paints. The part geometry
must also be considered. Curves, bends, corners, and recesses may be
challenging to coat with some techniques. A rounded part may not get a
uniform coat with a stationary spray system, while a small part may be
difficult to attach to an overhead trolley system. Finally, the end use and
the environmental conditions under which it will be used must be taken
into account. Harsh environments, such as those encountered by marine
vessels, may corrode coating films if not cured at the proper temperature.
The part description and choice of process technologies all contribute to
the engineering of an organic finishing system that will provide the
required coating characteristics. However, these items are not sufficient
determinants for designing and operating a facility. A facility must also
consider the environmental regulatory domain to ensure the system
complies with federal, state and local laws. Several parts of the Code of
Federal Regulations (CFR) cover operations of the metal finishing
industry and finishing processes specifically. The restrictions on harmful
air emissions, water releases, and solid waste disposal contribute to the
operating costs of a facility. Beyond regulatory compliance, facilities
must be proactive against waste generation and pollution and emphasize
increased efficiency in the use of raw materials and natural resources.
Identifying the sources of pollution and finding opportunities to prevent
pollution can greatly improve a facility's operations. Thus, all of these
technical and environmental issues should be considered when deciding
which type of coating material, surface preparation, application method,
and curing method is best for a particular facility.
The following chapters detail the individual operations of the organic
finishing industry. The guide includes chapters on four categories:
coating materials, surface preparation methods, application methods, and
curing methods. Each category represents the major components or
process stages that must be considered within an organic finishing
system. Within each category are the various technologies available.
Table 1-1 gives the various technologies discussed in each chapter. The
written guide provides a description of each technology, including the
equipment involved, operation of the process, and advantages and
disadvantages of the technology. With each technology is an overview
of specific regulations that apply, and unique sources of pollution and
pollution prevention opportunities that exist. Each chapter also provides
environmental issues for the process, regardless of the type of technology
used.
NOTES
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Chapter One Organic Finishing of Metals
Table 1-1: Organic Finishing Stages and Available Technologies
CATEGORIES
Coating
Materials
Surface
Preparation
Methods
Application
Methods
Curing
Methods
TECHNOLOGIES
Solvent-based - Traditional, High solids
Waterborne
Powder
Chemical Coatings Removal
Mechanical Coatings Removal
Carbon Dioxide Blasting
Organic Solvent Cleaning
Aqueous Cleaning
Drying
Spraying - Air-atomized, Airless, Air-assisted Airless,
High-volume Low-pressure
Electrostatic Spraying - Air-atomized, Airless, Air-assisted
Airless, Rotary bells & disks
Electrocoating
Roll and Coil
Dip, Flow, and Curtain
Powder Coat Methods - Electrostatic spraying, Fluidized
bed, Flocking, Flame spraying
Convection Oven
Infrared Radiation
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CHAPTER. TWO
COATING MATERIALS
Coating materials are applied in a thin film to provide protection or
decoration to a surface. Most films are thin in comparison to the
workpiece. In order to achieve the desired characteristics from the thin
film, the coating material formulation must be carefully considered in
relation to the part characteristics, surface preparation, application
technique and curing method. The correct combination of components
and process steps can lead to a film that provides long-lasting beauty and
defense against the elements.
Coatings can be formulated from a wide variety of chemicals and
materials or a combination of different chemicals. Each component in
the formulation serves a specific function. Four common components,
shown in Table 2-1, are pigments, additives, binders and the carrier fluid
or solvent.
Table 2-1: Common Components of Coating Materials
COMPONENT
Pigments
Binders
Additives
Carrier Fluid
CHEMISTRY
Insoluble solids
Polymers, Resins
Varies
Organic solvent,
water
FUNCTION
Commonly a colorant, used for
aesthetic quality
Adhesive between solids and surface,
create the coating film
Varies, can include stabilizers, curing
agents, flow agents
Liquid portion, means by which to
apply paint
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Chapter Two Coating Materials
* Pigments
Pigments are defined as any insoluble solid in coating materials.
Pigments are typically the colorant portion of a coating material, but can
also perform other functions. Some pigments provide corrosion
protection, stability in ultraviolet (UV) light, or protection from mold,
mildew or bacteria. Others can be used for their conductive ability,
texture, or metallic or pearlescent appearance.
• Binders
Binders primarily function as an adhesive to the substrate. Binders are
polymer resin systems with varying molecular weights. The molecules
in the binder crosslink during the curing stage to improve strength and
create the thin film. The type of binder usually gives the paint
formulation its name. Common binders are acrylics, epoxies, polyesters,
and urethanes. The viscosity of the paint is often attributed to the binders
contained in the coating formulation. Coating viscosity must be
considered when choosing certain application techniques.
• Additives
Additives are usually low molecular weight chemicals in coating
formulations that allow coatings to perform specific functions but do not
contribute to color. Non-pigment additives include stabilizers to block
attacks of ultraviolet light or heat, curing additives to speed up the
crosslinking reaction, co-solvents to increase viscosity, or plasticizers to
improve uniform coating.
* Carrier Fluid
The carrier fluid is typically a liquid such as an organic solvent or water.
The carrier fluid allows the coating material to flow and be applied by
methods such as spraying and dipping. This component may be in the
coating formulation before application, but evaporates afterwards to
allow the solid materials to immobilize and form the thin protective film.
Despite its temporary presence in the coating material, the solvent plays
a major role in how well the film will perform. Powder coatings have no
carrier fluid; they consist only of the other three components.
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Chapter Two Coating Materials
While the solids portion adheres to the workpiece, the solvent component
of coating materials evaporates and causes the most environmental
concern. The solvent materials are mostly volatile organic compounds
(VOCs) that may contribute to the creation of ozone (smog) in the lower
atmosphere and may be toxic to human health. Some solvents may also
be classified as hazardous air pollutants (HAPs). Federal environmental
statutes now regulate these VOCs and HAPs. One way organic finishing
facilities have responded to these regulations is by creating coatings with
lower solvent content.
Coating formulations vary widely, with different types and amounts of
pigments, binders, additives, and carrier fluids. The differences in
coating formulations provide film characteristics specifically set for the
part and its end-use. Often, one type of coating cannot be formulated to
provide all of the desired properties. Several layers of different coating
material may be applied to a surface to form a coating film that will
thoroughly protect the part. The first coat is typically called the primer,
or undercoat, and the final layers are called topcoats. Regardless of the
coating formulation or number of layers applied, proper part preparation,
application techniques, and curing processes are necessary for the desired
coating characteristics to be achieved.
Four common types of coating materials are solvent-based coatings,
high-solids coatings, waterborne coatings, and powder coatings. The
names are descriptive of the main type of carrier fluid present in the
coating. The chemical nature, coating characteristics and environmental
issues of these four coating materials are described in this chapter.
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Chapter Two Coating Materials
Section 1
Solvent-Based Coatings
Solvent-based coating materials have been the traditional coating used
for many years in all types of organic finishing industries, such as
automotive, aerospace, appliance, and furniture industries. In solvent-
based coatings, the final coating offers corrosion resistance, chemical
resistance, and is very durable.
* High-Solvent Coatings
Solvent-based coatings use organic solvents as the carrier fluid for the
pigments, binders and other additives. The organic solvent content of
coatings aids in the proper flow of the solids to adequately cover the
workpiece. The solvents usually evaporate once the part is cured and
dried, leaving behind a film to coalesce, crosslink, and adhere to the
substrate. Solvent-based coating materials are very versatile; they
provide good coverage and high quality coatings using a variety of
application methods.
Typically, solvent-based coatings are composed of 60% to 90% organic
solvents and 10% to 40% solids. The organic solvents used in high
solvent coating materials are typically low molecular weight
hydrocarbons or oxygenated compounds. The choice of solvent is based
on its ability to dissolve the other coating components and hold them in
solution, as well as its boiling point, evaporation rate, and flash point.
These properties determine operating parameters for the application and
curing stages. Other characteristics that are gaining importance are odor
and toxicity, which have an influence on worker health and
environmental safety.
For best results, parts to be coated with solvent-based coating materials
should be clean, oil free, and dry for best results. Solvent-based coatings
are typically applied using spray application methods, although liquid
flow techniques such as dip or curtain coating may be used. Curing and
drying takes place after coating applications to fully evaporate all solvent
materials.
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Chapter Two Coating Materials
The high-solvent, low-solids content of solvent-based coatings requires
the application of larger volumes of material to cover a given surface
area. Thus, when using solvent-based coatings, a high volume of organic
solvents is released. Because the organic solvents used in many solvent-
based coatings formulations are volatile organic compounds or hazardous
air pollutants, use of solvent-based coatings is being controlled by
environmental agencies. Some facilities using solvent-based coatings
may be required to use additional control equipment for application or
curing systems. Recovery of the evaporated solvents may be required
during application and curing stages to prevent volatile organic
compound emissions. While the solvent materials can be recovered and
reused, often they are incinerated to convert them back into water and
carbon dioxide while recovering the heat.
* High-Solids Coatings
An improvement in solvent-based coating formulations is high-solids
coatings. High-solids coatings are still solvent-based materials, but
contain a higher percentage of non-solvent material. Compared to the
10% to 40% solids content of regular solvent-based paints, high-solids
coatings contain 40% to 100% solids, and a smaller portion of the
formulation is organic solvents.
The higher solids content increases the viscosity of the material. To get
the lower viscosity required by many applications, solvents used in these
coatings are typically "strong" solvents, such as alcohol, esters, or
ketones. The strong solvents improve the dispersion of the concentrated
material and aid in the substrate wetting. If the coating material is still
too viscous, operation parameters must be adjusted. Heat can be applied,
pressure on the fluid can be increased, or components may be mixed just
prior to entering the spray gun.
A high-solids coating finish is similar to that of solvent-based coating
materials. Less material is needed, however, to cover the same amount
of surface area. As with other lower-solvent coatings, high-solids
coatings require proper surface preparation of the workpiece to ensure
proper adhesion of the coating. Clean up of high-solids coating materials
may be more difficult and require more solvents than solvent-based
coatings because of the larger percentage of solids.
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Chapter Two Coating Materials
Section 2
Waterborne Coatings
Waterborne coatings use water as the primary dispersal medium for the
pigments, binders, and other additives. However, waterborne coatings
still require some organic solvents to aid in proper flow and coalescence
of the paint film. The volume of organic solvents in waterborne paints
varies between 5% and 20%. Water makes up about 40% to 60% of
waterborne coating formulations. Solid materials make up the
remainder, 20% to 50%, about the same percentage as in solvent-based
coatings. When applied, the water and solvents evaporate, leaving the
pigment bound to the surface of the substrate material.
Waterborne coating materials can offer a finish that provides resistance
to corrosion, chemicals, weathering and fouling. Waterborne coatings
are available in a wide range of colors, although pastels are more
difficult to formulate. Waterborne coatings are used as primers or
undercoats for subsequent finishing processes, or as a decorative paint.
Newer formulations can be used for a variety of high performance
applications.
Parts should be cleaned prior to applying waterborne coatings to remove
oils and grease and other contaminants that repel the material, inhibit
uniform coating, and cause later coating failures. Common application
methods for waterborne coatings include spraying, electrostatic spraying,
electrocoating, roller or coil coating, and dip, flow, and curtain coating.
Drying and curing of the part is the final step.
One of the disadvantages of waterborne coatings is a shorter shelf life.
Due to the lower organic solvent content, stringent part cleanliness is
required, and the drying stage is longer and more controlled. In addition,
if exposed metal surfaces on application equipment corrode in the
presence of water, they may need to be replaced with stainless steel.
Switching to waterborne materials from solvent-based coatings,
typically, does not require extensive capital expenditures because similar
equipment is used to apply both. The lower organic solvent content is
one of the major advantages of waterborne coatings. The amount of
volatile organic compounds or hazardous air pollutants emitted form
waterborne coatings is much lower than with traditional solvent-based
coatings.
NOTES
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Chapter Two Coating Materials
Section 3
Powder Coatings
Powder coatings are close to 100% pigment and resin solids in dry form.
Powder coating materials are solid particles composed of pulverized
resins, pigment, modifiers, curing agents, and solid additives. Volatile
organics in powder coatings are found only in low concentrations, and
only as a result of the manufacturing process. Because of the minimal
organic solvent content, powder coatings are gaining popularity in many
industries.
Unlike solvent-based or waterborne coatings, powder coatings contain no
liquid diluent material to carry the solids. To form the final coating, the
solid particles are exposed to heat that melts the particles and allows
them to flow together and form a continuous film. When cooled, the thin
film hardens and protects the substrate. The resulting coating finish is a
high quality, durable, and corrosion resistant film.
Powder coating formulations require different types of resins than liquid
formulations to produce coating materials that are solid at storage
temperatures, yet capable of melting rapidly to low viscosity when
heated. Two basic types of powder coatings are thermosetting and
thermoplastic powders.
* Thermosetting Powder Coatings
Thermosetting powder coatings are based on polymers that chemically
change during the cure stage. When heated, the individual particles
crosslink to form bonds and become bigger polymer chains. When
cooled, the bonds remain to create the durable coating film. If the coated
part is later exposed to heat, the coating is unaffected. Thermosetting
resins include acrylics, epoxies, hybrids, polyesters, and urethanes.
* Thermoplastic Powder Coatings
Thermoplastic powder coatings are based on polymers that physically
change during the cure stage. When heated to the polymer melting
temperature, the particles flow together to coat the part surface. But the
individual particles do not undergo chemical change or form bonds.
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Chapter Two Coating Materials
When cooled, the film creates a shell that protects the part. If a coated
part is heated to the melting point temperature of the thermoplastic
resins, the coating will re-melt. While this is convenient for removing
the film, it can create problems if it occurs while the part is in use.
Common thermoplastic polymer types include polyethylene,
polypropylene, nylon, and polyvinyl chloride.
Prior to powder coating application, parts must be clean and dry. Powder
coating materials are very sensitive to the presence of surface
contaminants. Application methods include electrostatic spraying,
fluidized beds, or flame spraying. Parts can be preheated to help the
powder particles adhere to the surface during application. The coating
material must be heat cured to completely melt the particles and create
the final coating. With curing temperatures up to 450°F, melting
temperatures of the substrate must be considered; most metals can be
coated with powder coating materials with no problems. The main
advantage of powder coating materials is the absence of solvent materials
that create harmful air emissions.
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Chapter Two Coating Materials
Section 4
Environmental Considerations for Coating Materials
Many of the environmental issues that concern organic finishing
facilities focus on the impacts from the coating materials.. The coating
materials contribute significantly to all forms of pollution from a facility.
The components of coating materials evaporate to create air pollution,
contaminate water to form wastewater, and or contact other materials to
generate solid and hazardous wastes. This pollution is generated mostly
during the application and cleanup processes within a facility. This
section discusses the regulations that restrict use of; certain coating
materials, types of pollution that are formed, and pollution prevention
alternatives when using and handling coating materials.
Regulatory Requirements
Air Emissions
The Clean Air Act regulates the emission of volatile organic compounds
(VOCs) (40 CFR Part 60) and hazardous air pollutants (HAPs), (40 CFR
Part 61 and 40 CFR Part 63). Coating materials are the main source for
VOCs and HAPs from organic finishing operations. Evaporation of the
solvents during application and curing may produce sufficient VOC and
HAP emissions to subject an operator to major source requirements and
Title V permitting requirements. Specific standards of performance to
control emissions from various types of coating operations are found in
40 CFR 60 Standards of Performance for New Stationary Sources.
Standards cover the level VOC emissions from coating of metal
furniture, automobiles and light duty trucks, large appliances, coil
coating, and beverage can coating. VOC emissions are defined as the
mass of VOCs emitted per volume of solids applied. Operators should
refer to the specifications for their coating to determine if they fall within
the regulations.
Powder coating materials have very low or no solvent materials, so the
regulations for VOC or HAP emissions are less of a concern. In large
operations, VOC or HAP emissions may be released during the cure
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Chapter Two Coating Materials
Stage of powder coating materials. The small, dry powder coating
particles may fall under participate matter regulations in 40 CFR Part 50.
The particles can be suspended in exhaust air streams in amounts that
would subject an operator to Title V permitting requirements. Facilities
that utilize recovery systems avoid this problem.
* Wastewater
As part of the Clean Water Act, Effluent Guidelines and Standards for
Metal Finishing (40 CFR Part 433) have been established that limit
concentrations of heavy metals and toxic organics in wastewater streams.
Coating materials often contain components classified as toxic organics,
and some may include metals. These materials can enter the liquid waste
streams through the use of waterwash spray booths, when cleaning
coatings from containers or equipment, or following accidental spills.
Actual limits for effluent constituents depend on the size of the operation
and the amount of wastewater generated from the facility. If the facility
discharges directly to receiving waters, these limits will be established
through the facility's National Pollutant Discharge Elimination System
(NPDES) permit (40 CFR Part 122). Facilities which are indirect
dischargers releasing to a publicly owned treatment work (POTW) must
meet limits in the POTW's discharge agreement. Wastewater streams
with concentrations exceeding permit limits will require pretreatment
prior to discharge to receiving waters or to a publicly owned treatment
works. Pretreatment may include separation of liquid wastes to remove
solvents and settling or precipitation of solid materials.
• Solid and Hazardous Wastes
Under the Resource Conservation and Recovery Act (RCRA), organic
finishing facilities are required to manage listed and characteristic
hazardous wastes (40 CFR Part 261). Coating materials may contain
constituents, such as solvents, listed or characterized as hazardous
wastes. Residual coating materials, their containers, and contaminated
materials (including rags, masking material, coveralls, filters, and other
process materials) may require treatment as hazardous waste depending
on their formulation. Hazardous waste management (40 CFR Part 262)
includes obtaining permits for the facility in order to generate wastes,
meeting accumulation limits for waste storage areas, and manifesting
waste containers for off-site disposal. Responsibilities will vary
according to the amount of hazardous waste material generated; facilities
generating at least 100 kilograms of hazardous waste per month must
comply with the hazardous waste generator requirements of 40 CFR Part
262.
Each state and/or region is primarily responsible for the regulation of
non-hazardous solid wastes (those not governed by the hazardous waste
NOTES
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Chapter Two Coating Materials
provisions of RCRA). Check with state environmental agencies for
specific information or guidance.
4 Community Right-to-Know
The Emergency Planning and Community Right-to-Know Act (EPCRA)
requires facilities to notify employees, customers and the surrounding
community of certain hazardous chemicals and materials (40 CFR Parts
355 and 370) that are present on-site. Coating materials that contain
solvents purchased and stored in sufficient quantities may subject a
facility to several EPCRA requirements. Facilities may be required to
inform the local emergency planning committee (LEPC) and the state
emergency response commission (SERC) of the materials stored on site,
to devise emergency response plans for reacting to spills, and to notify
authorities of accidental spills and releases (40 CFR Parts 302 and 355).
Coating materials stored on-site may also require facilities to submit
Material Safety Data Sheets (MSDS) for these materials to state,
regional, and local organizations, while disposed volumes of the material
may have to be documented on annual Toxic Release Inventory reports
(40 CFR Part 372).
Common Causes of Violations
Violations can occur when coating materials are not used properly.
Facilities may be using a coating formulation with a high VOC content
that exceeds the limits for their type of industry. The VOC and HAP
content may be allowed to evaporate and accumulate above limits
allowed by Clean Air Act Title V permits. Coating materials can
contaminate liquid waste streams also. This contamination may be
accidental, such as spilt material mixing with wastewater, or intentional,
such as with the use of water wash spray booths or during cleaning
activities. Contaminated water streams may contain pollutants in
concentrations that exceed the limits established by facility NPDES
permits or POTW discharge agreements. In such cases, effluent may not
be directly released to water systems or to publicly owned treatment
works without pretreatment.
Coating materials remaining on rags, filters, masking papers, and coating
containers may be considered hazardous waste. If hazardous, the waste
must be properly stored, manifested and disposed according to RCRA
standards (40 CFR Part 262). Coating materials may contain substances
defined as hazardous chemicals or extremely hazardous substances.
Depending on the quantity of material on-site, facilities must have an
MSDS for each formulation, maintain records for TRI reporting, and
cooperate with local emergency planning committees.
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Chapter Two Coating Materials
Sources of Pollution
The components of coating materials that create pollution include the
organic solvents. These evaporate to create air pollution in the form of
volatile organic compounds or hazardous air pollutants. The components
can also contaminate water streams or solid materials that would require
additional treatment. Cleaning up coating materials may also require the
use of solvents, adding to the overall pollution. Another source of
pollution is with the coating material as a whole. Coatings may expire or
become contaminated with dirt or other coatings and no longer meet
quality standards, thus becoming waste. In addition, coatings that are not
used completely in a job and have no use in another job may be
considered waste as well. The containers for coating materials, unless
they can be returned and refilled by the manufacturer, are waste, too.
Pollution Prevention Opportunities
Pollution prevention in an organic finishing facility starts with the
coating materials. Substituting high-solids, waterborne, or powder
coating materials for solvent-based coatings can greatly reduce the
harmful air emissions from a facility. Compared to traditional solvent-
based coatings, other high-solids, waterborne and powder coatings
contain much lower amounts of volatile organic compounds. In addition,
these materials have higher solids contents which results in a lower
volume of material needed for a given surface area. If substitutions
cannot be made, other actions can reduce the impact from the solvents.
• Materials and Waste Handling and Storage
Material handling procedures are another focus. Enclose or cover
containers of coating material when not in use to minimize the release of
solvent vapors and lower the possibility of contamination from facility
dust and dirt. Restrict traffic in storage areas to reduce spills and
accidents. Keep storage and work areas clean so that spills and leaks are
more noticeable and reaction time to clean up is reduced. Control the
temperature in storage areas to prevent the freezing and heating of
coating materials that will spoil them. Segregate non-hazardous coating
solids from hazardous solvents and thinners, and label containers to
prevent mixing. Separation of the materials reduces the amount of
hazardous waste that is produced. Coating material solids can be dried
and treated as a solid waste, thus allowing for disposal in a landfill.
* Operations and Procedures
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Chapter Two Coating Materials
Proper scheduling and procurement can reduce the amount of residual
coating material waste. To reduce residual coatings, buy only as much
material as needed to complete the job. Mix remaining light colored
coatings into darker colored coatings where possible. Purchase coating
materials in the largest containers possible for the volume; since the
surface area to volume ratio of the container is lower, less material is left
on the inside of the containers to be thrown away. Work with coating
vendors to have larger containers returned for refilling. Rotate stock of
coatings to use older material first (first in - first out practice). Before
discarding expired coatings, test to see if they would still meet quality
requirements. Donate or sell old and unwanted coating materials as raw
material to others or see if the vendor will take it back.
* Training
Finally, train employees on safe handling of coating materials and wastes
and encourage continuous improvement. Training familiarizes workers
with their responsibilities, which reduces spills and accidents.
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Chapter Two Coating Materials
Section 5
Chapter Summary
Coating materials provide the protective finish for numerous
manufactured items. Various formulations are available to meet the
needs of almost any requirement, from corrosion protection to aesthetic
coloring. The main types of coating materials are solvent-based, high-
solids, waterborne, and powder. The general composition of these four
coating material types is shown in Figure 2-1. Formulations fall into the
categories based on the main carrier fluid of the material.
100
90
80
70
60
50
40
30
20
10
0
Solvent-based
Paints
—| Organic
-I Solvents
High Solids
Paints
SH Water
Waterborne
Paints
Powder
Coats
Solids-Pigment
& Binder
Figure 2-1: Percentage Composition of Coating Materials
Beside the physical and chemical characteristics of the final coating film,
organic finishing facilities must consider the environmental impact
presented by the various coating materials. The volatile organic
compounds and hazardous air pollutants emitted from the coating
material creates air pollution. Solvent-based coating materials have
much higher levels of these pollutants than waterborne and powder
coatings. Additional measures and precautions must be taken within
organic finishing facilities when using high-solvent coatings. Equipment
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Chapter Two Coating Materials
used for applying the coatings must be modified to minimize or capture
emissions. Special care is required for handling, storing, and disposing
the coating materials. In addition, facilities must protect workers from
exposure.
Facilities may reduce the level of air pollutants in two ways. Using less
paint during the application stage so that fewer pollutants are released, as
discussed in Chapter 4 on application methods. The other way is to use,
where possible, coating materials with lower, or no, harmful solvents.
Many facilities have opted for the latter, making waterborne and powder
coatings common in manufacturing.
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CHAPTER THREE
SURFACE PREPARATION
Proper preparation of the part surface prior to organic finishing is
essential to the performance of the final coating. Improper treatment of
the part surface can lead to poor adhesion of the coating material, surface
defects, and aesthetic problems. The choice of surface preparation
technology used will depend on the part substrate, size and shape, as well
as its previous manufacturing steps. Surface preparation includes
stripping of previous coatings, removal of contaminants such as grease
and oils, and drying. More than one process may be necessary to fully
prepare a workpiece for a new organic finish. Regardless, almost all
parts will go through a surface preparation step prior to coating.
Old coating material should be completely removed before refinishing.
Applying a new coating over previous coatings can hamper its
performance, especially if the old coating is flaking or peeling. The new
coating will not adhere to the actual part surface but to the old layer of
finish and will flake or peel away from the part. Removal of old coatings
also provides a flat, even surface so that the new coating will have a
uniform thickness. Other coatings or surface damage, such as weld
burns, should also be removed. Coatings removal can be completed in
several ways, using chemical or mechanical means to prepare the part
surface.
Other preparation steps include those where the surface is cleaned and
the substrate is activated. Using solvents and water to separate the
unwanted materials from the substrate, cleaning removes grease,
fingerprints, dirt, and other contaminants that will interfere with the
application and curing of the finish. Chemical activation steps promote a
chemical reaction on the surface of some metals so that it more readily
accepts the coating material. Activation is completed by applying a
water-based solution of active ions to the part. These surface preparation
techniques are often performed in series with the parts moving from a
wash step immediately to a rinse step and then to an activation step.
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Chapter Three Surface Preparation
Drying is often required as a last step, and then the parts move directly to
the application process.
Environmental impacts must also be considered when choosing surface
preparation methods. The harsh chemicals and cleaners used to remove
contaminants can create a large volume of waste liquids. The residual
grease, dirt, and coatings must also be disposed. Some of these cleaners
and residual material may be classified as hazardous material, adding to
the burden on the facility.
Six surface preparation techniques are described in this chapter:
* Chemical coatings removal,
* Mechanical coatings removal,
* Carbon dioxide blasting,
* Organic solvent cleaning,
* Aqueous cleaning, and
* Drying.
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Chapter Three Surface Preparation
Section 1
Chemical Coatings Removal
Removal of the old coating on metal parts is essential prior to applying a
new coat. Old coatings may not provide a receptive surface and,
therefore, would prevent the new coat from adhering. Chemical removal
of organic coatings involves breaking bonds between substrates and
coating layers. The chemicals soak into the coating and soften or
dissolve it. The solutions are designed to effect only the coating material
and not the surface of the substrate. A number of chemical agents exist
which are able to break the bond between an organic coating and the
substrate to which it has been applied. Three traditional methods of
removing organic coatings are hot caustic stripping, cold chemical
stripping, and molten salt baths.
4 Hot Caustic Stripping
Hot caustic stripping uses alkaline solutions at high concentrations and
temperatures to dissolve coating bonds. Chemicals such as sodium
hydroxide or chlorinated solvents are used to create the coatings removal
solutions. Some coating materials with low initial solvent content show
resistance to hot caustic solutions and must be stripped by other methods.
* Cold Chemical Stripping
Cold chemical stripping uses organic solvents such as methylene
chloride (MEC), methyl ethyl ketone (MEK), or phenol compounds to
remove coating from parts. This method can be used with many
different metals and organic coating types, including lower solvent
coating formulations.
Hot and cold chemical strippers are typically applied in immersion tanks.
Heat, if used, is provided by steam coils. The parts are dipped into the
tank that may be agitated. After the coating has been loosened by the
chemical solution, parts are rinsed to remove excess stripping solution
and coatings. Rinse water tanks are used if the coating will flake off, but
pressurized spray rinsing is recommended if the coating will fall off in
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Chapter Three Surface Preparation
sheets or large pieces. Stripping solutions must be cleaned regularly to
remove accumulated solids and extend the effectiveness of the bath;
overflow screening or filtration can be used to remove coating materials.
Figure 3-1: Chemical Coatings Removal.
• Molten Salt Stripping
Molten salt stripping baths are operated at temperatures between 550°
and 900° F and parts are dipped in the solution for a few minutes. The
salt solution converts the organic portion of the coating to carbon dioxide
and water allowing the inorganic components such as pigments to slough
off. Parts must be rinsed to remove excess salt particles which results in
an alkaline wastewater stream.
Molten salt stripping is not energy intensive. While the bath must heat
the part, the chemical reaction of the coating change creates heat that is
absorbed by the bath. Another advantage is that the bath keeps working
when coating materials are high, requiring only small additions of
chemicals. The inorganic by-products accumulate in the bath, saturate it,
and then as more are introduced, they precipitate. The precipitated
sludge is easily removed from the bottom of the tank. Sludge might
contain some metals that may be characterized as hazardous waste.
Part complexity is not a primary issue in the effectiveness of chemical
removal methods. Solutions can easily penetrate small crevices and
around bends. Chemical solutions may not remove all coatings,
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Chapter Three Surface Preparation
therefore, they are typically used in conjunction with mechanical
coatings removal.
Chemical coatings removal may be considered a pollution prevention
alternative since it aids in the proper application of coating materials
thereby reducing rework or reject parts. However, other concerns make
it less acceptable than other coatings removal methods. Environmental
impacts from chemical coating removal systems stem from the large
volume of chemical solutions used. The chemical baths must be replaced
to maintain effective stripping, resulting in liquid waste disposal
problems. Some chemicals may be classified as hazardous, adding to the
burden. Rinse waters used after chemical coatings removal and residual
coatings must also be treated and disposed properly. In addition, the
solutions may pose health concerns for workers.
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Chapter Three Surface Preparation
Section 2
Mechanical Coatings Removal
Removal of old coating is essential prior to applying a new coat. Old
coatings may not provide a proper surface and would prevent the new
coat from adhering to the part. Mechanical removal of coatings is
accomplished by methods that mechanically abrade or embrittle the
coating. Mechanical removal methods separate the coating from the
substrate without chemically altering the composition of the coating.
Three types of mechanical coatings removal are dry-abrasive blasting,
wet-abrasive blasting, and waterjet blasting.
* Dry-Abrasive Blasting
Dry-abrasive blasting physically removes coating material from a
substrate using a stream of solid particles propelled at high velocity
against the coated surface. On contact with the part, the dry media
dislodges the coating and it flakes off. Dry blasting media include
inexpensive materials such as sand, steel, glass beads, agricultural media
(e.g., wheat starch, crushed nutshells, fruit pits), manufactured sponge,
and plastic beads. This makes it a good option to consider for large-area,
high-throughput stripping projects. The rate of coating removal is fair to
good, depending on the blast media selected. In general, hard abrasive
media strip coatings faster than soft media does.
Waste from dry abrasive processes consists of coating chips mixed with
abrasive media. Most media can be easily separated from the coating
debris, using gravity separation in air or water. Steel, plastic, glass, and
sponge media may be recycled and reused. However, dry-abrasive
blasting generates excessive noise and dust, which makes it undesirable
for use in areas where other manufacturing or maintenance activities are
occurring.
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Chapter Three Surface Preparation
Figure 3-2: Dry-Abrasive Blasting.
4 Wet-Abrasive Blasting
In wet-abrasive blasting, a stream of low- to medium-pressure (up to
15,000 pounds per square inch (psi)), water containing abrasives,
typically sand or sodium bicarbonate, is directed at a coated surface.
Solvents, such as alcohols or aliphatic hydrocarbons, may be
incorporated into the liquid stream to facilitate coating removal. Wet-
abrasive processes remove organic coatings at a moderately fast rate and,
thus, may be suitable for large-area stripping projects. An advantage of
wet-abrasive blasting over dry-abrasive blasting is that less dust is
created. Two major disadvantages of wet-abrasive blasting are
wastewater from the process may need to be collected and treated, and
the abrasive media is not reusable.
* Waterjet Blasting
Waterjet blasting uses the force of water at very high pressure (greater
than 15,000 psi) without the addition of abrasives or solvents to remove
organic coatings. Waterjet systems use less thrust and, therefore, result
in less operator fatigue and better stripping performance than other
manually operated blasting systems. Water that is contaminated with
coatings particles is generated from waterjet operations. The water can
be filtered and reused, leaving only the coating residue and filters to be
disposed. Rust inhibitors may need to be applied to water-sensitive
substrates during or after liquid blasting to reduce flash corrosion.
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Chapter Three Surface Preparation
Figure 3-3: Wet Abrasive Blasting System.
Part complexity plays a role in the effectiveness of mechanical removal
methods. Blasting techniques are line-of-sight methods so the blast
stream may miss some areas on a complex part. Also, blast media used
in abrasive blasting may get lodged into recesses and small crevices of a
part and require further handling, such as blowing with compressed air,
to ensure complete removal. Because of these difficulties, mechanical
coatings removal is typically used in conjunction with chemical coatings
removal methods. The combination of the two methods helps to remove
all coating residue and blast media from the part surface.
Mechanical coatings removal may be considered a pollution prevention
alternative since it aids in the proper application of coating materials
thereby reducing rework or reject parts. However, other concerns make
it less acceptable than other coatings removal methods. Mechanical
coatings removal methods have some environmental impacts. For large
facilities, a large volume of waste material (dry or wet) may be
generated. If the blast media or coating material contain hazardous
materials such as solvents or heavy metals, the residual waste may be
considered hazardous. Separation and reuse of the blast media will help
reduce this. Mechanical coatings removal operations are regulated by 40
CFR Part 63 Subpart GG - National Emission Standards for Aerospace
Manufacturing and Rework Facilities. This regulation requires that
facilities provide sufficient airflow and air filtration to prevent air
particulates from accumulating.
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Chapter Three Surface Preparation
Section 3
Solid carbon dioxide (CC^) or "dry ice" blasting processes may be used
to remove organic coating materials and particulates by an impact-
flushing method. With carbon dioxide blasting, solid CO2 particles are
propelled at the part to dissolve organics and dislodge coating materials.
Unlike other mechanical coating removal methods, carbon dioxide
blasting systems remove coating materials when the particles hit and
bounce back off the surface of the part. The removal action of carbon
dioxide systems is depicted in Figure 3-4. Particulate and molecular
coating materials are first knocked lose by the impact of the pellet.
Then, as the CC>2 pellet undergoes phase transformation from a solid to a
vapor (sublimation), the coating materials are carried away from the part.
The contaminant matter falls to the ground and may be collected while
the CC>2 is free to escape into the atmosphere.
Two types of carbon dioxide blasting, which use either frozen CC>2
pellets or CC>2 snow, are currently available. Carbon dioxide pellet
blasting involves projecting small beads of solid COa at high velocities
toward the part that is being cleaned. Either a centrifuge or compressed
air is used to project the pellets. A centrifuge minimizes pellet
degradation by throwing the pellets rather than forcing them along with
compressed air. Centrifuges also make contaminant collection less
complicated by stirring up less dust. Carbon dioxide snow blasting uses
smaller blast particles and utilizes spray systems. Carbon dioxide snow
is formed when liquid CC>2 is allowed to expand rapidly through a
nozzle. These snowflakes are then carried by a high velocity stream of
pressurized CO2 gas. Carbon dioxide snow is less abrasive then pellets
but cleans as effectively.
Carbon dioxide blasting systems are operated at pressures typically
between 50 and 300 pounds per square inch (psi). Some systems that
operate at pressures below 150 psi are portable which adds to their
versatility. Because the CO2 gas is non-toxic and cleanup is minimal, the
system can be used to perform in-line cleaning without dismantling
machinery or interrupting production. Another benefit of carbon dioxide
blasting is that drying is not necessary.
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Chapter Three Surface Preparation
The carbon dioxide pellet is
accelerated toward the coated
substrate.
The carbon dioxide pellet
penetrates the coating to loosen
it from the substrate.
The carbon dioxide pellet
sublimates on impact with the
substrate turning into carbon
dioxide gas.
The "mini-explosion" of the
carbon dioxide changing to gas
further tears the coating away
from the substrate.
The coating material falls to the
ground while the carbon
dioxide gas is released to the
atmosphere.
Figure 3-4: Carbon Dioxide Blasting Action.
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Chapter Three Surface Preparation
Figure 3-5: Carbon Dioxide Blasting System.
As with any line-of-site process, carbon dioxide blasting is not applicable
to some parts with complicated geometries because the projectiles are
unable to reach into tight or hidden spaces. The method is not
aggressively abrasive so cleaning times may be longer than with other
methods. However, other benefits of this coating removal method make
this a viable alternative. For instance, carbon dioxide blasting does not
alter or damage surfaces of the workpiece. Because the solid CC>2 turns
to gas, no abrasive media is entrapped in crevices and both the snow and
pellet methods add no excess solids or liquids to the waste. Also, solid
CC>2 blasting may be used on parts that are sensitive to water.
Carbon dioxide blasting is a good 'alternative to other coatings removal
and cleaning methods due to the low environmental impacts. No
additional liquid, solid, or hazardous waste beside the coating residual is
created since the carbon dioxide turns to gas and is released to the
atmosphere. One worker safety issue with carbon dioxide blasting must
be addressed, however. Carbon dioxide gas is denser than air and may
accumulate in work areas. Without proper ventilation, oxygen levels
may fall and pose problems for workers.
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Chapter Three Surface Preparation
Section 4
Organic Solvent Cleaning
Organic solvent cleaning applies an organic chemical to a part to remove
organic coating materials such as grease or dirt. Applied in liquid form,
the solvents dissolve the coating materials to separate them from the
substrate. Organic solvents do not usually chemically affect the surface
of metal substrates, which makes these solvents useful on a wide variety
of materials. Some solvents evaporate after application, leaving no
liquid waste. Others are effective for many cleaning cycles, which
reduces the need to change cleaners often. In addition, some coating
materials are easily separated from organic solvents by settling or
skimming, further extending the effectiveness of the solvent.
Traditional organic solvents, provided in Table 3-1, include
fluorinated compounds, such as chlorofluorocarbons (CFCs) and
hydrochlorofluorocarbons (HCFCs). These materials have been used
extensively because of their effective cleaning nature, low flash point,
and low toxicity to humans. However, they have been targeted as ozone
depleting substances and are not as widely accepted as in the past.
Aliphatic hydrocarbons consist of naphtha, mineral spirits,
kerosenes, and straight chain hydrocarbons. Chlorinated solvents, such
as trichloroethylene, perchloroethylene, and methylene chloride, are also
widely used. These materials effectively clean a variety of contaminants,
especially heavy grease, tar, waxes, and soils. They, too, have been
targeted for phase-out by environmental regulations due to their toxicity.
Alcohols, ethers, ketones, and esters also work well as organic
solvent cleaning agents. Alcohols (such as ethanol and isopropanol) and
several glycol ethers are effective solvents, but are highly flammable.
These organic solvents are typically used only in small-scale cleaning
processes. Esters have good solvent properties, but some dibasic esters
have such low vapor pressures that a residual film is left on a surface
after application.
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Chapter Three Surface Preparation
Table 3-1: Common Organic Solvent Cleaners.
SOLVENT GROUP
Fluorinated solvents
Aliphatic solvents
Chlorinated solvents
Alcohols
Ketones
Ester solvents
Aromatic solvents
EXAMPLES
chlorofluorocarbons, hydrochlorofluorocarbons
hexanes, mineral spirits
methylene chloride, trichloroethylene, perchloroethylene
isopropanol, methanol, ethanol, isobutanol
acetone, methyl ethyl ketone, methyl isobutyl ketone
ethyl acetate, isopropyl acetate, glycol ether acetate
toluene, xylene
Organic cleaning solutions may be applied to a part by immersion,
spraying, hand wiping, or vapor systems.
• Immersion
For immersion, parts are dipped and soaked in a bath of solvent. The
cleaning effectiveness of the solvent may be augmented by the addition
of heat or by agitation of the bath fluid. Agitation is done by mechanical
means or through ultrasonic bombardment. Immersion baths need to be
changed or filtered to maintain appropriate levels of cleaning
performance. Parts must be dried after immersion to remove excess
solvent. Immersion is adaptable to a variety of part geometries and sizes
but may not be as fast as other cleaning technologies.
4 Spraying
Spray cleaning is performed by spraying the part with a low-foaming
organic solvent cleaner. Low-pressure nozzles are arranged to spray the
part from many angles. Spray washing provides a high level of
cleanliness, is inexpensive, and offers a high throughput rate. However,
it is a line-of-site process making it difficult to clean complex parts
thoroughly.
4 Hand Wiping
Hand wiping involves the manual application of the cleaner to an area
and then wiping with a rag or brush. This process is not applicable to
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Chapter Three Surface Preparation
large-scale cleaning or to solvents that pose a health risk. However, it is
typically used to clean small areas, or for touch-up work.
* Vapor Systems
In vapor degreasing processes, organic vapors are condensed onto dirty
parts in an enclosed chamber. After parts have been in the vapor system
for a set time, the chamber or part is heated to vaporize the solvents and
"dry" off the parts. Vapor degreasing can be done under vacuum
conditions or with a cooling zone above the vapor area to prevent loss of
solvent vapors. Part complexity is a concern in vapor degreasing
applications because undercut and bottom surfaces will not be coated
with vapors. Part orientation is essential to maximize the upward surface
areas and achieve proper cleaning.
Figure 3-6: Vapor Degreasing System.
The effectiveness of the organic solvent solution can be reduced by
minimizing the contamination level of the fluid and reducing the fluid
evaporation rate. Coating materials that build up in the solution must be
removed regularly for the solution to retain its cleaning capability.
Because organic solvents have high evaporation rates at room
temperatures, care must be taken to cover solvent cleaning systems to
avoid unnecessary loss of solution. Organic solvents are also highly
flammable and may require explosion prevention equipment.
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Chapter Three Surface Preparation
Organic solvents have been targeted for reduction due to the
environmental impacts they impose. The solvents evaporate to form
volatile organic compounds and hazardous air pollutants. Worker health
is also a concern. Environmental regulations have been written which
impact solvent cleaning systems. 40 CFR Part 63 Subpart T - National
Emission Standards for Halogenated Solvent Cleaning applies to all
batch vapor, in-line vapor, in-line cold, and batch cold solvent cleaning
operations using methylene chloride, perchloroethylene,
trichloroethylene, 1,1,1-trichloroethane, carbon tetrachloride, or
chloroform. The regulation requires proper design of cleaning systems
to minimize evaporation and release of the solvent vapors. Other
industry-based regulations put restrictions on organic solvent cleaning
systems (40 CFR Part 63 Subpart GG). Facilities can prevent some
impacts by proper use of the solvent materials. This includes careful
handling of materials, analytical testing to determine solvent
effectiveness, and segregation from non-hazardous materials.
Some organic solvents can be combined with water to help reduce their
negative environmental effects, while maintaining their cleaning
capability. Semi-aqueous cleaners degrease metal parts with an organic
solvent wash and a water rinse, or with an emulsion of the organic
solvent and water. Organic solvents used in semi-aqueous cleaners
include aliphatic hydrocarbons and terpenes. These cleaners have a
neutral to slightly alkaline pH and are less corrosive toward reactive
metals, such as beryllium, than strong alkaline aqueous cleaners.
Although using semi-aqueous cleaners reduces environmental concerns,
the cleaners still produce vapor emissions that may be toxic or odorous.
In addition, semi-aqueous cleaning systems produce and increase volume
of wastewater that must be treated to remove the organic solvents.
Safety concerns, such as flammability, must still be considered when
choosing this alternative.
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Section 5
Aqueous Cleaning
Aqueous cleaning processes use solutions which consist of water and a
small concentration of chemical cleaning agent to remove coating
materials by chemical dissolution or emulsification. Additional washing
and rinse stages can be included as needed to achieve proper surface
preparation. Water is an effective solvent for ionic and other water-
soluble coating materials. Hard water or process water may leave a film
or deposit on the substrate; therefore, water softening or the use of
deionized water may be necessary. Aqueous cleaning solutions may also
include additives such as surfactants, saponifiers, and anti-foaming
agents to enhance cleaning. Depending on the additive, aqueous cleaners
can be neutral, alkaline, or acidic.
The most commonly used aqueous cleaners are alkaline cleaners. Most
alkaline solutions have a pH of 10 to 12. They are used to remove flux,
emulsify oils, break apart fats and solid soils, neutralize fatty acids, and
precipitate hard water ions.
Acidic cleaning solutions have a pH of less than 7. They are used to
remove oil, grease, shop soils, drawing compounds, light rust and scale,
or to etch metal surfaces for better adhesion in subsequent processes. A
common type of acid cleaning is phosphating in which iron, zinc or
magnesium ions in a water solution are applied to a part. The phosphate
pretreatment improves the paint bond and prevents the spread of
corrosion under the coating. Acidic cleaners require a preliminary
alkaline rinse to effectively remove heavy deposits of oil or grease.
Typical aqueous cleaning systems include several stages: washing with
an aqueous solution, rinsing with clean water, and drying. Aqueous
cleaning is performed in several ways. Aqueous cleaning solution can be
sprayed onto parts via nozzle manifolds. The spray manifolds facilitate
the cleaning process by showering the solution directly on to the surface
of the parts. The cleaning capability is further enhanced by fixturing the
parts in such a way that exposes their maximum area to the cleaning
solution. Aqueous cleaning is also performed in immersion tanks that
are equipped with mechanical or ultrasonic agitation capability. A water
rinse is typically required as a final step to remove any residual cleaning
NOTES
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Chapter Three Surface Preparation
solution. Complete removal of coating materials and the cleaning
solution is necessary to allow proper adhesion of coatings materials.
Drying is then performed to remove excess water from the part.
Acidic Phosphate
Washl Drain Rinse Drain j Drain Rinse
i i it ii it
^VENTILATION FAN
fl .BAFFLE rACCESS DOOR
VERTICAK
PUMPS
Hg !b
r — ;?== —
i *
3JL^
.^
ti it
Z DOUBLE REMOVABLE u DRAIN PAN
SCREENS
Drain Rinse Drain
Mi
P
Xlb
• jW irr-
V i
:NTILATION
^•OVERFLOW
TROUGH
Figure 3-7: Aqueous Cleaning System with Wash, Rinse, and Dry Stages.
The wide range of available aqueous cleaners makes it possible to find a
cleaner for virtually any substrate, as long as the substrate is not
adversely affected by water. The type of aqueous cleaner to be used is
determined by the substrate and the contaminant, as well as part size and
geometry. In order to achieve acceptable cleanliness levels with aqueous
solutions, the cleaning system must be optimized according to
temperature, agitation, concentration, and time. Proper adjustment of the
four variables will ensure that all coating materials are sufficiently
removed.
To extend the life of aqueous cleaning solutions, coating materials
should be removed from the solutions at regular intervals. Many
cleaners hold soils in suspension while agitated. After the solution cools
or sits for a period of time, the contaminant materials will separate from
the solutions in the holding tank. Oils float to the surface and can be
skimmed off while particles fall to the bottom as sludge. The cleaning
solution can then be pumped out arid reused. This type of separation can
be done in a holding tank or during a daily shutdown of the cleaning
system. If gravity separation alone does not provide sufficient
contaminant removal, filtration may be necessary. Typically, operators
face a trade-off between how well the aqueous cleaner removes oils and
dirt from the part and how well coating materials can be separated from
the cleaner.
Compared to cleaning with organic solvents, aqueous cleaning may
require longer wash cycles and more space for equipment. The process
also requires that parts be rinsed thoroughly, which may be difficult to do
with complex parts. Care must be taken to reduce flash rusting of water
NOTES
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Chapter Three Surface Preparation
sensitive substrates. But aqueous systems do not create as many
environmental concerns for facilities. Aqueous cleaning methods
provide a relatively safe cleaning system because solutions have low
toxicity and are typically nonflammable. The large volume of water used
can usually be treated to remove dirt and grease, cleaning solutions, or
other coating materials, allowing the water to be reused in subsequent
cleaning operations. Aqueous cleaning systems are sited under some
industry-based air regulations (40 CFR Part 63 Subpart GG) which place
limits on the percentage of water in the solution.
NOTES
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Chapter Three Surface Preparation
Section €
Drying is the final step in many surface preparation operations for
organic finishing. Drying removes any residual liquid remaining after
organic solvent or aqueous cleaning. Parts must be free from cleaning
solutions and water prior to paint application to ensure that the coating
properly adheres to the surface.
Drying typically occurs in convection ovens, although radiation systems
can also be used. The heat generated in an oven accelerates the
evaporation of liquid cleaning solutions or rinse solutions from the part.
Conventional dry-off ovens consist of a large metal, brick, or ceramic
housing structure where the heat is circulated. The heat can be generated
by electricity, gas, or other energy sources. Ovens can be of a batch type
where parts remain stationary inside and are put in and removed at
various times. They can also be continuous systems where parts move
through the heated area on a conveyor or overhead trolley. Some dryers
are a continuation of the washer system, rather than a separate unit.
Dry-off ovens are similar in theory to ovens used after coating
application for curing and drying. The heated air is circulated through
the oven shell to evaporate the residual liquid. Parts are usually
contained in the ovens for three to five minutes. Dry-off oven
temperatures are usually operated around 100° to 200° F. Temperatures
and times will vary with the size of the part and if the dry-off stage is
used for a preheating step as well. Because the temperature of the part
may affect some application methods and coating materials, the part
temperature is monitored during the drying stage.
If an aqueous cleaning system is used, the oven removes rinse water; for
solvent cleaning systems, excess cleaning solution is removed. Care
must be taken when drying parts after solvent cleaning to prevent the
temperature from reaching the flash point of the solvent to avoid
combustion. Exhaust systems may have to capture solvent vapors prior
to release to the atmosphere as well.
Drying systems have very low environmental impacts. Gas-powered
ovens may create additional nitrous oxides (NOX) emissions for a facility.
Otherwise, ovens are a major source of energy consumption.
NOTES
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Chapter Three Surface Preparation
Section 7
Environmental Considerations for
Surface Preparation
Surface preparation methods create large volumes of waste material,
consisting of old coatings, dirt and other coating materials, blast media,
solvents or liquid solutions. Only the last preparation step, drying, poses
few environmental burdens for facilities. This section discusses the
regulatory requirements, common causes of violations, sources of
pollution, and pollution prevention opportunities for surface preparation
methods.
Regulatory Requirements
• Air Emissions
Except for the standards for halogenated solvent cleaning discussed in
section 4, few regulations specifically address surface preparation
methods. Facilities must be aware of the overall emission of volatile
organic compounds (VOCs), hazardous air pollutants (HAPs) and
particulates from their operations, however. The VOC and HAP
emissions may be formed from chemicals, solvents, or other additives to
Stripping and cleaning solutions. Particulates may accumulate during dry
media or carbon dioxide blasting. Release of these pollutants are
governed by 40 CFR Part 60, 40 CFR Part 61, 40 CFR Part 63, and 40
CFR Part 50. Facilities may produce sufficient levels of emissions to
subject them to major source requirements and Title V permitting
requirements.
* Wastewater
Wastewater issues are also a concern for organic finishing facilities. As
part of the Clean Water Act, Effluent Guidelines and Standards for Metal
Finishing (40 CFR Part 433) have been established that limit
concentrations of heavy metals, toxic organics, and conventional
pollutants in Wastewater streams. Several components of surface
preparation operations are classified as water pollutants including
NOTES
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Chapter Three Surface Preparation
chemical stripping solutions, caustic solutions, wet-abrasive blasting
residue, organic solvent solutions, or aqueous cleaning solutions. Also,
the residual coating solids or sludge in the solutions may contain metals.
These materials can enter the wastewater through liquid dripping off of
parts, through rinse activities, when cleaning equipment, and from
accidental spills or leaks in equipment. Actual limits for effluent
constituents are dependent on the size of the operation and the amount of
wastewater generated from the facility. If the facility discharges directly
to receiving waters, these limits will.be established through the facility's
National Pollutant Discharge Elimination System (NPDES) permit (40
CFR Part 122). Facilities which are indirect dischargers releasing to a
publicly owned treatment works (POTW) must meet limits in the
POTW's discharge agreement. Wastewater streams with concentrations
exceeding permit limits will require pretreatment prior to discharge to
receiving waters or to a publicly owned treatment works. Pretreatment
may include separation of liquid wastes to remove solvents, and settling
or precipitation of solid materials.
* Solid and Hazardous Wastes
Under the Resource Conservation and Recovery Act (RCRA), organic
finishing facilities are required to manage listed and characteristic
hazardous wastes (40 CFR Part 261). Several materials from surface
preparation methods may classify as hazardous materials including
chemical stripping solutions or organic solvent cleaners. Sludge from
these operations and even dry coatings residual may also qualify and will
add to the overall volume of waste generated. Hazardous waste
management (40 CFR Part 262) includes obtaining permits for the
facility in order to generate wastes, meeting accumulation limits for
waste storage areas, and manifesting waste containers for off-site
disposal. Responsibilities will vary according to the amount of
hazardous waste generated; facilities generating at least 100 kilograms of
hazardous waste per month must comply with the hazardous waste
generator requirements at 40 CFR Part 262.
4 Community Right-to-Know
The Emergency Planning and Community Right-to-Know Act (EPCRA)
requires facilities to notify employees, customers and the surrounding
community of certain hazardous chemicals and materials that are present
on-site. Large organic finishing facilities may use hazardous materials in
sufficient quantities to subject a facility to several EPCRA requirements.
Facilities may be required to inform the local emergency planning
committee (LEPC) and the state emergency response commission
(SERC) of the materials stored and used on-site, devise emergency
response plans for reacting to spills, and notify authorities of accidental
NOTES
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Chapter Three Surface Preparation
spills and releases (40 CFR Parts 302, 355, and 370). The materials used
in chemical coatings removal solutions may also require facilities to
submit Material Safety Data Sheets (MSDS) for these materials to state,
regional, and local organizations, while disposed volumes of the material
may have to be documented on annual Toxic Release Inventory reports
(40 CFR Part 372).
+ Material Substitution
Although not directly regulated by the EPA, mechanical coatings
removal and carbon dioxide blasting technologies generate a high level
of noise. Equipment used to compress and pump materials, the exhaust
of the blast stream, and the media striking the substrate create sufficient
decibel levels to require process engineering controls and hearing
protection.
Common Causes of Violations
Common causes of violation of regulatory requirements occur typically
on a facility level. Most regulations cover the facility as whole, rather
'than individual processes. Facilities must be aware of the total
generation of pollution from all sources in order to obtain sufficient
permitting or treatment processes. Facilities must also maintain all
monitoring, recordkeeping, and reporting documents as required.
Emission of volatile organic compounds or hazardous air pollutants from
chemical solutions or accumulation of particulates may occur and exceed
limits established in a Clean Air Act Title V permit. Blast media,
coating material, and substrate residue form dust in the blast area. Some
particles may be small enough to qualify as respirable particulates
capable of penetrating lung tissue. Typical hazards include exposure to
silica and lead.
Wastewater may exceed permit limits for solvents, solids, oils or other
contaminants. Excess concentrations can occur during normal
operations, when cleaning systems or work areas, or through accidental
spills of material. If the effluent exceeds the limits established by facility
NPDES or POTW permits it may not be directly released to water
systems or to publicly owned treatment works without pretreatment.
Facilities must assure that all hazardous materials are handled properly.
The materials must be labeled, stored, and disposed according to
regulations. Materials should be tested to determine if they qualify as
listed or characteristic hazardous wastes. Items such as sludge from strip
tanks, coating residual, or used liquid solutions may qualify based on
additional contaminants in the material. In addition, the facility must be
NOTES
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Chapter Three Surface Preparation
aware of the total quantity oa the site. Total volumes are considered for
emergency planning and notification regulations. MSDS for all
chemicals should be available for employees and the public.
Sources of Pollution
Surface preparation methods generate a large portion of the waste from
organic finishing facilities. Air pollutants may be generated from the
coatings removal and cleaning solutions that have organic solvents.
Particulates can accumulate when stripped from a part. Facilities may
take measures to capture these pollutants by including ventilation
systems with filtration and chemical recovery or incineration. The large
volume of liquid materials used in chemical coatings removal, wet-
blasting, organic and aqueous cleaning systems adds a significant amount
of waste to facilities. These materials must be replaced regularly and old
solution treated or disposed properly. Residual coating materials and
other contaminants also add to the amount of waste generated by a
facility. Even if the materials can be separated from the stripping or
cleaning solution, the materials must be disposed, and may qualify as
hazardous materials.
Pollution Prevention Alternatives
Facilities can reduce the pollution from surface preparation methods in
numerous ways. If possible, processes can be exchanged for those that
create less waste. Chemical coating removal may be replaced with a
mechanical coating removal method, organic solvent cleaning replaced
with an aqueous system. Carbon dioxide blasting, with the lowest
impacts, may be able to replace both removal and cleaning steps.
Perform all operations in designated areas and enclose them if possible.
This will contain wastes to smaller area and prevent contamination of
parts or facilities. If this is not an option, steps can be taken to improve
the current process and reduce pollution.
• Material Substitution
Facilities can reduce pollution by switching to materials that are less
polluting. Chemical coatings removal solutions are available that do not
contain organic solvents and that are less harmful to workers. Aqueous
solutions have been proven to be as effective for organic solvent
cleaners. Substituting semi-aqueous solutions or organic solvents with
lower vapor pressures can also help reduce risk. Carbon dioxide blasting
uses gas that is not harmful.
NOTES
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Chapter Three Surface Preparation
• Material and Waste Handling and Storage
Even if harmful chemicals are still required for adequate surface
preparation, proper handling and storage can reduce pollution and
hazards. Restrict traffic in chemical storage areas to reduce spills and
accidents. Keep storage and work areas clean so that spills and leaks are
more noticeable and reaction time is reduced. Enclose or cover
containers of chemical coatings removal and cleaning solutions when not
in use to minimize the release of solvent vapors and lower contamination
from facility dust and dirt. Segregate non-hazardous wastewater and
other materials from hazardous liquids and organic solvents, and label
containers to prevent mixing. Separation of the materials reduces the
amount of hazardous waste that is produced. For non-hazardous
materials, recycle if possible by removing residual coatings from blast
media. Recycle water from wet-abrasive blasting to other processes such
as rinse baths, facility cleanup, or other uses where a small concentration
of coating materials will not matter.
* Operations and Procedures
Minor changes to current operations and procedures can also reduce
waste generation. Pre-inspect parts prior to processing. Optimize
processes to perform properly with minimal solution additions, with
lower concentrations, and shorter processing times. Proper adjustment of
operating parameters, such as time, agitation, solution concentration,
blast pressure, and temperature, will improve surface preparation without
requiring stronger solvents or longer processing times. Modify part
arrangement to ensure that all surfaces are reached. Use counter-current
systems for liquid solutions, especially rinse cycles. Backflow the
cleaner water from the final rinse stage to the tanks for previous rinses
and finally into the stripping or cleaning solution itself. Remove coating
materials from the solutions regularly so that effectiveness of the solution
is maintained and lasts longer. Separate coating residue, dirt, oils, and
other contaminants using filtration, gravity separation, or membrane
technologies (crossflow filtration). Reducing heat and stopping agitation
will promote separation of coating materials in batch systems.
• Maintenance and Housekeeping
One of the most important steps for pollution prevention is a regular
interval of maintenance and housekeeping. Check equipment regularly
for leaks, broken valves, incorrectly operating monitoring devices, etc.
This will ensure that processes are running at optimal settings. Regular
cleaning of equipment and surface preparation areas quickly identifies
problem areas and creates a safer work environment. Minimize
accumulation of soils, dirt, and oils by practicing good housekeeping.
NOTES
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Chapter Three Surface Preparation
Keep the facility clean and use proper part handling procedures to reduce
part contamination initially
4 Training
Finally, train employees to operate processes properly and to fully
understand their responsibilities in the workplace. Train employees on
safe handling of materials and wastes and encourage continuous
improvement. Training familiarizes workers with their responsibilities,
which reduces spills and accidents.
NOTES
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Chapter Three Surface Preparation
Section 8
Chapter Summary
Surface preparation is essential to good organic finishing results.
Surface preparation removes old coating materials, dirt, oil, or other
contaminants leaving a clean, even surface for the new coating material.
Performing proper surface preparation techniques also reduces pollution
in the long run by ensuring that parts have good coating characteristics,
eliminating the need to rework parts and waste more materials, time, and
energy. Summarized in Table 3-2 is the six surface preparation methods
discussed in this chapter. Each provides sufficient cleaning of a
workpiece prior to coating material application. Virtually any
contaminant can be treated and removed from various substrates to
ensure good coating characteristics.
The environmental impacts of each surface preparation method must be
considered with their use. While all provide adequate preparation of the
substrate, the amount of waste generated varies widely. Large volumes
of waste material and liquids may be generated with any one system.
With careful operation and procedures, these impacts can be reduced or
contained to minimize waste and risk.
Table 3-2: Summary of Surface Preparation Methods.
SURFACE
PREPARATION
METHOD...
Chemical Coatings Removal
Mechanical Coatings
Removal
Carbon Dioxide Blasting
Organic Solvent Cleaning
Aqueous Cleaning
Drying
REMOVES...
Old coatings
Old coatings,
surface dirt
Old coatings,
dirt, grease
Dirt, grease
Dirt, grease,
rust, scale
Excess solvents,
water
WHILE CREATING...
Air emissions, hazardous
waste, wastewater
Dust, wastewater, solid
waste
No harmful by-products
Air emissions, hazardous
wastes, wastewater
Wastewater, sludge
Heat, air emissions
NOTES
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CHAPTER FOUR
APPLICATION METHODS
Coating application is the second process in organic finishing systems.
The coating materials are applied to the workpiece in a variety of ways.
Coatings materials can be sprayed over the part, or the part can be dipped
into a tank of coating material. Other methods include showering parts
with coatings or rolling parts between large barrels to spread on the
coating. Transfer of coating materials can be enhanced with the use of
electrical potential between the coating and the part.
Several variables dictate the choice of application method. Part
geometry, appearance of the coating finish, and production rate all
influence the type of application method. A part with recesses and
rounded areas that requires a high-gloss finish will be coated by a
different system than a flat sheet which needs a protective primer
coating. Facility constraints will also determine the choice of application
method. The configuration of the application equipment is dependent on
space or climate. Systems can be manually or automatically controlled.
Other systems may require extra equipment, such as holding tanks or
outside air supply to operate properly.
Similar application systems may operate at widely varying parameters.
The viscosity of the coating material, the desired thickness of the final
coating, and the complexity of the part will determine the best operating
parameters for the application method. Thus, part temperatures, dip
times, number of coats, or the amount of current used will be different.
These operating parameters are carefully monitored by plant engineers to
ensure the quality of the coating meets specifications.
One factor that is important to all application methods is the transfer
efficiency of coating material onto the part. Transfer efficiency is the
percentage of solid coating material used that actually deposit on the
surface of the part. The higher the transfer efficiency, the better, as more
coating material adheres to the part and less is wasted. Transfer
NOTES
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Chapter Four Application Methods
efficiency ranges from 25% to 40% for conventional spray systems to
almost 100% for dip and powder coating methods. Much of the
pollution and waste created from organic finishing operations can be
minimized or eliminated by improving the transfer efficiency of the
application system. If the transfer efficiency cannot be improved,
pollution control technology and waste handling measures must be
employed.
The environmental issues associated with organic finishing application
methods mostly stem from the type of coating material used. More
issues arise with the use of solvent-borne coatings than with waterborne
or powder coating materials. However, the application processes create
pollution and waste that can cause violations but that can be prevented.
This chapter discusses six common application technologies for organic
finishing:
* Spraying,
* Electrostatic Spraying,
4 Electrocoating,
* Roll and Coil Coating,
* Dip, Flow, and Curtain Coating, and
* Powder Coating.
Each section provides a description of the technology and any specific
environmental considerations. The final section discusses the regulatory
requirements, common causes of violation, sources of pollution, and
pollution prevention alternatives for the application methods.
NOTES
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Chapter Four Application Methods
Section 1
Spraying
Spray application is the most common technology for applying organic
coatings to metals. With spraying, coating materials are forced through a
small orifice with or without mixing with air. The change in pressure,
and any mixing with air, causes the liquid paint to be atomized into small
particles. Additional jets of compressed air can be used to shape the
collection of particles and move them in the right direction. When the
small droplets contact the workpiece, they flow together to form a film
that covers the material. The method is relatively quick, simple, and
provides good coating characteristics.
The main equipment in spray applications includes a spray gun, air
supply system, fluid supply system and connectors. Spray guns control
the volume and direction of the fluid and any air streams. The fluid and
air streams are released when the trigger on the gun is squeezed.
Different nozzles can be attached to the guns to change the exit area and
thus the spray pattern. The air supply system consists of a combination
of air compressors, filters, heaters and supply hoses. The fluid supply
system can vary widely in complexity. A canister of coating material
can be attached to the spray gun with gravity forcing the material through
the gun. Other systems have mixing containers at remote locations and
use pumps and hoses to carry the fluid to the gun. Spray systems can be
operated manually or run by automated robots.
Four types of spray systems commonly found in metal finishing
operations include air-atomized spraying, airless spraying, air-assisted
airless spraying and high-volume, low-pressure spraying. Each provides
good coverage of simple to complex parts rather quickly. The main
difference between the technologies is in the use of compressed air to
promote atomization of the liquid coating.
* Air-Atomized Spraying
Conventional air-atomized spraying is the most widely used technique to
apply industrial coatings. Both coating materials and compressed air are
NOTES
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Chapter Four Application Methods
fed to the spray gun. The fluid and air mix when they exit the gun
forming a fog of very small coating particles. Additional jets of air are
directed into the atomized stream to form smaller droplets and an
elliptical or fan spray pattern. Conventional systems use air pressured
around 60 pounds per square inch (psi).
Conventional spray painting is very versatile. It can spray coating
materials with high viscosity and allows substantial control over the
spray pattern. Patterns ranging from a large spray to a fine dot can be
obtained by using the controls on the gun to alter air and paint flow. The
main disadvantage of air-atomized spraying is the low transfer
efficiency. Usually, less than half of the paint discharged from the gun
actually reaches the surface to be painted.
Air Supply
Pressure
Tank
Figure 4-1: Air-Atomized Spraying System.
* Airless Spraying
Airless spray systems offer some improvements over air-atomized
systems. Airless systems do not directly use compressed air to create the
mist of paint. Instead, hydraulic pressure atomizes the paint by pumping
it at high pressures (between 500-4500 psi) through a small orifice at the
spray nozzle tip. As the fluid is released to the air, the change in
pressure separates it into small droplets forming a finely atomized spray.
The high discharge velocity reduces the particle size and propels the
minute particles to the work surface.
Airless spraying requires careful operation to achieve a good coating.
Air is not used to guide the spray, therefore, the operator has less control
over the spray pattern. In addition, paint exits the nozzle at a high rate of
speed. If the spray movement is paused over the surface, a build up of
paint will occur resulting in runs or sags. Also, the coating particle size
in airless spraying systems is coarser than that of air-atomized systems,
so an even finish may be difficult to achieve. However, airless systems
NOTES
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Chapter Four Application Methods
apply paint at a faster rate than traditional systems, so the same area can
be covered in a shorter time. Airless systems are typically used for broad
surface areas such as ship hulls or rail cars. Transfer efficiencies of
airless systems are approximately 20% to 50%.
Air Supply
Figure 4-2: Airless Spraying System.
+ Air-Assisted Airless Spraying
Another spray coating technology is air-assisted airless spraying which
combines the mechanics of airless and air-atomized spray techniques.
Like an airless system, the fluid stream is partially atomized by forcing
the liquid stream at a high pressure (between 200-800 psi) through a
small fluid nozzle tip. Complete atomization is achieved from
compressed air jets from the face and horns around the nozzle, as done in
air-atomized systems.
This method provides the finely atomized spray pattern seen with airless
systems but results in a finer finish like traditional spray methods. The
spray pattern is easier to control because the fluid stream exits the gun at
a slower rate and because air-jets help guide the atomized particles.
Transfer efficiency is improved to around 30% to 60 %.
* High-Volume, Low-Pressure Spraying
High-volume, low-pressure (HVLP) spraying techniques are a more
efficient application method than the other spray methods. Like air-
atomized systems, compressed air is mixed with the liquid paint in the
spray gun creating the spray and moving it toward the workpiece. Some
HVLP systems use standard compressed air, which has its pressure
restricted in the gun. Other HVLP systems use an externally fed turbine
NOTES
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Chapter Four Application Methods
to create the high-volume, low-pressure air. The air is often heated
which helps reduce the viscosity of some paints. HVLP systems operate
at air pressures around 10 psi. Some systems are portable which adds to
their versatility.
Air Supply
Fluid
Siphon
Figure 4-3: Air-Assisted Airless Spraying System.
High-volume,
Low-pressure
Mr Supply
Pressure Tank
Fluid
Figure 4-4: High-Volume, Low-Pressure Spraying System.
NOTES
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Chapter Four Application Methods
HVLP systems produce a soft spray that penetrates recesses and cavities
of complex workpieces. The resulting spray is not as fine as air-
atomized systems, however, so the final coat may not be as smooth.
Extra equipment to create the proper airflow is required and an adequate
supply of clean, dry air must be available in the facility. The transfer
efficiency of HVLP spraying reaches 65% to 75%.
In many cases, spray painting occurs in enclosures to help confine the
paint material that does not deposit on the workpiece. Spray booths have
equipment designed to control airflow. An exhaust system pulls paint-
laden air through a filtration device that captures excess atomized
particles. Additional equipment may be required to control the release of
emissions from the organic solvents in the coating material. Spray
booths can allow movement of parts by conveyor or trolley if necessary.
Two types of spray booths use dry filters or waterwashes.
4 Dry Filter Spray Booths
Dry filter booths are most common. These booths have cloth or polymer
mesh filters to capture coating materials in the exhaust air. Often, a
series of progressively tighter filters are used to remove larger, then
smaller atomized particles. Filters must be replaced when clogged with
coatings, and may be classified as a hazardous waste depending on the
type of coating material used.
* Waterwash Spray Booths
In a waterwash booth, the rear of the enclosure has a curtain of water or
water sprayed from nozzles. As the exhaust system draws air through
the water, coating particles are trapped in the water while clean air exits.
The water and coatings fall to the bottom of the booth and are collected.
Some coating materials can be separated from the water allowing both to
be recycled and reused.
Spraying methods can be used to apply most liquid coatings including
solvent-based, high-solids or waterborne materials. Consideration must
be given to the viscosity of the coating material and the operating
parameters of the spray system when determining if a certain material
can be. used. Viscosity can be reduced by adding solvents or water to
NOTES
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Chapter Four Application Methods
thin the coating material, or by adding heat. Heat gives a more
consistent flow and faster curing, but reduces the freshness quality or
"pot life" of the paint. Pot life refers to the time from when a container
of paint is first opened to the time the paint expires, or looses important
coating characteristics.
Spray methods cover large areas very quickly and coat complex parts
easily. However, transfer efficiency is typically low compared to other
coating methods because much of the atomized coating material does not
reach the surface to be painted. In general, as atomization increases, the
size of the paint particle decreases. The smaller particles are less
influenced by their velocity from the gun and are more likely to miss the
target, as shown in the following figure. Some atomized particles are
blown away by surrounding air currents or simply fall to the ground due
to gravity before reaching the part. This is called fallout. Some coating
particles will rebound off the part rather than adhering. The biggest
waste in coating materials is usually due to overspray. Overspray is the
coating material that misses the part at the edges.
Rebound
Overspray
Substrate
Fallout
Figure 4-5: Waste Coating Materials from Spray Application Techniques.
Operator technique of manual spray application technologies is critical to
proper coating. The operator controls the distance from the gun to the
surface, speed of each stroke, pattern overlap, spray gun angle, and
NOTES
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Chapter Four Application Methods
timing of triggering. All of these parameters contribute to successful
application of the coating materials and how much coating material is
wasted. Automated systems with fixed guns mounted on reciprocators or
guns mounted on movable robots alleviate some of the inconsistency in
applying coatings with spray technologies.
Cleaning spray equipment is relatively simple. Compressed air, water or
solvents replace the coating material in the fluid supply and the spray
gun is triggered. The air, water or solvents flush the unused paint
through the system, clearing all fluid supply lines and the gun. Air and
water flushes help reduce the amount of solvents required, but are often
followed by solvent flushes to completely clean the systems. Cleaning
must be done thoroughly to ensure no paint remains and clogs any lines.
Additional hand cleaning of the gun may require dismantling of the gun
components, such as the nozzle tip.
Figure 4-6: Spraying Application.
Facilities utilizing spray application systems must consider several
environmental issues. Spray systems atomize the solvents contained in
the coating material, which increases their evaporation. This increased
evaporation rate creates more air pollution burdens than other application
methods. Spray systems are specifically regulated under 40 CFR Part 63
Subpart GG - National Emission Standards for Aerospace Manufacturing
and Rework Facilities. Aerospace facilities may use application methods
or equipment that have demonstrated reduced HAP and VOC emissions
that achieve emissions reductions equivalent to HVLP or electrostatic
spraying methods.
NOTES
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Chapter Four Application Methods
The major source of pollution from spraying applications is wasted
coating material due to poor transfer efficiency. For most spray systems,
only about half of the coating material used actually ends up on the
workplace. A significant amount of coating material is wasted during
these processes. Since the coating material then falls on filters, masking
materials, clothing or elsewhere, additional waste is created when these
items are disposed or cleaned.
Pollution prevention can be achieved from spray systems by taking
measures to improve the transfer efficiency of the system. Equipment
changes from air-atomized spray systems to airless, air-assisted airless,
or high-volume low-pressure spray systems, which have less
atomization, improve transfer efficiency of coating materials. Adding
electrostatics to the spray system can also improve transfer efficiency by
increasing the attraction between coating particles and the work piece.
Proper operation of the equipment can also improve transfer efficiency
and reduce waste. Reducing the pressure of compressed air leaving the
gun reduces the forward velocity of the particles so they are less likely to
rebound off the part. Lower air pressure also reduces energy demand for
the compression system. Adjusting the air current velocity in spray
areas, especially with automated spray systems where worker safety is
not an issue, will prevent atomized coating particles from straying from
the workpiece. Spacing parts closer together on conveyors also helps
eliminate overspray coating particles. Most importantly, training
operators to manipulate spray equipment properly can provide much
improvement. Spray gun movement must be compatible with the fluid
spray rate. The spray gun should be held about twelve inches from the
part and perpendicular to the work piece surface. The spray pattern
should be adjusted to be slightly smaller than the part profile. The spray
gun should be triggered at the correct time on leading and trailing edges.
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Chapter Four Application Methods
Section 2
Electrostatic Spraying
Electrostatic spraying improves on traditional spray technology by
adding electrical forces to improve deposition of coating materials on the
workpiece. An electrode imparts a negative charge on the coating
material. The negatively charged particle is now pulled toward the
workpiece by electrostatic forces as well as directed toward it from the
velocity of the spray. As the coating droplet deposits on the part, the
charge dissipates.
High Voltage Cable
Conveyor
Electrostatic
Power Supply
...
Potential
Figure 4-7: Electrostatic Spraying System.
Electrostatic spraying can be completed with methods similar to
traditional spray technologies. Like traditional spray technologies,
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Chapter Four Application Methods
electrostatic spraying systems combine fluid and air streams to create a
mist of atomized coating particles. But electrostatic systems also
incorporate a power supply to create the different charges between the
coating material and workpiece. Common electrostatic spray systems
include air-atomized spraying, airless spraying, air-assisted airless
spraying, and bell or disk rotary spraying systems.
* Air-Atomized Electrostatic Spraying
Air-atomized electrostatic systems mix fluid and compressed air streams
at the gun tip to atomize the coating materials into a fine spray. An
electrode located at the gun tip imparts an electrical charge to the spray
particles on exiting the gun. Additional air jets may be used to further
define and control the spray pattern. Transfer efficiency is between 40%
and 80%.
4 Airless Electrostatic Spraying
Airless electrostatic systems force fluids at very high pressures through a
very small orifice at the gun tip. When the fluid is exposed to the air, the
coating material becomes atomized and charged by an electrode. The
size and shape of the spray pattern is controlled by the orifice size.
Airless systems apply paint at a very fast rate, so operator control is
essential for a smooth, uniform finish. Transfer efficiency can range
between 40% to 70%.
«• Air-Assisted Airless Electrostatic Spraying
Air-assisted airless systems can also be used with electrostatics. These
systems utilize the principles of airless systems by forcing the fluid at
high pressure through a small orifice to be atomized. The atomization is
assisted by additional air jets to reduce pattern tailing and to shape the
spray pattern, as is done in air-atomized electrostatic spraying. Coating
flow can be high to medium and coating materials with low or high
viscosity can be used. Transfer efficiency for air-assisted electrostatic
systems is typically between 50% and 85%.
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Chapter Four Application Methods
* Bell and Disk Rotary Electrostatic Spraying
Rotary electrostatic systems use different principles' to charge and
atomize coating materials. Rotary systems consist of quickly spinning
bell- or disk-shaped components. Coating materials flow onto the center
of the component and the centrifugal force from rotation draws the
material to the edge. At the same time, the bell or disk component is
charged and transfers this charge to the coating materials. The coating is
then released as a spray and propelled toward the workpiece.
Bell rotary systems have cup-shaped components mounted horizontally.
The resulting spray of coating materials covers a wide area, so
compressed air is often used to help direct the particles toward the part.
Bells are often placed on reciprocators that oscillate up and down to
ensure thorough coverage of parts. Bell systems offer superior transfer
efficiency in the range of 70% to 95%.
120 KV
Electro Static
High Voltage Supply
Figure 4-8: Bell Rotary Electrostatic Spraying System.
Disk rotary systems have saucer-shaped components mounted vertically.
The resulting spray pattern is a narrow band of coating materials. Less
compressed air is used because the paint leaves the disk in a more
forward motion. Disk rotary systems are typically used on thin parts
with omega-shaped conveyor systems. The parts enter the booth and
follow a circular path around the disk and exit after making almost a
complete circle. Transfer efficiency of disk systems ranges between
80% to 95%.
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Chapter Four Application Methods
Air
Disk I
Movement
Electrostatic
High Voltage Supply
Figure 4-9: Disk Rotary Electrostatic Spraying System.
Although electrostatic spraying systems work regardless of the type of
coating material used, adjustments must be made based on the
conductivity of the paint. Solvent-based and high-solids coating
materials have a low conductive nature. These coatings accept the
charge at the point of contact with the electrode, as the fluid is atomized
into small particles. The charge does not pass between particles or into
the fluid stream. Waterborne coatings, however, are highly conductive.
As the charge is imparted to the atomized particles, it easily passes
between particles and can be carried down the fluid stream. As such, the
paint receptacle must be isolated from the electric potential so that
charges applied to waterborne paints are not carried away to a ground.
Electrostatic spraying methods have increased transfer efficiency, while
still maintaining the versatility and flexibility of traditional spraying
methods. The improved transfer efficiency is due to the electrostatic
force on the coating particles influencing the path they follow. The
attraction between the negatively charged coating materials and the
grounded workpiece causes more of the atomized material to hit and coat
the work surface. The influence of the electrostatic force depends on the
size and speed of the coating particle, and the air environment in the
spray booth. Smaller and slower particles are more likely to be directly
attracted to the part. Larger particles with high speeds have high
momentum and are less receptive to the electrostatic forces; these
particles are beneficial in coating corners and crevices where charged
particles tend to miss. Overspray particles are attracted to the back of the
workpiece further increasing transfer efficiency and reducing wasted
paint.
Operator technique of manual electrostatic spray application
technologies is critical to proper coating. The operator controls the
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Chapter Four Application Methods
distance from the gun to the surface, speed of each stroke, pattern
overlap, spray gun angle, and timing of triggering. All of these
parameters contribute to successful application of the coating materials
and how much coating material is wasted. Automated systems with
fixed guns mounted on reciprocators or guns mounted on movable robots
alleviate some of the inconsistency in applying coatings with spray
technologies.
Like traditional spray application, electrostatic spraying occurs in
enclosures to help confine the coating material that does not deposit on
the workpiece. Spray booths have equipment designed to control
airflow. An exhaust system pulls paint-laden air through a filtration
device that captures excess atomized particles. Dry filter booths are most
common. These booths have cloth or polymer mesh filters to capture
coating materials in the exhaust air. Often, a series of progressively
tighter filters are used to remove larger, then smaller atomized particles.
Filters must be replaced when clogged with coatings, and may be
classified as a hazardous waste depending on the type of coating material
used. Additional equipment may be required to control the release of
emissions from the organic solvents in the coating material. Spray
booths can allow movement of parts by conveyor or trolley if necessary.
All equipment used in an electrostatic spray system, such as conveyors,
air and fluid lines, and most importantly, the operator, must be grounded
to prevent a build up of excess electrical charge. While these
components should not be grounded better than the parts to be painted,
the grounding is necessary to prevent a static discharge and a spark that
can cause a fire or explosion.
To clean electrostatic systems, the fluid coating materials are exchanged
with solvent or water. The electrode is disconnected from the power
source and the gun is triggered to flush coatings from the system.
Coating must also be removed from other grounded equipment such as
hooks or hangers, conveyors, and booths. Excess coating materials on
these surfaces will prevent a ground from being maintained.
Electrostatic spray systems offer an improvement over traditional spray
systems. The electric potential between the coating material and parts
increases the amount of material that deposits on the part. Much less
paint is wasted during their use. However, electrostatic spray systems
atomize the solvents contained in the coating material, which increases
their evaporation. This increased evaporation rate creates more air
pollution burdens than other application methods. Electrostatic spraying
systems are not specifically regulated, although they are recommended
for meeting some air pollutant restrictions (40 CFR Part 63 Subpart GG).
NOTES
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Chapter Four Application Methods
The major source of pollution from electrostatic spraying applications is
due to poor transfer efficiency. For most electrostatic spray systems,
only about two-thirds of the coating material used actually ends up
coating the workpiece. A significant amount of coating material is
wasted during these processes. Since the coating material then falls on
filters, masking materials, clothing or elsewhere, additional waste is
created when these items are disposed or cleaned.
Electrostatic spray systems are considered a pollution prevention
opportunity for organic finishing facilities. Electrostatic spray systems
improve on the transfer efficiency of traditional spray systems, making
them more desirable. Additional pollution prevention can be achieved
from electrostatic spray systems by taking measures to improve the
transfer efficiency of the system. Equipment changes from air-atomized
spray systems to airless, air-assisted airless, or rotary spray systems,
which have less atomization, improve transfer efficiency of coating
materials.
Proper operation of electrostatic spray equipment can also improve
transfer efficiency and reduce waste. Reducing the pressure of
compressed air leaving the gun reduces the forward velocity of the
particles so they are less likely to rebound off the part. Lower air
pressure also reduces energy demand for the compression system.
Adjusting the air current velocity in spray areas, especially if automated
spray systems are used, will prevent atomized coating particles from
Straying from the workpiece. Spacing parts closer together on conveyors
helps stray coating particles deposit on parts. Finally, training operators
to manipulate spray equipment properly can provide much improvement.
Spray gun movement must be compatible with the fluid spray rate. The
spray gun should be held about twelve inches from the part and
perpendicular to the work piece surface. The spray pattern should be
adjusted to be slightly smaller than the part profile. The spray gun
should be triggered at the correct time on leading and trailing edges.
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Chapter Four Application Methods
Section 3
Eleetrocoatiiig
Electrocoating (also known as electrodepostion, electrophoretic
deposition or electropainting) is an organic finishing process in which
waterborne coatings are applied to metallic substrates with the use of an
electric current. An electric potential is applied between the part and the
liquid coating which attracts the paint onto the surface of the workpiece.
Two methods of electrocoating are available: anodic and cathodic. In
anodic electrocoating, the ions of the coating materials are negatively
charged. In cathodic electrocoating, the coating ions are positively
charged. Most industries currently use the cathodic method for several
reasons. During coating application, a metallic cathode will not dissolve
into the coating solution, and the coating material more easily adheres to
contaminated areas of the workpiece. Also, the resulting finish from
cathodic electrocoating is more corrosion resistant, and the color of
welded areas is more consistent with the rest of the part.
Anodic
Cathodic
Paint
Bath
Figure 4-10: Anodic and Cathodic Electrocoating
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Chapter Four Application Methods
Parts used in the process are first cleaned and pretreated to improve the
adhesion of the electrocoating finish. Then, the workpiece is immersed
for a few minutes in the coating material that is heated between 60° and
90° F. Actual operating times and temperatures are dependent on the
desired coating thickness. The coating bath is agitated to keep a uniform
concentration of coating materials throughout the bath.
After being removed from the coating tank, the part is rinsed one to four
times to remove excess coating material. The part is sprayed or
immersed in tanks with either deionized water, or a permeate rinse
solution consisting of water, solvents, and salts. The rinse solutions are
constantly filtered to remove contaminants and increase bath life. An
ultrafilter is used to separate the coating material from the solvent or
water. The coating materials are recycled to the electrocoating tank and
the permeate and water is reused in the rinse cycles.
7j\
\ ElectrocoatTar
Cathodlc Part Is Negative
Anodic Part Is Positive
'*
vy,
TP
Bag
Filter
I | 1
1 Post Rinse 1
L #1 I
ump
1 1 I 1
IPostRinsel ToOven
1 #2 \
Permeate Return
I
Ultrafilter *~
H
Exchanger
i
Paint Return
Figure 4-11: Electrocoating System with Rinse Solution Recycling.
The coating applied with this method is very uniform, and the coating
thickness can be closely controlled by adjusting the operating
parameters. Because the paint completely surrounds the part and is
attracted to all charged surfaces, this method is appropriate for parts with
complex geometry and hard-to-reach areas. Electrocoating is often used
to apply a primer coat to the workpiece.
Because of the elaborate equipment that is required, electrocoating is
generally suited only for large-volume finishing. It is not suited for small
and medium sized companies that do not have sufficient throughput of
material to justify the process, or that manufacture workpieces with
several different sizes and shapes. Color change for most installations is
very slow, so 95% of electrocoat installations paint only one color.
Despite these restrictions, electrocoating is a popular metal finishing
method. Because the rinse solutions can be processed to recover coating
solids, the transfer efficiency of electrocoating applications approaches
90%.
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Chapter Four Application Methods
Electrocoating systems are a pollution prevention opportunity for organic
finishing facilities and provide several advantages over spray systems in
terms of environmental impact. Electrocoating is an acceptable method
of applying organic finishes for most industries due to the high transfer
efficiency. No regulations target electrocoating, although the
composition of the coating material must be considered. Electrocoating
systems essentially eliminate pollution and waste because they are often
closed-loop processes. Residual coatings and rinses are captured and
recycled, so overall transfer efficiency is high and wasted coating
material low. In addition, the coating material in electrocoating systems
is not atomized which reduces the evaporation of organic solvents and
reduces air emissions.
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Chapter Four Application Methods
Section 4
Roll and Coil Coating
Roll and coil coating are application methods for continuous, flat parts
processed at high speeds. Large sheets of metal pass between circular
drums which apply the coating material; these sheets, then, are formed
into cans, drums, or other simple structures.
The basic coating application operation for roll and coil consists of two
or more rollers. The feed roller will receive the coating material either
from an internal source, a reservoir underneath the roller, or a stream
from above the roller. The feed roller passes the coating material
through a series of rollers or directly to the applicator roller. As the
coating material is passed between rollers, the consistency and thickness
is more evenly distributed across the roller surface. The applicator roller
then contacts the workpiece and coats the part. Coating thickness is
controlled by the distance and pressure between the roller and workpiece.
If only one side of the substrate is to be coated, a pressure drum will be
placed on the opposite side of the workpiece; if both sides are to be
coated, a similar feed roller and application roller configuration will be
used on both.
Depending on the rotational direction of the rollers in relation to the
movement of the part, the technique is called roll or coil.
• Roll Coating
Roll coating, or direct roll coating, is configured with the rollers turning
in the same direction as the workpiece. The roller rotates
counterclockwise as the workpiece is moved from left to right. As the
part comes in contact with the roller, the coating is transferred. Because
of the pressure between the roller and the metal, this process can impart a
wavy surface to the coating layer that can be controlled by using low
viscosity paints.
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Chapter Four Application Methods
\
Fountian \YFeed)K Applicator ]
Figure 4-12: Roll Coating System.
* Coil Coating
Coil coating, or reverse roll coating, is configured with the rollers turning
in the opposite direction as the workpiece. The application roller rotates
in a clockwise direction while the workpiece travels from left to right.
As the roller and workpiece meet, the paint is literally scraped off the
application roller by the part. The high sheer resulting from the transfer
helps to smooth out the coating surface. This method is preferred over
roll coating for applying topcoats.
Applicator Roll
Feed Roll
Figure 4-13: Coil Coating System.
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Chapter Four Application Methods
Roll and coil coating systems typically combine all organic finishing
processes together. Pretreatment, primer, primer cure, topcoat
application, and final cure are found in a continuous system. The long
continuous sheets travel on a conveyor through each stage of the process
as a take-up roll at the end captures the finished product. Roll and coil
lines operate almost year round due to the continuous feed of metal into
the system. Applicator rollers are usually gelatin-rubber or urethane-
coated metal. Other rolls are polished steel or chromium-plated steel.
Both solvent and waterborne coatings can be used in this process.
Rollers can be damaged easily, which will effect coating quality and
require expensive replacement. Part shape is limited to flat continuous
sheets or webs. However, the transfer efficiency is near 100% for both
methods, as coating materials not applied stays on the roller. No material
is wasted except when the equipment is emptied and cleaned.
Roll and coil operators have a few environmental issues to consider.
Roll and coil systems use a large volume of coating material in a
continuous flow. This creates some concerns with the evaporation of
solvents and adverse air emissions. Roll and coil coating operations are
specifically regulated under 40 CFR Part 60 Subpart TT - Standards of
Performance for Metal Coil Surface Coating, with specific VOC
emissions limitations depending upon the use of control devices. For
facilities that do not maintain control devices, the VOC emissions must
not exceed 0.28 kilograms of VOC per liter (kg/L) of coatings applied
for each calendar month; for facilities that continuously use emission
control devices, the VOC emissions must not exceed 0.14 kg/L for each
calendar month. Alternatively, facilities may show that the VOC
emissions of coatings as applied is reduced to less than 10% of their
initial amount (a 90% reduction in VOC emissions).
As part of the Clean Water Act, Effluent Guidelines and Standards for
Coil Coating (40 CFR Part 465) have been established that limit
concentrations of heavy metals, toxic organics, and conventional
pollutants in wastewater streams. The regulation is based on the type of
metal being coated (e.g., aluminum, steel, etc.) and covers wastewater
generated from all processes in the facility. The organic solvents often
contained in liquid coatings used with roll and coil coating application
methods may be classified as toxic organics. These materials can enter
the wastewater when cleaning coatings from containers or equipment.
Other wastewater may be generated during cleaning or surface activation
stages prior to applying the coating material. Actual limits for effluent
constituents are dependent on the size of the operation and the amount of
wastewater generated from the facility.
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Chapter Four Application Methods
Overall, roll and coil coating applications create very little pollution and
offer pollution prevention over traditional spray systems. Roll and coil
systems are typically closed-loop systems and run continuously without
needing to be adjusted or cleaned. Coating materials are recirculated,
leading to high transfer efficiency and little waste.
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Chapter Four Application Methods
Section 5
Dip, Flow, and Curtain Coating
Dip, flow, and curtain coating processes apply liquid organic coatings to
parts in high throughput operations. Coating materials can be applied
quickly to a workpiece by dipping or showering it as moves through the
process. Control of operating parameters including temperature,
conveyor speed, and viscosity ensure proper coating properties and film
thickness.
* Dip Coating
In dip coating, parts are suspended from a conveyor. The parts are
immersed in a bath filled with liquid coating material. When the part is
removed from the bath, surface tension pulls off excess coating material
that keeps the coating thickness uniform and reduces drain-off time. The
conveyor system carries the part over a drainboard to catch excess
coating that drips from the part. This material drains back into the bath
reducing waste. The tanks, which hold the liquid coating, typically have
agitation devices to keep the coating material consistent throughout the
bath. When not in use, lids cover the tanks, which help reduce
evaporation of solvent.
This process is most effective at coating simple geometric parts that do
not have "cupped" areas. Cupped or recessed areas facing down will
trap air when lowered into the tank, leaving the inside surface uncoated.
Cupped areas facing up will hold coating material while the part is being
removed from the bath. Frequent color changing is difficult and costly
because separate coating tanks or holding tanks are required. However,
this process has a transfer efficiency of approximately 95%. Parts are
thoroughly coated with one dip and excess coating material drains back
into the tank.
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Chapter Four Application Methods
Figure 4-14: Dip Coating System.
* Flow Coating
Flow coating involves pumping liquid coating materials around moving
parts without atomizing the coating stream. In an enclosed area, coating
material is pumped from a reservoir through nozzles stationed at various
distances, heights, and angles. The paint is showered into the center of
the enclosure where the parts move while suspended from a conveyor.
Excess material that misses a part or drips off a part is collected at the
bottom of the enclosure and circulated back into the system for reuse.
Part complexity is not an issue with flow coating as the nozzles can be
configured to reach all sides of a moving part. This process can limit
coating application to either exterior or interior surfaces depending on
the timing and locations of the nozzle spray. However, the part should
be positioned so that coating material is not trapped in recesses, but can
flow downward to be recovered. Transfer efficiency for flow coating
processes can reach 95%.
+ Curtain Coating
Curtain coating is a specialized flow coating process. Instead of a
random showering of coating material, a continuous falling sheet of
liquid material is used to coat parts. The part, typically a flat panel with
NOTES
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Chapter Four Application Methods
no recesses, is held in a horizontal position while passed under the
curtain on a conveyor. To create the curtain, organic coating is pumped
from a supply reservoir through a filter to a coating head over the
conveyor. When the head is full and reaches the overflow level, it flows
over the length of one side as a curtain. A basin collects and returns any
excess material back to the reservoir tank.
Control of the pumping process is necessary to prevent breaks in the
curtain that would result in uncoated part sections. For high quality
coating characteristics, solvent-based coatings are preferred. This
process has fast throughput rates, and is flexible enough to apply
multiple layers. Two or more coating layers can be applied in one pass.
However, the mixing of coating materials in the collection basin may
prevent recovery and reuse. Transfer efficiency can reach above 90%
with this method if coating materials are collected and reused.
Liquid Level
Reservoir
Figure 4-15: Curtain Coating System.
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Chapter Four Application Methods
Overall, dip, flow, and curtain coating methods offer several advantages
over other coating application methods. Most types of coating materials,
including high-solids coatings, can be used either with dip, flow, or
curtain coating methods. Coating thickness is more uniform and
controlled since the methods depend on timing of conveyor speed and
paint flow rate rather than operator ability. The equipment does not
require excessive maintenance, although color changes require separate
holding tanks. Most importantly, these methods have superior transfer
efficiencies as compared to traditional spraying application methods.
Dip, flow, and curtain coating offer facilities a pollution prevention
opportunity. Dip, flow, and curtain coating systems are often closed-
loop processes that essentially eliminate pollution and waste. Coatings
that do not adhere to parts are collected in catch basins and recirculated
for future use, so overall transfer efficiency is high and wasted coating
material low. The motion of the coating materials through the systems
may increase the volatilization of solvents within the coating material,
but the rate is much less than that of spray systems.
Pollution prevention tactics can be used when using dip, flow, or curtain
systems. Additional waste reduction is achieved by increasing the drain
time and area for the parts after they have been coated. This allows
excess material to return to the collection basin. If multiple coatings are
used in a single system, steps should be taken to prevent coatings from
mixing together. Increasing the distance between the streams and having
separate catch basins for each will keep the different coating materials
separate and allow them to be recirculated.
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Chapter Four Application Methods
Section 6
Powder Coating Methods
Powder coating materials have their own class of application methods.
Because they are in dry form and not liquid, powder coating materials
cannot be applied with traditional coatings methods and equipment.
However, powder coating application methods are designed to provide
high transfer efficiency and achieve good coating coverage. Powder
coating techniques include electrostatic powder spraying, flame spraying,
powder flocking, fluidized bed coating, and electrostatic fluidized bed
coating.
* Electrostatic Powder Spraying
Electrostatic powder spraying is similar to traditional electrostatic
spraying of liquid coatings. Powder coating materials are pumped from a
hopper through hoses to a modified spray gun. An electrode imparts a
negative charge to the coating particles as they exit the gun that helps to
attract them to the grounded workpiece.
Figure 4-16: Electrostatic Powder Spraying System.
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Chapter Four Application Methods
* Flame Spraying
Flame spraying techniques are similar to electrostatic powder spraying
systems, but heat, instead of an electric charge, is supplied at the gun tip.
The powder is blown through a flame where it is partially melted and
projected towards a preheated substrate. The melted particles adhere to
the part and begin to form a film immediately.
* Flocking
Flocking application methods are similar in theory to flow coating of
liquid materials. Powder coatings are mixed with compressed air and
pumped through guns. The powder coating flow is distributed around
the preheated workpiece. When the powder coating particles contact the
heated surface of the part, they begin to melt and adhere.
* Fluidized Beds
In fluidized beds, powder coating. materials are placed in an open
container. Air flows into the container through a ceramic filter at the
bottom, suspending the dry particles in the container. Parts are heated
slightly and dipped into the container. The particles that touch the part
are partially melted, coating the surface of the workpiece. Coating
thickness is difficult to control because particles touch and melt in
random locations.
Figure 4-17: Powder Coating Fluidized Bed System.
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Chapter Four Application Methods
* Electrostatic Fluidized Beds
Fluidized beds can also incorporate electrostatics to assist in coating. An
electric charge is applied to the coating materials as they pass above the
ceramic filter. This method does not require the part to be preheated, and
coating thickness is more controllable by the amount of charge given to
the particles.
One major advantage of powder coating application methods is the high
transfer efficiency. Unmelted powder coating materials that do not
adhere to the part can be collected and reused. Electrostatic powder
spraying and flocking are typically performed in enclosed booths with
vacuum systems to capture powder that does not adhere to the part. The
powder is returned to the hopper for reuse. Fluidized beds retain the
powder materials within the system much like dip tanks used with liquid
coating materials. Melted powder coating materials from flame spraying
methods cannot be reused. Overall, transfer efficiencies for powder
coating spray applications approach 95% to 100%. In addition to the low
material waste, the extremely low volatile organic content of powder
coating materials virtually eliminates any air emissions during their
application. Care must be taken to avoid mixing different powder
coating types if applied using the same equipment or in sequential
systems. Mixed powder coatings materials usually cannot be reused.
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Chapter Four Application Methods
Section 7
Environmental Considerations for
Application Methods
Application methods for organic finishing share common environmental
issues. Regulatory violations and sources of pollution among the various
technologies are found to be very similar. Pollution prevention tactics
can be followed by organic finishing facilities regardless of the
application method used. Many environmentally related problems stem
from the type of coating material used and its solvent content, rather than
from the specific type of application method being used. Environmental
issues concerning the coating materials are discussed here briefly.
Regulatory Requirements
Except as noted in the previous sections, application methods have few
direct restrictions from environmental regulations. Facilities should be
aware of a few general regulations under the main environmental acts.
* Air
The Clean Air Act regulates the emission of volatile organic compounds
(VOCs) (40 CFR Part 60) and hazardous air pollutants (HAPs) (40 CFR
Part 61 and 40 CFR Part 63). 40 CFR Part 60 covers organic finishing
for metal furniture, automobiles and light duty trucks, large appliances,
coil coating, and beverage can industries. 40 CFR Part 63 restricts HAP
from the aerospace and shipbuilding and ship repair industries.
Depending on the solvent content and the volume of coating material
used, solvents can evaporate and produce sufficient VOC and HAP
emissions to subject an operator to major source requirements and Title
V permitting requirements. If VOC emissions cannot be eliminated
completely, they must be controlled. Air pollution control equipment,
such as recovery or incineration units, is often found with the ventilation
associated with application equipment. These units capture VOCs prior
to their release into the atmosphere.
NOTES
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Chapter Four Application Methods
+ Water
As part of the Clean Water Act, Effluent Guidelines and Standards for
Metal Finishing (40 CFR Part 433) have been established that limit
concentrations of toxic organics in wastewater streams. The organic
solvents often contained in liquid coatings used with various application
methods may be classified as toxic organics. These materials can enter
the wastewater from liquids (water or solvents) used to clean containers,
equipment, or work areas. Actual limits for effluent constituents depend
on the size of the operation and the amount of wastewater generated from
the facility. If the facility discharges directly to receiving waters, these
limits will be established through the facility's National Pollutant
Discharge Elimination System (NPDES) permit (40 CFR Part 122).
Facilities which are indirect dischargers releasing to a publicly owned
treatment works (POTW) must meet limits in the POTW's discharge
agreement. Wastewater streams with concentrations exceeding permit
limits will require pretreatment prior to discharge to receiving waters or
to a POTW. Pretreatment may include separation of liquid wastes to
remove solvents, and settling or precipitation of solid materials.
+ Solid and Hazardous Waste
Under the Resource Conservation and Recovery Act (RCRA), organic
finishing facilities are required to manage listed and characteristic
hazardous wastes (40 CFR Part 261). Depending on their formulation,
coating materials may contain constituents listed or characterized as
hazardous wastes. Materials contaminated with the coatings, such as
spray booth air filters, masking materials for fixtures and floors, and rags
or containers used when cleaning, may require treatment as hazardous
waste. Hazardous waste management (40 CFR Part 262) includes
obtaining permits for the facility in order to generate wastes, meeting
accumulation limits for waste storage areas, and manifesting waste
containers for off-site disposal. Responsibilities will vary according to
the amount of hazardous waste material generated; facilities generating
at least 100 kilograms of hazardous waste per month must comply. Each
state and/or region is primarily responsible for the regulation of non-
hazardous solid wastes (those not governed by the hazardous waste
provisions of RCRA). Check with state environmental agencies for
specific information or guidance.
NOTES
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Chapter Four Application Methods
Common Causes of Violation
The air emission regulations may be violated if evaporated solvents
classified as volatile organic compounds and/or hazardous air pollutants
are allowed to accumulate above limits allowed by the Clean Air Act.
Ventilation and exhaust systems must operate properly to ensure the
vapors are removed from the application area. Adequate fresh air
volumes must circulate and any particulate filtration devices must not be
clogged. Air pollution control equipment should be attached to exhaust
systems to recover or destroy volatile organic compounds instead of
releasing them to the air.
Wastewater can easily become contaminated with coating materials or
cleaning solvents. This may occur with the use of waterwash spray
booths, disposal of materials, or accidental spills of coating material or
wash solutions. Contaminated water streams may contain pollutants in
concentrations exceeding limits established by facility NPDES permits or
POTW discharge requirements. As a result, effluent, may not be directly
released to water systems or to POTWs without pretreatment.
Materials that contact coating waste or cleaning solution must be handled
accordingly. If the materials are classified as hazardous, they must be
properly stored, manifested and disposed according to RCRA standards
for hazardous waste (40 CFR Part 262).
Sources of Pollution
Specific sources of pollution have been covered in more detail in each
section previously. With all types of application, pollution is created
from two main areas - wasted coating materials and cleaning processes.
Coating material that is not used to coat parts and cannot be captured and
reused is the major source of waste. Spray applications with the lowest
transfer efficiency create the most wasted coating material. The other
methods allow excess material to be collected and reused on other parts.
Cleaning must be done periodically to all equipment and work areas.
Cleaning solutions and tools such as brushes or rags must be discarded.
Again, higher volumes of cleaning waste is associated with spray
systems that must be cleaned more frequently and thoroughly.
Continuous application systems, such as dip, electrocoating, and roll
coating, do not require as much cleaning and therefore produce less
waste.
NOTES
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Chapter Four Application Methods
Pollution Prevention Alternatives
Numerous pollution prevention alternatives are available for application
processes to reduce waste. The most effective is to change to an
application method with higher transfer efficiency. Switching from
traditional spray systems to dip, flow, or powder methods greatly reduces
the amount of pollution and waste created. This is not always feasible
due to part constraints, facility restrictions, or personnel requirements,
not to mention the associated capital costs. Several actions can still be
taken without changing equipment that will reduce facility pollution and
waste.
• Material Substitution
First, facilities should evaluate the coating material currently used and its
solvent content. Lowering or eliminating solvent in the coating material
will greatly reduce air pollution, wastewater problems, and solid waste
restrictions. Solvent thinners can be reduced by using heat to lower the
viscosity of coating materials.
* Materials and Waste Handling and Storage
If the type of coating material cannot be changed, proper handling of the
materials will help reduce waste. Large containers of the material, such
as dip tanks or collection basins, should be covered whenever possible to
reduce evaporation of solvents and prevent contamination by dirt and
other debris. Non-hazardous coating solids and water should be
segregated from hazardous solvents and thinners, and containers labeled
to prevent mixing. Separation of the materials reduces the amount of
hazardous waste that is produced. Coating material solids can be dried
and treated as a solid waste for disposal in a landfill.
* Operations and Procedures
Next, operational changes can reduce waste. Schedule paint jobs to
minimize changing colors in equipment. If several colors are required,
use a different set of equipment for each individual color rather than
cleaning equipment with solvents each time a new color is used. If extra
equipment is not an option, schedule painting with light colors first, then
darker ones; lighter coating does not need to be completely removed
from the equipment, but can blend into the darker coating. Pre-inspect
parts to eliminate rejects prior to painting. Orient parts properly to
minimize recessed areas that would hold excess coating material.
NOTES
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Chapter Four Application Methods
* Maintenance and Housekeeping
Facilities should perform regular maintenance and housekeeping.
Regular inspection and maintenance of equipment will assure that valves,
regulators, gauges, and other monitoring devices are working properly
and providing consistent coating. Keeping painting areas clean will
allow improper coating techniques and equipment leaks to be observed
and fixed quickly. Accidents can also be prevented. Regular cleaning is
also essential to pollution prevention. Cleaning will remove coating
materials from equipment to prevent drying and clogging of hoses,
valves, and pipes. Water should be used for cleaning when possible to
reduce the amount of organic solvents used and amount of hazardous
waste generated. Perform the initial flush of application equipment with
used solvent, saving fresh solvents for final cleaning stages. When
cleaning, point spray guns and drain tank residues into an enclosed area,
such as a barrel or can, to capture coating materials, and solvents.
* Training
Finally, properly trained employees are essential to any pollution
prevention plans. Train employees on the correct operating procedures
for application methods. This will reduce reject parts, wasted coating
materials, and damage to equipment. Train employees on safe handling
of materials and wastes and encourage continuous improvement.
Training familiarizes workers with their responsibilities, which reduces
spills and accidents.
NOTES
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Chapter Four Application Methods
Section 8
Chapter Summary
The application technologies discussed in the chapter are summarized in
Table 4-1. These six methods are quite common in the organic finishing
industry although new methods are being developed. Methods such as
supercritical fluid spraying or autodeposition increase transfer efficiency
while maintaining good coating characteristics. The table also provides
the coating materials and part geometries typically used with each
application. The combination of coating material, part geometry, and
production variables must be considered when developing an application
system. Ranges of transfer efficiency are also provided in the table to
give a quick comparison of the different methods.
The application process is essential to providing the proper coating on a
workpiece, but it also contributes a good amount to the environmental
concerns of an organic finishing facility. Air pollution from volatile
organic compounds is the main issue for facilities. VOC emissions can
be reduced in two ways: use coating materials with fewer VOCs or use
less coating material. Some application methods restrict the type of
coating materials that can be used, so lowering VOCs in the coating
material may not be possible. But the technologies can be used to
increase transfer of the material to the parts with less waste. The
application methods discussed here cover a wide range of transfer
efficiencies.
NOTES
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Chapter Four Application Methods
Table 4-1: Typical Organic Finishing Application Methods.
APPLICATION
METHOD
Spraying
Air-atomized
Airless
Air-assisted Airless
HVLP
Electrostatic Spraying
Air-atomized
Airless
Air-assisted Airless
Rotary
Electrocoating
Dip, Flow, and Curtain
Roll and Coil
Powder Coat Methods
TRANSFER
EFFICIENCY
15%-40%
20%-50%
30%-60%
30%-75%
40%-80%
40%-70%
50%-85%
70%-95%
90%-98%
90%- 100%
95%- 100%
95%-100%
COATINGS
USED
For each:
Solvent-based
High-solids
Waterborne
For each:
Solvent-based
High-solids
Waterborne
Waterborne
Solvent-based
High-solids
Waterborne
Solvent-based
High-solids
Waterborne
Powder
PART
GEOMETRY
For each:
Simple to
complex
Large areas to
small parts
For each:
Simple to
complex
Large areas to
small parts
Simple to
complex
Medium to
small "parts
Flat panels or
simple
Medium to
small parts
Flat continuous
sheets
Simple to
complex
Large to small
NOTES
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CHAPTER FIVE
CURING METHODS
Curing is the final stage of the organic finishing process. Curing has two
stages. The first is the removal of the solvent or diluent through
evaporation so that the coating is no longer wet to the touch. This is
often called drying. The second stage is the actual curing, during which
the resins or binders in the coating material are undergoing a chemical
reaction. The reaction causes crosslinking between the resin molecules
and renders the coating film relatively inert to the environment. Li the
curing of powder coating materials, because no solvent or diluent is there
to be removed, only the second stage occurs.
Regardless of the type of technology used, curing equipment generates
thermal energy that is absorbed by the coating and part. The curing stage
elevates the workpiece and coating to a particular temperature and holds
that temperature for a set period of time. The combination of
temperature and time serves to evaporate solvents and set the coating.
Temperature and exposure times are carefully monitored to ensure
proper curing and drying. Extended baking or exposure to heat sources
may impair the coating characteristics.
If ambient air conditions permit, curing of low-solvent coatings can be
completed in open areas. No heat is generated or supplied to the area,
but air circulation may be enhanced by blowers and fans. Open air
curing is often done during the warmer summer months.
The type of curing method employed is often dictated by the coatings
materials used. Air dried coatings are defined by the EPA as those that
cure at room temperatures, while those that cure at temperatures up to
194° F are classified as forced-air dried. Baked coatings require a curing
stage at temperatures above 250° F. Others coatings are classified as
radiation curable. The curing occurs when the part and coating are
exposed to infrared, ultraviolet, microwave, or other radiation.
Two common curing technologies are convection ovens and infrared
radiation systems. Both provide consistent curing of many different
coatings. This chapter describes each of these systems and their
environmental issues.
NOTES
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Chapter Five Curing Methods
Section 1
Convection Oven Curing
Convection ovens are used in organic finishing for curing and drying.
Some solvent-based paints require heated drying and curing, while most
waterborne and powder coatings demand it. Industrial convection ovens
are designed to move heated air around an enclosed area. The heat
accelerates the release of vapors and the formation of chemical bonds to
create the final coating surface.
Convection ovens consist of large metal, brick, or ceramic housing
Structures where heated air circulates. The heat can be generated by
electricity, gas, or other energy sources. Typical temperatures for ovens
used in metal finishing processes range from around 100° to 500° F and
baking times range from a few minutes to an hour.
Figure 5-1: Convection Oven Curing System.
Air from the oven is continually recirculated to the heater unit or
exhausted. The exhaust system removes excess volatile organic
compounds released from the paints and eliminates any smoke build up
NOTES
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Chapter Five Curing Methods
inside the oven shell. Additional equipment may be needed with the
exhaust system to capture harmful vapors before they enter the
atmosphere.
Convection ovens can be a batch system where parts remain stationary
and are placed in and removed from the chamber at various times.
Ovens can also be continuous systems where parts move through the
heated area on a conveyor or overhead trolley.
Two types of gas convection ovens are direct-fired and indirect-fired. In
a direct-fired oven, the heated air and combustion products pass over the
parts. If the combustion products would adversely effect the coating
characteristics, an indirect-fired oven must be used. In indirect-fired
ovens, the combustion products do not directly come in contact with the
parts. Instead, air in the heating chamber is passed through a heat
exchanger to heat the oven area where the parts are contained. Indirect-
fired ovens can require a third more energy than direct-fired systems.
Using convection ovens for curing is not restricted by part geometry.
Because the entire mass of the part is heated to the required temperature,
the paint is cured on all surfaces. Larger or more complex parts,
however, may need to remain in the oven for a longer period of time than
smaller, simpler parts. Cooling may be required after a part leaves an
oven before it can be handled or be processed further.
Convection ovens, depending on their design, are not as energy efficient
as radiation systems. Heat is easily lost through the doors (i.e., where
parts enter and exit) and oven walls, when heated parts exit, and through
exhausted air.
NOTES
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Chapter Five Curing Methods
Section 2
Infrared Radiation Curing
Radiation systems cure organic coatings by supplying heat in the form of
wavelengths. Infrared (IR) radiation is the most prevalent form of
radiation curing, although ultraviolet light, microwaves or radio waves
are also used. The transfer of heat energy from the emitter to the target is
precise and rapid, making radiation curing popular in organic finishing
systems.
In infrared systems, different wavelengths correspond to different
temperatures. Long wavelengths produce temperatures up to 500°F,
while short wavelengths can emit temperatures up to 4000°F. As the IR
waves are directed at a coated part, the thermal energy is absorbed by the
coating or substrate to accelerate the curing and drying of the coating
materials.
Depending on the wavelength of infrared radiation emitted, different
components of the target absorb the energy. Long wavelengths are
absorbed slowly by the coating at the surface; the rate of absorption is
the same as that in a convection oven. These long wavelengths will
eventually heat the whole mass. Medium length IR radiation heats the
coating from the center with some losses by conduction to the metal
substrate or the air. Use of medium wavelengths is most efficient
because the coating receives the most thermal energy. Short wavelength
radiation will penetrate the coating and heat the substrate directly, which
will eventually heat the coating by conduction. Coatings that may be
adversely effected by heat should be cured with short wave radiation to
avoid surface defects, such as bubbling or blistering.
Long-Wave
Heats Surface
1
! ~\ \
I I
Medium-Wave
Heats Coating
i
Coatina ( ^ (
1 4
Substrate
Short-Wave
Heats Metal
1
tv-t
) J
Figure 5-2: Absorbtion of Infrared Radiation by Coating Materials.
NOTES
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Chapter Five Curing Methods
The choice of wavelength is based on. the polymer or resin and the
pigment color. The infrared wavelength should be set in a range that will
be absorbed by the resin so that crosslinking and bonding of the
molecules will occur. At the same time, the infrared wavelength must
also be absorbed by the color of the coating instead of scattered.
Typically, wavelengths greater than 5.5 nanometers are effective. Some
coating materials have been specially formulated to cure with IR
radiation; however, conventional coatings can be used with infrared
heaters once the optimal wavelength for absorption has been determined.
The design of infrared heaters varies based on the wavelength and
intensity of the radiation emitted. Short waves with high intensity are
created with quartz tubes. External reflectors of gold or ceramic direct
the waves toward the product. Medium length waves with medium
intensity can be formed with wide, flat type coils covered with quartz or
ceramic. Alternatively, metal rods or quartz tubes, with or without
reflectors, can be used. This configuration allows rays to be directed
precisely or packed closely in smaller, controllable zones. Long
wavelengths at low intensity are emitted from electric metal-faced or
fiberglass panels, or ceramic cylinders on reflectors. For long
wavelengths, another option is gas heaters that chemically catalyze the
gas on a surface instead of burning it; this typically creates a combination
of convection and low intensity IR radiation.
Figure 5-3: Infrared Radiation Coils.
To achieve good results, infrared curing systems must be properly
designed and the operating parameters optimized. In addition to the
NOTES
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Chapter Five Curing Methods
choice of wavelength and time, the infrared ray emitters and the part
must be arranged properly. Infrared curing is a line-of-sight process, so
heat only reaches areas where the radiation is directed. Parts in sheets or
simple forms work well with IR curing. Bends, corners, and recesses of
complex parts may be missed by the wavelengths. Careful configuration
of the emitters and orientation of the part can reduce areas in shadows
and allow complete curing. One benefit of this attribute is that if only a
portion of a part is coated, only that section needs to be exposed to the IR
rays.
Infrared curing is more efficient than conventional convection oven
curing due to several reasons. First, the transfer of heat energy to a part
is much faster with IR rays than with heated air. Second, when using
infrared systems, specific layers of the workpiece are heated to focus the
energy on the proper target, as compared to convection ovens where both
the coating films and workpiece substrates must be heated to achieve
thorough curing. Third, infrared systems must only heat the coating
layer to the curing temperature; but in convection ovens, the entire part
must reach the curing temperature to ensure good coating results.
Often, infrared curing is used in conjunction with convection oven
curing. The IR system is used to bring the workpiece up to the curing
temperature very quickly. Then, the part enters a convection oven where
the heated air ensures that all surfaces, especially on complex parts, are
fully cured and dried. This dual system allows for simple configuration
of the IR heater.
NOTES
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Chapter Five Curing Methods
Section 3
Environmental Considerations for Curing Methods
Curing methods typically do not contribute significant environmental
burdens to organic finishing facilities. Most concern is from the type of
coating material used. Excess solvents in the coating material that
evaporate during the curing stage must be captured to prevent air
pollution. Curing systems do require large energy inputs, so
consumption of electricity or natural gas is an issue.
Regulatory Requirements
Air
The Clean Air Act regulates the emission of volatile organic compounds
(VOCs) (40 CFR Part 60) and hazardous air pollutants (HAPs) (40 CFR
Part 61 and 40 CFR Part 63), and provides specific standards of
performance to control emissions from various types of coating
operations (40 CFR Part 60). Depending on the solvent content of the
coating material applied, sufficient VOC and HAP emissions could
develop during curing operations to subject an operator to major source
requirements and Title V permitting requirements. The Act also
regulates the formation of nitrogen oxides (NOx) from combustion
sources; however, emissions of NOx are often well below compliance
levels for small operations.
Controlling VOC emissions can be accomplished in two ways. A
coating material with a lower VOC content can be used. Otherwise, air
pollution control equipment is required on curing exhaust systems to
recover or incinerate the VOCs and HAPs before they are released from
the facility. Controlling NOx emissions can be achieved by adding
oxidation systems, scrubbers or adsorbers to the exhaust system if
necessary.
Common Causes of Violation
Emission of volatile organic compounds or hazardous air pollutants from
heating structures may occur and exceed limits allowed by Clean Air Act
NOTES
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Chapter Five Curing Methods
Title V permits. The quantity of VOCs or HAPs released from the
curing depends on the amount of organic solvent in the coating
formulation. These emissions in the exhaust air stream can be captured
and treated to prevent their release to the atmosphere. Common air
pollution control tactics include solvent recovery, solvent incineration,
and solvent concentration.
Emission of nitrogen oxides (NOx) may occur and exceed limits allowed
by Clean Air Act Title V permits. The quantity of NOx formed depends
on the amount of combustion products and evaporated diluent that
combine and come in contact with a direct flame.
Sources of Pollution
The biggest source of pollution from curing systems is air pollutants.
Volatile organic compounds and hazardous air pollutants may be
released from the coating material, depending on the formulation.
Emissions of nitrogen oxides (NOx) may be produced when products of
combustion and curing contact a direct flame. A major concern is
inefficiency in curing systems. Heat loss through oven doors, heated
work pieces, poorly insulated walls, and improperly sealed panels uses
additional energy. Finally, poor circulation of heated air and improper
alignment of infrared heaters can result in unacceptable finish on the
parts. The parts become waste, or must be reworked.
Pollution Prevention Opportunities
A few pollution prevention opportunities are available to improve curing
system operations. Volatile organic compound and hazardous air
pollutant emissions can be reduced by using powder coating or
waterborne coating formulations where possible, rather than solvent-
based coating materials. Nitrogen oxide (NOx) emissions can be
reduced by introducing fresh air into the combustion chamber. Fresh air
will lower the flame temperature and prevent NOx formation. Heat loss
can be reduced by improving insulation of the structure, and sealing
panel joints. Proper curing can be achieved consistently by monitoring
airflow circulation systems for accurate operation in convection heaters.
In radiation systems, proper curing can be achieved by optimizing the
wavelength, exposure period, and part arrangement. Curing can also be
improved by introducing air into the system to distribute latent heat more
evenly across part surfaces.
NOTES
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Ckapter Five Curing Methods
Section 4
Chapter Summary
Curing systems complete the process for manufacturing workpieces with
an organic finish. The heated cycle dries the coating material by
promoting the evaporation of any liquid solvents or water. It also
provides the thermal energy necessary for the binders in the coating
material to form bonds and adhere to the part surface. Typical curing
systems include convection ovens and radiation heaters. Convection
ovens heat the air surrounding parts to cure the coating. Radiation
heaters, such as infrared radiation systems, use energy at different
wavelengths that are absorbed by the coating material to cause the
curing.
Curing systems themselves create a minimal amount of environmental
burdens for organic finishing facilities. All systems require a large
energy input, and thus consume natural resources. Convection ovens
using natural gas may create nitrous oxide emissions. The biggest source
of pollution is from the coating material used. High solvent coatings will
evaporate during the curing stage. These air pollutants must be captured
for recovery or incineration instead of being release to the atmosphere.
NOTES
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CHAPTER SIX
SELF-AUDIT PREPARATION GUIDE
This chapter provides information to assist organic coating facilities in
preparing for an environmental audit and is divided into several sections
based on the type of pollution or waste. Each section has a list of
records to review, such as plans, monitoring data, and inventory lists.
Specific areas that should be inspected are also listed. Actions required
by management, supervisors, and operators are presented. Items that
relate directly to organic finishing are also listed. Prior to conducting an
audit, facilities should identify all of the applicable environmental
regulatory requirements, including federal, state, and local requirements.
The information in this chapter provides general guidance on what
facilities need to do to prepare for an environmiental audit. EPA
encourages conducting internal audits as a way for individual facilities
to identify and address environmental issues. More specific information
on EPA's self-audit and small business policies are presented below:
Audit Policy;
* EPA's final policy on incentives for self-evaluation and self-
disclosure of violations was published in the Federal Register on
December 22, 1996 (60 FR 66706). It took effect on January 22,
1996.
* It represents a refinement of the March, 1995 Voluntary
Environmental Self-Policing and Self-Disclosure Interim Policy
Statement, which offered regulated entities powerful new incentives
to discover, disclose, and correct violations of environmental law.
NOTES
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Chapter Six Self-Audit Preparation Guide
* The goal of the voluntary self-disclosure policy is to provide an
incentive for regulated entities to self-audit, disclose, and correct
environmental violations.
» Under the final policy, the Agency will protect public health and the
environment by reducing civil penalties and by not recommending
criminal prosecution for regulated entities that voluntarily discover,
disclose, and correct violations.
* The final policy applies to violations under all of the environmental
laws that EPA administers, and will be applied uniformly across
EPA's enforcement programs and Regions.
* EPA will study the results of the policy within three years of the
effective date and make that study available to the public.
Incentives for Due Diligence, Disclosure, and Correction;
* Under the final policy, where violations are found through voluntary
environmental audits or efforts that reflect a regulated entity's due
diligence (i.e., systematic efforts to prevent, detect and correct
violations, as defined in the policy), and all of the policy's conditions
are met (see discussion of safeguards), EPA will not seek gravity-
based penalties and generally will not recommend criminal
prosecution against the company if the violation results from the
unauthorized criminal conduct of an employee.
f Where violations are discovered by means other than environmental
audits or due diligence efforts, but are promptly disclosed and
expeditiously corrected, EPA will reduce gravity-based penalties by
75% provided that all of the other conditions of the policy are met.
* EPA retains its discretion to recover economic benefit gained as a
result of noncompliance, so that companies will not be able to obtain
an economic advantage over their competitors by delaying their
investment in compliance.
* The final policy also restates EPA's practice of not routinely
requesting environmental audit reports.
NOTES
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Chapter Six Self-Audit Preparation Guide
Safeguards to Protect the Public:
4 In addition to prompt disclosure and correction, the policy requires
companies to prevent recurrence of the violation and to remedy any
environmental harm.
4 Repeated violations, or those which may have presented an
imminent and substantial endangerment or resulted in serious actual
harm, are excluded from the policy's coverage.
4 Corporations remain criminally liable for violations resulting from
conscious disregard of their legal duties, and individuals remain
liable for criminal wrongdoing.
4 The policy contains two provisions ensuring public access to
information. First, EPA may require as a condition of penalty
mitigation that a description of the regulated entity's due diligence
efforts be made publicly available. Second, where EPA requires that
a regulated entity enter into a written agreement, administrative
consent order, or judicial consent decree to satisfy the policy's
conditions, those agreements will be made publicly available-
Information regarding this policy may be obtained at the following
website: http://www.es.epa.gov/oeca/auditpol.html.
Small Business Policy:
EPA's Small Business Policy is intended to promote environmental
compliance by providing incentives like penalty waivers and penalty
mitigation to conduct environmental audits and participate in on-site
compliance assistance programs to discover, disclose and correct
violations. The policy applies to a person, corporation, partnership, or
other entity that employs 100 or fewer individuals and is specifically
tailored to small businesses. In particular, the policy:
4 Is written in plain, simple English and is concise and easily
understandable
4 Allows small businesses who have the expertise to conduct an
environmental audit and permits those who do not to obtain
government-sponsored compliance assistance to get credit under the
policy
4 Provides an extended compliance period for companies who employ
pollution prevention fixes to correct their violations
NOTES
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Chapter Six Self-Audit Preparation Guide
4 Anticipates that penalties for economic benefit will be collected
infrequently, so small businesses are more likely to get 100%
penalty mitigation
* Allows small businesses to get anonymous compliance assistance
and still get credit under the policy if they disclose their violations to
an appropriate regulatory official.
The policy also provides guidance for State and local governments to
offer these incentives. A copy of the policy may be obtained at the
following website: http://www.es.epa.gov/oeca/smbusi.html.
NOTES
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Chapter Six Self-Audit Preparation Guide
Section 1
Air Emissions
A. Records To Review
* State and local air pollution control regulations
4 Emissions inventory
4 All air pollution source permits
4 Plans and procedures applicable to air pollution control
4 Emission monitoring records
4 Opacity records
4 Notices of violation (NOVs) from regulatory authorities
* Instrument calibration and maintenance records
4 Reports/complaints concerning air quality
4 Air Emergency Episode Plan
* State and/or federal regulatory inspections
* Regulatory inspection reports
* Documentation of preventive measure or action
4 Results of air sampling
4 Pollution prevention management plan
4 Ozone depleting chemical (ODC) inventory
B. Physical Features To Inspect
4 All air pollution sources (fuel burners, VOC sources, etc.)
4 Air pollution monitoring and control devices
4 Air emission stacks
4 Air intake vents
C. Responsibilities of Supervisors and Managers
Supervisors and managers should...
D Sign all permits and compliance statements for facility operations
unless multi-facility permits are to be signed by a higher authority.
D Sign applications for permits related to demolition, pre-
construction, and construction phases of projects unless
NOTES
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multi-installation permit applications are to be signed by a higher
authority
D Sign applications and pay related fees associated with operations
permits
D Budget sufficient resources to maintain and demonstrate
compliance, including all routine air monitoring and scheduled
sampling or testing. Notify state and local authorities of all
instances of noncompliance, to conform with permit requirements
D Update air emission inventories and maintain current records of
physical, operational, and emission characteristics of air sources
D Survey emission sources to identify potential reductions
D Ensure the development of air episode plans as required, and
provide copies to the Regional Environmental Coordinator.
Cooperate with the EPA, and state and local air pollution control
authorities in the execution of air episode plans while in episode
areas
D Ensure training is provided as required by the Clean Air Act.
D. Supervisor's and Manager's Air Checklist
Regional Concerns
Q What is the attainment status of the region we are located in? What
is the probability of restrictions on air emissions limiting our ability
to accommodate new products, structure changes, or changes in
operations?
D Do we have a current air pollution emission inventory? Has it been
provided to the regulatory agency? What percentage of the regional
emissions do we account for?
D Do we maintain records and reports on Emission Reduction Credits
(ERCs)?
D Are we required to have an air pollution episode plan? Is it current?
How many times have we had to activate it in the last five years?
Stationary Sources
D How many permitted sources do we have? Have we received any
Notices of Violations or other enforcement actions?
D Do we have a program for periodic inspection of air emission
sources to assure that they are properly operated and maintained?
O Do we have a requirement in our activity environmental instruction
to ensure everyone reports to the environmental staff before
obtaining, building, or modifying equipment or processes?
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What are the emission limits and testing requirements on our...
D Boilers and other fuel burning systems?
D Maintenance and other industrial shops?
Do we have the required emissions controls on our...
D Solvent degreasers?
D Painting operations?
D Ovens?
Personnel
n Are there any requirements for licensing or certification of
operators of air emissions sources? If yes, what sources? Do our
personnel have the required certification?
D Do we have a program for training operating personnel?
E. Organic Finishing Facility Checklist
D What is the VOC content of coating materials? Do the VOC
emissions fall below levels required for my particular industry as
noted in 40 CFR Parts 60 and 63?
D Do liquid coatings come in contact with exhaust air streams? If so,
do concentrations of VOCs exceed the limits established by facility
air permits? Are air emissions from organic solvent cleaning
processes properly controlled and in compliance?
D Do powder coatings come in contact with exhaust air streams? Do
dry residual coatings and blast media come in contact with exhaust
air streams? If so, do concentrations of particulate matter exceed
the limits established by facility air permits?
D Do exhaust air streams have air pollution control equipment
attached? Is that air pollution control equipment working properly?
Does final exhaust air have concentrations of pollutants below
required levels?
D What is the transfer efficiency of the coating application system?
Does it meet requirements, if any, for the particular industry to
prevent air emissions?
NOTES
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Chapter Six Self-Audit Preparation Guide
Section 2
Wastewater Management
A. Records To Review
* NPDES Permits
* NPDES Permit applications (new or RENEWAL)
4 Discharge monitoring reports for the past year
* Laboratory records and procedures and USEPA QA results
* Monthly operating reports for wastewater treatment facilities
4 Flow monitoring calibration certification and supporting records
* Special reports, certifications, etc., required by NPDES permit
* Spill Prevention Control and Countermeasure (SPCC) Plan
* All records required by SPCC Plan
* All enforcement actions
4 NPDES state or federal inspection reports
* Sewer and storm drain layout
4 Local sewer use ordinance
4 Local service use permit
* Sewer system bypass records
4 Notification to local POTW
4 Old spill reports
4 Repair/Maintenance records for the wastewater treatment system
* As built drawings
• Federal facility compliance agreements
* Stormwater pollution prevention plan
* Pretreatment permits
* Design plans for wastewater and industrial waste treatment plants,
including treatment basins
* Utility and general site maps, diagrams, plumbing
* Pollution Prevention Plan
B. Physical Features To Inspect
* Discharge outfall pipes
* Wastewater treatment facilities
* Industrial treatment facilities
* Floor and sink drains (especially in industrial areas)
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4 Oil storage tanks
4 Oil/water separators and other pretreatment devices such as sand and
grit traps, grease traps, and sand interceptors
4 Wastewater generation points
4 Discharge to POTW
4 Streams, rivers, open waterways
* Stormwater collection points (especially in industrial and
maintenance areas)
4 Non-point source discharge areas
4 Wash areas (centralized facilities and areas in vicinity of
maintenance)
4 Catch basins, drop inlets, holding/retention ponds
4 Waste and sump collection points
4 Sludge disposal areas
4 Sewage sludge land application sites
4 Construction sites
C. Responsibilities of Supervisors and Managers
Supervisors and managers should...
D Develop program to comply with EPA regulations for industrial
activity non-point source pollution and stormwater discharge
requirements
D Cooperate with federal, state, local, and regional environmental
regulatory officials
D Reduce or eliminate wastewater treatment needs by eliminating or
reducing the volume and pollutants at the source
O Comply with permit conditions for discharge of treatment plant
sludge into navigable waters (incineration of sludge must comply
with Clean Air Act and hazardous waste requirements, and land
disposal of sludge must comply with applicable CWA and RCRA
requirements)
D Comply with all applicable pretreatment standards and local
Publicly Owned Treatment Works limits and permit requirements
D Train all personnel involved in operations that result in actual or
potential pollution of surface or groundwater.
D Provide the resources for operation performance monitoring,
sampling, and testing, as well as for maintaining and demonstrating
compliance with permit and pretreatment requirements and
maintain records of all monitoring information
D Identify and submit environmental compliance projects required to
bring wastewater . sources into compliance with applicable
requirements
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d Improve opportunities to recycle and reclaim and reuse wastewater
and sludge
D Develop, implement and maintain current stormwater management
plans for the facility, and comply with federal, state and local
regulations and permit conditions
D Ensure environmental personnel are properly trained and certified,
if required.
D. Supervisor's and Manager's Clean Water Checklist
NPDES Discharge Permits
D How many discharge permits do we have? How many discharge
points? Have we ensured that raw wastewater cannot bypass our
treatment facility/facilities?
D Are we covered by some type of stormwater discharge permit?
D Have we completed the Stormwater Pollution Prevention Plan
(SWPPP)? Have all operational best management practices been
implemented? Structural best management practices?
O Do we ensure that a construction stormwater permit covers all
construction activities that disturb .five acres or more?
D What are the general limitations and monitoring requirements?
D How many violations of permit limitations have occurred in the last
year?
D Have we received any Notices of Violations or other enforcement
actions? What corrective action has been taken? Has the violation
been closed with the regulatory agency?
D Do we have any problems with recurring violations?
Un-permitted Discharges
O Are there any other discharges that may require permits, i.e.,
stormwater outfalls, etc.?
D Have we identified site requirements for, and have in place,
properly designed oil/water separators?
D Has monitoring of our stormwater discharges indicated elevated
levels of any pollutants?
D Do we have a program to periodically inspect potential sources of
stormwater contamination?
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Discharges to POTWs
D Do we have any discharges to Publicly Owned Treatment Works
(POTW)?
D What are the types and volumes of the discharges?
D What pretreatment is required?
D Are we required to monitor these discharges?
D Are we complying with the applicable requirements?
D Are there any current or anticipated problems with our discharges?
D If no POTW is available, is one under construction? If yes, what
are our plans to connect to it?
E. Organic Finishing Facility Checklist
D Do coating materials come in contact with water streams? Do
chemical coatings removal solutions, organic solvent cleaning
solutions, or aqueous cleaning solutions come in contact with water
streams? Do mechanical coatings removal media or residual
coatings come in contact with water streams? If so, do
concentrations of pollutants exceed limits established by the facility
NPDES permit or POTW discharge agreement?
D Does waste from equipment cleaning processes, particularly organic
solvent waste, contact waste water streams? If so, do concentrations
of pollutants exceed limits established by the facility NPDES
permit or POTW discharge agreement?
NOTES
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Chapter S'tx Self-Audit Preparation Guide
Section 3
Hazardous Materials/Waste Management
A. Records To Review
* Hazardous Substance Spill Control and Contingency Plan
* Spill records
* Emergency plan documents
* MSDSs
* Inventory records
* Hazardous substance release reports
* Shipping papers
* Training records
» Placarding of hazardous materials
* Hazardous Communication Plan
* Chemical Hygiene Plan (labs)
+ Notification (USEPA identification number)
* Hazardous waste manifests
4 Manifest exception reports
* Biennial reports
» Inspection Logs (as applicable)
* Delistings
» Land disposal restriction certifications
* Employee training documentation
* Contingency plan
B. Physical Features To Inspect
* Shipping and receiving area
* Hazardous material storage areas
* Hazardous material transfer areas
* Shop activities
* Hazardous waste generation sites
* Satellite accumulation points
* Accumulation points
* Vehicles used for transport
* Storage facilities (including drums)
* Treatment units
4 Recycling sites
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* Disposal sites
* Surface impoundments
C. Responsibilities of Supervisors and Managers
Supervisors and managers should...
D Establish Pollution Prevention Plans, in accordance with applicable
regulations. These plans must address hazardous materials (HM)
and hazardous wastes (HW) and encompass all aspects of health
and safety of personnel and protection of the environment
D Comply with applicable HW management requirements.
Compliance with all aspects of an EPA-approved state HW
management program is considered compliance with federal
requirements. If a state has a program that is not approved by EPA,
activities shall comply with both the state and federal program
requirements
D Eliminate HW disposal to the maximum possible extent by
eliminating the use of HM and by implementing best management
practices and best demonstrated available technology.
D Control and reduce the amounts of HM used and HW generated by
HM acquisition, supply, and utilization management
D Identify HM needed to meet production requirements and, where
feasible, substitute less hazardous material. Support decisions to
use hazardous material or substitute less hazardous material by an
economic analysis appropriate to the magnitude of the decision
being made
D Comply with all federal standards, directives, instructions, and
regulations related to hazardous materials and hazardous waste,
• including applicable state and local regulations
D Obtain and renew required operating permits for hazardous waste
facilities at all activities and complete construction of all required
hazardous waste storage and handling facilities
D Minimize land disposal of hazardous wastes.
D Develop and use a HW management plan, or HW component of a
Pollution Prevention Plan
D Budget, fund, and manage HW in compliance with applicable
substantive and procedural federal, state and local requirements
•D Cooperate with federal, state, and local HW regulatory officials
D Provide reports and other required data and information to federal,
state and local HW regulatory agencies
D Obtain and maintain applicable HW generator identification
number
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D Perform operations under applicable federal, state, and local
requirements
D. Supervisor's and Manager's Hazardous Materials/Waste
Management Checklist
Program Status
D Is our Hazardous Waste Management Plan current?
D Are our inventories of hazardous materials and wastes current?
D What is the status of our Hazardous Waste Minimization program?
D When does our hazardous waste disposal contract expire?
D Do our procedures for storage and dispensing of hazardous
materials and waste comply with applicable requirements?
D What are the cognizant regulatory agencies and who are our
contacts at these agencies?
D When was the most recent regulatory agency inspection of our
hazardous waste management facilities and what were the results?
D Do we have any RCRA corrective action projects programmed?
Hazardous Waste Management Facilities
D What types of hazardous waste management facilities do we have?
D What is their permit status?
D Do we have written operating procedures and operating logs for
each of our facilities?
D Are we conducting periodic inspections of our facilities?
D Have all of the operating personnel received appropriate training,
including required safety and health training?
D Do we have closure plans for all of our permitted facilities?
Accumulation Point Management
D How many hazardous waste accumulation points have been
designated? How many satellite accumulation points?
D Have accumulation point managers been appropriately trained?
D Are accumulation points inspected regularly to ensure that
hazardous wastes are segregated, properly labeled and stored for
less than 90 days from the start of accumulation?
NOTES
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Disposal Procedures
D Have we initiated procedures to ensure that hazardous wastes
shipped from this facility are properly packaged, labeled,
manifested, and transported? Do we ensure that we receive and file
all our hazardous waste manifests to verify completed disposal
actions?
D Do we have an inspection/certification plan for vehicles involved in
transporting hazardous waste?
RCRA Corrective Actions
D Do we have any sites for which corrective action is required under
RCRA? What is the status of the actions at these sites?
E. Organic Finishing Facility Checklist
D Are coating materials, chemical stripping solutions, and cleaning
solutions properly labeled and packaged in accordance with 40 CFR
Part 262, Subpart C?
D Are wastes contaminated with coating materials, organic solvents,
or chemical strippers classified as hazardous? If so, are the wastes
handled and manifested in accordance with 40 CFR Part 262,
Subpart B? Are hazardous wastes segregated from non-hazardous
wastes?
D Are dry wastes contaminated with residual coating from mechanical
and carbon dioxide blasting classified as hazardous? If so, are the
wastes handled and manifested in accordance with 40 CFR Part
262, Subpart B? Are hazardous wastes segregated from non-
hazardous wastes?
NOTES
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Chapter Six Self-Audit Preparation Guide
Section 4
Solid Waste Management
A. Records To Review
4 Record of current non-hazardous solid waste management practices
4 Estimated generation rates
4 Documentation of locations (map) and descriptions of all non-
hazardous waste storage, and disposal sites
4 Records of operational history of all active and inactive disposal
sites
4 State and Federal inspection reports
4 Environmental monitoring procedures or plans
4 Records of resource recovery practices, including the sale of
materials for the purpose of recycling
4 Solid waste removal contracts and inspection records
4 Regional solid waste management plan
4 Pollution prevention management plan
B. Physical Features To Inspect
4 Resource recovery facilities
4 Incineration and land disposal sites (active and inactive)
4 Areas where non-hazardous waste is disposed
4 Construction debris areas
4 Waste receptacles
4 Solid waste vehicle storage and washing areas
4 Transfer stations
4 Recycling centers
C. Responsibilities of Supervisors and Managers
Supervisors and managers should...
O Comply with all federal, state, and local requirements regarding
solid waste management and disposal
D Ensure an adequate solid waste disposal capability for all facility
activities
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D Identify economically recyclable wastes and identify markets for
these wastes which requires that scrap metal, high-grade paper,
corrugated containers and aluminum cans be segregated for
recycling
D Ensure that all activities have a Solid Waste Management Plan
(SWMP)
D Implement solid waste recycling and source reduction programs to
keep pace with national efforts to maximize recycling and recovery
of materials from solid waste
D Minimize the use of packaging materials in the supply system
D Develop SWMPs including source reduction and recycling
programs and resource recovery facilities that incorporate all
federal, state and local requirements
D Cooperate with the personnel/company that provides solid waste
collection and disposal services in establishing source reduction and
separation programs and affirmative procurement programs
D If listed in a Standard Metropolitan Statistical Area (SMSA),
cooperate with the designated SMSA lead agency
D. Supervisor's and Manager's Solid Waste Management and
Resource Recovery Checklist
Site Facilities
D What types of solid waste facilities are* operated by the facility?
D What is the status of the facility's Solid Waste Management Plan?
What is the permit status of these facilities?
D What monitoring and reporting is required for these facilities?
D What are our annual operating and disposal costs?
Use of Offsite Facilities
D Do we use any offsite solid waste disposal facilities?
h
D Have we verified that these facilities are appropriately licensed or
permitted and that they are in compliance with their permits?
D What are our annual disposal costs for offsite facilities?
Availability of Regional Facilities
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D Are there any regional solid waste management, recycling or
resource recovery programs? Is there a state or local household
hazardous waste program?
D Do we participate in these programs? If not, why?
Waste Minimization Programs
D Have we established a program to reduce the volume of solid waste
generated on the facility? If not, why?
D How successful has it been?
Recycling Programs
D Do we have a recycling program?
D Does the program encompass all personnel, including
manufacturing areas, office areas, etc.?
D How successful have they been?
Control of Hazardous Wastes
D What procedures are used to ensure that hazardous wastes are not
inadvertently (or intentionally) mixed with non-hazardous solid
wastes?
D How often are sources of both solid and hazardous wastes inspected
to ensure that hazardous wastes are not mixed with non-hazardous
solid wastes?
E. Organic Finishing Facility Checklist
D What process wastes, such as excess coating materials, have been
identified as solid wastes? Are these materials segregated from
hazardous materials?
D Are coating mateirals, rags, filters, coveralls, etc. collected and
disposed in an appropriate manner?
NOTES
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Section 5
Community Right-to-Know
A. Records to Review
4 Emergency Response Plans
4 Emergency and Hazardous Chemical Inventory Forms
4 Toxic Chemical Release Forms (EPA Form R)
4 Emergency plan documents
4 MSDSs
4 Inventory records
4 Hazardous substance release reports
4 Hazardous Communication Plan
4 Delistings
4 Contingency plan
B. Physical Features To Inspect
4 Shop activities
4 Hazardous material storage areas
4 Hazardous material transfer areas
4 Storage facilities (including drums)
4 Generation sites
Satellite accumulation points
Accumulations points
Treatment units
Recycling sites
Disposal sites
Surface impoundments
4
4
4
4
4
4
C. Responsibilities of Supervisors and Managers
Supervisors and managers should...
D Designate an employee to represent you on the local emergency
planning committee
D Account for the types and quantities of hazardous substances used
and stored at your facility
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D Notify the local emergency planning committees and state
emergency response commissions if you exceed a Threshold
Planning Quantities (TPQ) for an extremely hazardous substance
D Annually submit Emergency and Hazardous Chemical Inventory
Forms and Toxic Chemical Release Forms (EPA Form R) for all
chemicals exceeding prescribed thresholds to the appropriate
agencies
D Sign each EPCRA Form R as the validating official
D Prepare an activity plan to handle chemical emergencies similar to
the plan prepared by the local emergency planning committee
D Use data provided from EPCRA reporting to develop a
comprehensive Pollution Prevention Plan for the facility
D Reduce the releases of toxic chemicals as identified hi the Pollution
Prevention Plan to support a reduction in EPCRA reporting
requirements
D Identify funding needed to the major claimant to support all
EPCRA requirements
D Establish and implement procedures to control, track, and reduce
the variety and quantity of hazardous material in use, in storage or
stock, or disposed of as hazardous waste, to support reduced
EPCRA reporting.
D. Emergency Planning and Community Right-to-Know
Checklist
D Has a contact for local emergency response planning been
identified and does the community know who the individual is and
how to contact him or her?
D Does the facility participate in local, regional, or state emergency
response planning activities?
D Have facility response plans been developed and coordinated with
local authorities?
O Have procedures been developed for notifying state and local
emergency planning authorities in case a hazardous substance is
accidentally released that may harm facility personnel or off-facility
residents?
D If requested, can information concerning types and quantities of
hazardous substances used and stored on the facility be provided to
local authorities?
NOTES
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E. Organic Finishing Facility Checklist
D Are coating materials, chemical stripping solutions, and cleaning
solutions considered hazardous or extremely hazardous materials
and subject to reporting and recordkeeping requirements?
D Are MSDS available for all coating materials, stripping solutions,
cleaning solutions, etc.?
NOTES
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Section 6
Pollution Prevention
A. Responsibilities of Supervisors and Managers
Supervisors and managers should...
D Reduce the quantity of toxic pollutants disposed or transferred off
site through process modification, recycling, reuse, material
substitution or equivalent.
D Reduce the amount of hazardous material (HM) used and hazardous
waste (HW) generated by HM control in procurement, supply, and
use.
O Limit the use of hazardous materials. Establish methods of
substituting less hazardous materials or non-hazardous material.
D Develop and incorporate new technology or materials which have a
reduced impact on the environment, are safer and healthier for the
user, or result in reduced pollutant emissions.
D Incorporate pollution prevention into the design of new products
and modification to current products, support systems, and
facilities.
D Develop and implement a facility pollution prevention program that
incorporates the hazardous material control and management and
hazard communication requirements of the listed laws and
regulations.
D Implement and annually update the facility Pollution Prevention
Plan.
D Establish and implement procedures to control, track, and reduce
the variety and quantities of HM in use, in storage or stock, or
disposed of as HW.
D Develop and implement a facility level HM authorized use list
(AUL) using an inventory that identifies and quantifies HM,
including whether the material is an extremely hazardous substance,
hazardous substance, or toxic chemical as defined under EPCRA
D Ensure facility level supply functions establish and implement a
local shelf life control and management program.
NOTES
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B. Supervisor's and Manager's Pollution Prevention Checklist
D Do we have a Pollution Prevention (P2) Plan?
D Do we have an active P2 program? Has a P2 committee been
established?
D Have we established procedures to control, track, and reduce the
variety and quantities of HM in use, in storage or stock, or disposed
ofasHW?
D Do we have procedures for tracking toxic chemicals to assist with
EPCRA reporting?
D Do we have any challenging potential or actual pollution problems?
Are they addressed in our P2 Plan?
D What accomplishments in P2 have been attained to date?
D What are the ongoing programs to enhance P2 or recycling
awareness? Does the program involve all tenants?
D Do we invite or have any community involvement, activities, or
affiliations with civic or environmental organizations?
D Do we consider our relationship with federal, state, and local
agencies, organizations, and academic institutions to be excellent,
satisfactory, unsatisfactory, or hostile and why?
NOTES
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GLOSSARY
active solvent - A liquid which dissolves a
binder.
additives - Any substance added in small
quantities to another substance, usually to
improve properties. Examples of additives
include plasticizers, fungicides, and dryers.
air spray - A paint spray application system
using air at high velocity and pressure to
atomize the paint.
air-assisted airless spray - Paint spray
application system using fluid pressure to
atomize the paint and lower pressure air to
adjust the shape of the fan pattern.
air pollution control equipment - equipment
that removes particulates and/or volatile
organic compounds from exhaust air of
facilities.
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.
airless spray - Paint spray application system
using high fluid pressure to atomize paint by
forcing it through a small orifice.
aliphatic solvent - A solvent comprised
primarily of straight chain hydrocarbons,
including mineral spirits, kerosene, and
hexane. These solvents are characterized as
volatile organic compounds.
anode - The electrode at which chemical
oxidation takes place. In electrodeposition (E-
coating) the anode is indicated on diagrams by
the positive (+) marking.
applied coating solids - The. volume of dried
or cured coating solids which is deposited and
remains on the surface of the part.
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.
B
bake oven - A device that uses heat to dry or
cure coatings.
baked coatings - Coatings that are cured or
dried at or above an oven air temperature of
194 F (90 C).
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 or reciprocators.
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.
blistering - The formation of hollow bubbles
in the paint film caused by air, moisture, or
solvents trapped under the film.
CAA - Clean Air Act
carbon dioxide - CO2, is a non-toxic material
used in solid form to remove coatings. Carbon
dioxide is considered to be a "greenhouse gas"
which may contribute to global warming.
-------
cathode - The cathode is defined as the
electrode at which chemical reduction takes
place. In electrocoating, the cathode is
indicated on diagrams by the negative (-)
marking.
CD-ROM - Compact Disk-Read Only
Memory
CERCLA - Comprehensive Environmental
Response Compensation and Liability Act
CFC - Chlorofluorocarbons (CFCs) are
compounds made from combinations of
carbon, chlorine, and fluorine typically used
as propellants, cleaners, or cooling agents.
CFCs are non-toxic to workers, and are non-
flammable. The compounds are very stable in
the lower atmosphere and can persist for at
least 100 years. When the molecules reach
the upper atmosphere, they deplete the ozone
layer. Manufacturing of CFCs has been
banned in the US, and their use has been
extremely restricted.
CFR - Code of Federal Regulations
chipping - Total or partial removal of a dried
paint film in flakes by accidental damage or
wear during service.
chlorinated solvents - Powerful organic
solvents that contain chlorine. Examples
include 1,1,1-trichloroethane and methylene
chloride. These solvents are characterized as
volatile organic compounds.
coating - A liquid composition which is
converted to a solid protective, decorative, or
functional adherent film after application as a
thin layer.
conventional pollutants - Conventional
pollutants, as defined by the Clean Water Act,
include biochemical oxygen demand (BOD),
total suspended solids (TSS), fecal coliform,
oil, and grease, which have been present in
wastewater streams for many years.
cosolvents - Water-miscible organic solvents.
Waterborne paints frequently require
cosolvents in addition to water for easier
manufacture 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).
criteria pollutants - Under the National
Ambient Air Quality Standards (NAAQS)
regulations, the following compounds are
considered to be criteria pollutants:
particulate matter, nitrogen oxides, ozone,
sulfur dioxides, carbon monoxide, and lead.
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.
cure - Using heat, radiation, or reaction with
chemical additives to change the properties of
a polymeric system into a final more stable,
usable condition. For liquid coatings, it is the
process by which the liquid is converted into a
solid film.
CWA - Clean Water Act
D
deionized water - Water resulting from the
removal of contaminants in the water by a
double-bed ion exchanger. Deionized water is
equivalent 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 rather are
used to control viscosity, flash time, or cost.
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.
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dip coating - The process in which a substrate
is immersed in a solution (or dispersion)
containing the coating material and
withdrawn.
disks (discs) - Rotating heads that deliver
paint horizontally 360 degrees around the
head and use an omega loop conveyer line. A
disk is usually mounted horizontally on a
vertical reciprocator.
E
Effluent Guidelines and Standards -
Effluent guidelines and standards are the basis
for controlling the discharge of pollutants,
primarily in wastewater, from industrial
facilities and publicly owned treatment works
(POTWs) to lakes, streams, and other
receiving waters, as well as from industrial
facilities to POTWs. The EPA developed the
industry-specific, technology-based standards
to cover facilities performing similar
operations which would use similar processes
for pretreatment. Individual states developed
additional standards which would protect
water quality in their regions.
electrocoating - A dip coating application
method where the paint solids are given an
electrical charge which is then attracted to the
part. In a method closely paralleling
electroplating, paint is deposited using direct
electrical current. The electrochemical
reactions that occur cause water-soluble resins
to become insolubilized onto parts that are
electrodes in the E-coating paint tank.
Subsequent resin curing is required.
electrostatic spray - Methods 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 a latex, which consists of
solids dispersed in a liquid.
. EPA - United
Protection Agency
States Environmental
EPCRA - Emergency Planning
Community Right-to-know Act
and
film - One or more layers of coating covering
an object or surface.
flash-off area - The portion of a surface
coating operation between the coating
application area and bake oven.
flash point - The lowest temperature of a
liquid at which it gives off sufficient vapor to
form an ignitable mixture when mixed with air
and brought in contact with an open flame or
spark.
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 a porous plate bottom of a powder
hopper. This permits the fluidized bed of
powder particles to be used in dip tanks and to
be transported in a manner similar to liquids.
G
ground (electrical ground) - An object so
massive that it can lose or gain
overwhelmingly large numbers of electrons
without becoming perceptibly charged.
H
halogenated solvents - Formed by
substituting one of the halogen elements
(chlorine, bromine, or fluorine) into a
chemical compound to change both the
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physical and chemical natures of the
compound.
Hazardous Air Pollutants - Hazardous air
pollutants (HAP), also referred to as "air
toxics," pose a significant threat to human
health and the environment. Common HAPs
include benzene, toluene, formaldehyde,
mercury, and polyaromatic hydrocarbons.
They are emitted from a wide variety of
sources, such as combustion sources and
compounds found in organic solvents. EPA
originally listed 189 HAPs and continues to
establish National Emission Standards for
Hazardous Air Pollutants (NESHAP) for
various industrial sources.
HAP - Hazardous Air Pollutant
HCFC - Hydrochlorofluorocarbons (HCFC)
are compounds made from carbon, chlorine,
fluorine, and hydrogen commonly used as
replacements for chlorofluorocarbons (CFC).
While the compounds provide similar
propellant, cleaning, and cooling capabilities
as CFCs, they are slightly less damaging to the
ozone layer.
heavy metals - Heavy metals include
mercury, lead, cadmium, and zinc. These
materials may be found in some coating
material formulations, surface preparation
solutions, or as part of substrates.
Concentrations of these materials are limited
in wastewater by the National Pollutant
Discharge Emissions Standards. The metals
may enter wastewater discharges as a result of
ph'osphatizing rinses or from wet blasting of
coatings materials.
High-volume low-pressure spray - Spray
equipment used to apply coating by means of
a gun which operates between 0.1 and 10.0 psi
air pressure. The high volume of air is
produced by a turbine.
high-solids - Solvent-based coatings that
contain greater than 50 percent solids by
volume or greater than 62 percent(69 percent
for baked coatings) solids by weight.
HVLP - High-volume, Low-pressure
hydrocarbon solvent - An organic compound
consisting exclusively of the elements carbon
and hydrogen. They are principally derived
from petroleum and coal tar, and include
aliphatic, aromatic, and napthenic solvent.
Infrared (IR) - Wavelengths of light energy
that produce thermal energy, used to heat
coatings and substrates to cure coating
materials.
listed and characteristic hazardous wastes -
Characteristic hazardous wastes are materials
that exhibit toxicity, reactivity, ignitability,
and/or corrosivity. Materials with these
characteristics have been found to cause or
contribute to an increase in mortality or
serious illness, or pose a hazard to human
health or the environment when improperly
treated, stored, transported, disposed or
otherwise managed. Listed hazardous wastes
are materials specifically identified as
hazardous because they have exhibited
characteristics of hazardous wastes, have been
found to be fatal to humans or to test animals,
or contain toxic, carcinogenic, mutagenic, or
teratogenic constituents. Both individual
materials and categories of materials are listed
as hazardous.
M
Material Safety Data Sheets - Material
Safety Data Sheets (MSDS) are informational
fact sheets developed for each commercially
available chemical, compound, or substance.
MSDSs provide general product information,
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physical components and characteristics of the
product, .health risk information, fire and
explosion warnings, product reactivity data,
spill and disposal procedures, storage and
handling issues, and personal protective
equipment suggested when working with the
material. MSDSs are to be made easily
accessible to employees working with
chemical substances and to surrounding
communities.
MEC - Methylene chloride
MEK - Methyl ethyl ketone
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 in
the molten salt bath.
MSDS - Material Safety Data Sheet
N
National Ambient Air Quality Standards
(NAAQS) - National Ambient Air Quality
Standards (NAAQS) establish maximum
concentrations for criteria air pollutants in
specified geographical areas. These pollutants
include carbon monoxide (CO), lead (Pb),
nitrogen dioxide (NO2), paniculate matter
(PM-10), ozone (O3), and sulfur dioxide
(SO2). To prevent established concentrations
from being exceeded, State and local
governments may require air pollution
controls on existing, new, and modified
industrial facilities; tighter standards on
emissions from motor vehicles; and the use of
alternative fuels.
National Emission Standards for
Hazardous Air Pollutants (NESHAP) -
National Emission Standards for Hazardous
Air Pollutants (NESHAP) establish limits on
emissions of hazardous air pollutants.
National Pollutant Discharge Elimination
System (NPDES) Permits - National
Pollutant Discharge Elimination System
(NPDES) Permits limit discharges of
pollutants into water from point sources.
Industrial dischargers must obtain permits
prior to releasing wastewater into receiving
waters.
nitrous oxides NOx - NOx are emissions of
nitrogen oxides typically created during the
combustion of fuels during dry-off and curing
stages of organic finishing.
non-conventional pollutants - Non-
conventional pollutants under the Clean Water
Act are defined as any pollutants not
classified as either toxic or conventional
pollutants. EPA included this classification to
account for developments in industry and the
changing characterization of possible water
pollutants.
o
omega loop - The conveyor for rotating disk
paint applicators that is shaped to produce a
circular path around the vertically oriented
disk to deliver paint from all 360 degrees of
its circumference. The term was derived
because the shape of the conveyor resembles
the capitalized form of the Greek letter.
organic coating - A coating used in a surface
coating operation, including dilution solvents,
from which volatile organic compound
emissions occur during the application or the
curing process. For the purpose of many
.environmental regulations, powder coatings
are not included in this definition.
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 the properties of the
coating.
overspray - Any portion of a spray-applied
coating which does not land on a part and
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which is deposited on the surrounding
surfaces.
ozone-depleting substances - Ozone-
depleting substances (ODSs) are chemical
compounds that harmfully react with ozone to
transform ozone into oxygen. The most
common ODSs are chlorofluorocarbons
(CFCs). These compounds transform ozone
into oxygen while continuously recycling
chlorine within the atmosphere. The constant
supply of chlorine in the atmosphere supports
additional ozone depleting reactions.
particulate matter - Particulate matter (PM)
is the term used for a mixture of solid particles
and liquid droplets found in the air. While
individual particles can not be seen with the
naked eye, collectively they can appear as
black soot, dust clouds, or gray hazes.
Particles originate from a variety of sources in
organic coating facilities, most often exhaust
from drying ovens.
permeate - The output of ultrafiltration,
called ultrafiltrate or permeate.
pH - Value taken to represent the acidity or
alkalinity of an aqueous solution and defined
as the logarithm of the reciprocal of the
hydrogen-ion concentration of a solution. The
scale ranges from 1 for highly acidic solutions
to 13 for highly basic or alkaline solutions.
neutral solutions have a pH of 7. Because the
scale is logarithmic, the intervals are
exponential.
phosphating - A pretreatment for steel or
certain other metal surfaces by chemical
solutions containing metal phosphates and
phosphoric acid as the main ingredients, to
form a thin inert adherent, corrosion-
inhibiting phosphate layer 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 also
inorganic or organic.
point source pollutants - Point source
pollutants are direct wastewater discharges
into national water sources, such as rivers,
lakes, and streams. Common discharge
sources of point source pollutants are pipes,
ditches, channels, and sewer deposits.
polymers - A high molecular weight organic
compound, natural or synthetic, with a
structure that can be represented by a repeated
small unit, or mer.
pot life - The length of time a coating material
is useful after the original package is opened
or after a catalyst or other ingredient is added.
POTW - Publicly Owned Treatment Works
powder coatings - Any coating applied as a
dry (without solvent or other carrier), finely
divided solid that adheres to the substrate as a
continuous film when melted and fused.
Pretreatment - Pretreatment of wastewater
removes oils, dirt, solids, hazardous liquids
and adjusts pH before the waste stream is
discharged. Pretreatment standards must be
met prior to discharge to a publicly owned
treatment works (POTWs). Pretreatment
requirements are imposed by the POTW upon
industrial dischargers to protect POTW
equipment and personnel, and to ensure that
water leaving the POTW has received
adequate treatment.
primers - Coatings that are designed for
application to a surface to provide a firm bond
between the substrate and subsequent
coatings.
priority pollutants - Priority pollutants are
hazardous or radioactive organic and
inorganic chemicals present in an
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environmental setting, such as air, water, or
vegetation. These pollutants were identified
by EPA as indicators of environmental
contamination.
publicly owned treatment works (POTWs)
- Publicly Owned Treatment Works (POTWs)
are treatment works owned by a State, unit of
local government, or Indian tribe, usually
designed to treat domestic wastewaters.
POTWs are required to demonstrate that
industrial sources of toxic pollutants are in
compliance with all of their pretreatment
requirements, including local limits.
R
RCRA - Resource Conservation and
Recovery Act
rebound - Paint droplets from air-atomized
application that rebound or bounce away from
the surface due to the blasting effect of the air.
receiving water - any water source into
which effluent may be discharged, such as
lakes, ponds, oceans, and rivers. Receiving
waters must support a balanced population of
fish and wildlife, allow for recreation, and
show need for protection to maintain these
uses.
reciprocator - An automatic device to move 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.
roll coating - Process by which a film is
applied mechanically to sheet or strip
material.
sagging - The downward flow of a coating
film as a result of the film being applied too
heavy or too fluid a wet coat.
solvent - The liquid or blend of liquids used to
dissolve or disperse the film forming particles
and which evaporate during drying. A true
solvent is a single liquid that can dissolve the
coating. Solvent is often used to describe
terpenes, hydrocarbons, oxygenated, furans,
nitroparaffiins, and chlorinated solvents.
solvent-based - Coatings in which volatile
organic compounds are the major solvent or
dispersant.
spray application - A method of applying
coatings by atomizing and directing the
atomized spray toward the part to be coated.
spray booth - A structure housing automatic
or manual spray application equipment where
coating is applied to parts. Dry filters or
waterwashes are used to remove particulates
from the exhaust air.
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 one object to another if at all
possible in order to neutralize all charges.
suspended solids - Suspended solids are small
particles of solid pollutants that float on the
surface of, or are suspended in, sewage or
other liquids. They resist removal by
conventional means, and therefore require
specially designed instruments for removal.
terpene solvents - Volatile organic
compounds obtained from pine tress and are
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the oldest solvents used in coatings, includes
turpentine, dipentene, and pine oil.
thermoplastic - Resin capable of being
repeatedly softened by heat and hardened by
cooling. These materials, when heated,
undergo a substantially physical rather than
chemical change. Thermoplastic resins can be
completely dissolved with appropriate
solvents.
thermoset - Resin that, when cured by
application of heat or chemical means,
changes into a substantially infusible and
insoluble material. Thermosetting resins will
soften but will not dissolve in any solvents.
thinning - The process of adding volatile
liquid to a coating to reduce its viscosity. This
liquid may be solvent, diluent or mixtures of
both. Also may be called reducing or "adding
make-up solvent".
Title V permitting - Title V permitting is the
mechanism by which EPA integrates all of the
federally applicable requirements of the Clean
Air Act designed to reduce emissions of air
toxics, improve and maintain air quality, meet
new source requirements, and control the
precursors of acid rain. The operating permit
program is administered by states under
federally approved programs. A facility's
operating permit will indicate the emissions
standards and operation limitations that it
must follow in order to stay in compliance.
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.
toxic organics - Toxic organic chemicals
include a variety of chemicals, such as
polychlorinated biphenyls (PCB) and dioxin,
that are considered to be severely damaging to
human health, wildlife, and aquatic species.
The toxic organics are persistent in the
environment, remaining chemically reactive
for long periods. The materials can
accumulate in animal and fish tissue, be
absorbed in sediments, or find their way into
drinking water supplies, posing long-term
health risks to humans.
toxic pollutants - Toxic pollutants are those
priority pollutants identified by EPA that
display toxic, hazardous characteristics.
Toxic Release Inventory - The Toxic Release
Inventory (TRI) is a compilation of chemical
procurement and release data from
manufacturing facilities in the US TRI reports
are required for facilities with more than 10
full-time equivalent employees and that use
more than 1,000 pounds of a listed substance
annually. Facilities are required to report
hazardous, toxic, and ozone-depleting
chemicals used, and the amount of each
released to the air, publicly owned treatment
works, receiving waters, landfills, and other
disposal facilities. EPA maintains a database
of records for public record.
transfer efficiency - The ratio of solids
adhering to an object to the total amount of
coating solids used in the application process,
expressed as a percentage. Non-adhering
paint, or overspray, goes onto booth surfaces,
hooks, filters, etc.
u
ultrafiltration - Ultrafiltration uses low-
pressure membrane filtration to separate small
molecules from large molecules and fine
particulates. For example, electrocoat rinse
water is extracted from the paint bath by
ultrafiltration.
UV - Ultraviolet
underbake 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
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tackiness, softness, and inferior film
durability.
varnish - Clear or pigmented coatings
formulated with various resins and designed to
dry by chemical 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.
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.
VOC - Volatile Organic Compound
VOC content - The proportion of a coating
that is volatile organic compounds (VOCs),
expressed as kilograms of VOCs per liter of
coating solids. In calculating the VOC content
of the coating, exempt compounds and water
are excluded and are not considered to be part
of the coating. Exempt compounds are
acetone, ethane, methane, carbon monoxide,
carbon dioxide, carbonic acid, metallic
carbides, metallic carbonates, ammonium
carbonate, methylene chloride, 1,1,1
trichloroethane (methyl chloroform), 1,1,2
trichlorolotrifluoroethane (CFC-113),
trichlorofluoromethane (CFC-11),
dichlorodifluoromethane (CFC-12),
dichlorotetrafluoroethane (CFC-114),
chloropentafluoroethane (CFC-115),
trifluoromethane (CFC-23), and
chlorodifluoromethane (CFC-22). Many of
these exempt compounds may contribute to
upper atmosphere ozone destruction.
VOC emissions - The mass of volatile
organic compounds (VOCs), expressed" as
kilograms of VOCs per liter of applied coating
solids, emitted from a surface coating
operation.
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.
volatility - The tendency of a liquid to
evaporate. Liquids with high boiling points
have low volatility and vice versa.
voltage - A measure of the potential
difference (force or pressure) in electrical
systems.
w
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).
wrap around - Electrostatic effect where
charged coating particles curve around the
part and are deposited onto the rear side of the
part.
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REFERENCES
Metal Finishing magazine is a technical periodical published monthly featuring articles on organic
and inorganic metal finishing materials, technologies, and developments. Elsevier Science
Publishers.
Products Finishing magazine is a technical periodical published monthly featuring articles on
inorganic and organic metal finishing materials, technologies, and developments.
Coating Alternatives Guide (cage.rti.org) and Solvent Alternatives Guide (clean.rti.org). The
Coating Alternatives Guide (CAGE) and the Solvent Alternatives Guide (SAGE) are
pollution prevention tools utilizing an expert system and information base designed to
recommend low-emitting alternative coating or cleaning technologies. The tools were
developed by the Pollution Prevention Program and the Surface Cleaning Program at
Research Triangle Institute in cooperation with the U.S. EPA Air Pollution Prevention and
Control Division.
Metal Finishing: Organic Finishing Guidebook and Directory. New York: Elsevier Science
Publishers. 1997.
Ohio Environmental Protection Agency. Pollution Prevention in Painting and Coating Operations
Fact Sheet Number 23. Ohio EPA, Columbus, Ohio. September 1994.
Products Finishing: Directory and Technology Guide. Cincinnati, Ohio: Gardner Publications.
1997.
United States Environmental Protection Agency. Fundamentals of Environmental Compliance
Inspections. Government Institutes, Inc., Rockville, Maryland. August 1989.
United States Environmental Protection Agency, Guide to Cleaner Technologies: Organic Coating
Replacements. U.S. EPA, Washington, DC. EPA/625/R-94/006. September'1994.
United States Environmental Protection Agency. Guides to Pollution Prevention: The Fabricated
Metal Products Industry. U.S. EPA, Washington, DC. EPA/625/7-90/006. July 1990.
United States Environmental Protection Agency. Manual: Pollution Prevention in the Paints and
Coatings Industry. U.S. EPA, Washington, DC. EPA/625/R-96/003. September 1996.
United States Environmental Protection Agency. Profile of the Fabricated Metal Products Industry.
U.S. EPA, Washington, DC. EPA 310-R-95-007. September 1995.
United States Environmental Protection Agency. Report: Compliance Coatings for the
Miscellaneous Metal Parts Industry. U.S. EPA, Washington, DC. EPA 340/1-91-009.
August 1991.
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