PB81-226268
VOC Emission Control Technologies for Ship
Painting Facilities: Industry Characterization
CENTEC Corp.
Reston, VA
Prepared for
Environmental Protection Agency
Cincinnati, OH
Jul 81
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PB81-226268
EPA-600/2-81-131
July 19C1
VOC EMISSION CONTROL TECHNOLOGIES
FOR SKIP PAINTING FACILITIES
- Industry Characterization -
Prepared by
CENTEC Corporation
11260 Roger Bacon Drive
Reston, VA 22090
Project Officer
Charles H. Darvin
Nonferrous Metals and Minerals Branch
Industrial Environmental Research Laboratory
Cincinnati, OH 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH ANU DEVELOPMENT
THE UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
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TECHNICS. flEPORT DATA
(llcasr read luunicliun' •«'! the rneru lu-jurc t u
EP4-60y/2-81-131
ORD Report
7I7.E AVOSUOTITI E
VOC Emission Control Technologies for Ship Painting
Facilities
7 AUTHOR Si
J. W. Meredith, M. Moskowitz, J. G. Kresky
D. Harrison
a
8
3 RECIPIFNf S AC
m
"REPOHT DATE
July 1931
C PERFORMING ORGANIZA1 ION COOfc
9 PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION' NAME AND ADOflCSS
CENTEC Corporation
11260 Roger Bacon Dr.
Reston, VA 22090
10 PROGRAM fcLEVtNTNO
1AB604
11 CONTRACT/GRANT NO
WE-2907-10
12 SPONSORING AGEr.CV NAME AND ADDRfSS
Industrial Environmental Research Laboratory
Cincinnati, OH
Office of Research & Development
U. S. Environmental Protection Agency
13 TVPE OF PCPGRT AND PE3IOO CC i/EREO
Mar. 1980 - Feb. 19S1 F
U. SPONSORING ACENCV CODE
nPA6fiO/12
4S268
Viie U. S. Environmental Protection has the responsibility of reducing tne levels
of VOC emissions from the natio.i's stationary and mobile sources. The project was
directed at assessing the levels of VOC emissions from ship painting operations v.ith
the intent of determining the need for research activity in this industry. A
secondary objective was to identify control technologies or new technology concepts
which may be used or developed and demonstrated that lowers the levels of VOC
er.issicns during ship painting. Tne investigators reviewed the literature and Mode
direct contact with the ship building and repairing industry to develop their
conclusions and recommendations on technology concepts.
On a combined basis the 76 largest shipyards in the U.S. were round to Currc -ly
emu 41 to 95 metric Tons (45 to 105 short tons) of VOC into the atmosphere each
operating day. Military painting account for approximately 50 percent of that vc.ure
The technology approach for potentially reducing the VOC emissions levels are paint
reformulation and increase transfer efficiency of the painting equipment. |
KEY WORDS AMU DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution Control
Metal Finishing
Volatile Organic Compounds
h.lDENTIHLSS/OPEN' EMOED TERMS
n-:
COCA- I ic!i!>'.:nu
Metal Coating
Painting
VOC Emissions
I
19 SECURITY CLASS ITI.is Kepori/ ill NO. C'i>AG'a
Release to Public
!2 PRICE
EPA Form
(9-71J
62
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DISCLAIMER
This report has been reviewed by the Industrial Environmental
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publicatio- . Approval does not signify that the
contents necessarily reject the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
ii
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FOREWORD
When energy and material resources arc extracted, processed, converted,
and used, the pollution related impacts en our environment and even on our
health often require that new and increasingly more efficient pollution
control methods be used. The Industrial Environmental Research Laboratory -
Cincinnati assists in developing and demonstrating new and improved method-
ologies that will meet these needs both efficiently and economically.
This report presents the results of an investigation into the control of
solvent (VOC) air oollutant emissions from ship painting operations. The
study was performed to quantify the volume of VOC released to the atmosphere
from ship painting processes and to identify potential control concepts or
allow more effective control of the VOC emissions. The results are being
used within the Agency's Office of Research and Development as part of a
larger effort to develop improved technologies for reducing pollutant dis-
charges in the metal finishing and fabrication industries. The findings
will also be useful to other Agency components and industry in dealing with
environmental control problens. The Ncnferrous Metals and Minerals Branch
of the Energy Pollution Control Division should be contacted for any addi-
tional information concerning this program.
David G. Stephan
Director
Industrial Environmental Research Laboratory
Cincinnati
111
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A3STRAC"1
This project was initiated to identify control technologies
available or having potential for reducing the quantities of
volatile organic compounds (VCC) emitted from ship paintinq
operations. A second goal was to estimate the amount of VOC
being emitted on a daily basis for the entire indur-iry.
VOC emission control can be attained by any of three approaches:
1) Change paint formulations by either reducing or
eliminating solvents, or create paints that last longer
and therefore reduce the number of times a ship is
painted with attendant VOC releases.
2) Improve the transfer efficiency by modifying paint
application technologies.
3) Install add-on equipment that captures and destroys or
reclaims the VOC.
The first two approaches are being actively pursued by the ship
painting industry, primarily because of the economic benefits
associated with them and not as part of a VOC reduction goal.
The third approach (add-on equipment) has two major problems:
the first is the nature of the operation which makes capture
systems impractical and the second is the high cost.
There is no known use or consideration for use of add-on
control equipment in this industry. Therefore further reduc-
tions in VOC emissions from ship painting will come from
increased use of low solvent and/or high performance paints
and/or increased transfer efficiencies. It appears that the
development of higher performance paints will continue.
On a combined basis the 76 largest shipyards in the U.S. are
currently emitting 27.9 to 65.3 metric tons (31 to 72 short
tons) of VOC into the atmosphere 0:1 a daily basis (365 days/yr).
Military ship painting accounts for about 50 percent of this
amount.
This report was submitted in fulfillment of Contract No. WE-
2907-10 between the U.S. Environmental Protection Agency and
CENTEC Corporation, Reston, Virginia. This report covers the
iv
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period July 14, 1980 to April 14, 1981 and work was completed
as of April 14, 1981.
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CONTENTS
Section Title
ABSTRACT iii
FIGURES Viii
TABLES ix
ACKNOWLEDGEMENTS x
SECTION 1
INTRODUCTION 1
SECTION 2
CONCLUSIONS 2
SECTION 3
RECOMMENDATIONS 5
SECTION 4
SHIPYARD PRACTICES
RELATED TO PAINTING
4.1 INDUSTRY DESCRIPTION 6
4.2 GENERAL PAINTING PRACTICES 7
4.3 GEOGRAPHICAL DISTRIBUTION 8
4.4 FREQUENCY OF PAINTING 9
4.5 QUANTITIES OF PAINT USED 11
4.6 TURN-AROUND TINE 12
vi
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CONTENTS
(Continued)
Section Title Page
SECTION 5
MARINE PAINTS
5.1 MAJOR PAINTS FOR MARINE APPLICATIONS ... 13
5.1.1 GENERAL 13
5.1.2 ACRYLIC RESINS 14
5.1.3 ALKYD RESINS 17
5.1.4 EPOXY RESINS 18
5.1.5 POLYURE7HANES 20
5.1.6 VINYL RESINS 22
5.1.7 CHLORINATED RUBBER 26
5.1.8 INORGANIC ZINC COATINGS 26
5.1.9 ANTIFOUL1NG COATINGS 27
5.2 THE ROLE OF VOC IN PAINT 28
5.3 WATERBORNE PAINTS 33
5.4 TRENDS IN INDUSTRY 35
5.4.1 THE USE OF TWO-PART REACTIVE PAINTS .... 35
5.4.2 THE USE OF WATERBORNES 36
5.4.3 MARINE PAINTING RESEARCH 37
SECTION 6
VOC EMISSION CONTROL TECHNOLOGIES
6.1 INTRODUCTION 39
6.2 MODIFICATION OF PAINT FORMULATIONS .... 39
6.3 CAPTURE TECHNOLOGIES 41
vn
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TABLE OF CONTENTS
(Continued)
Section Title Page
6.4 EMISSION REDUCTIONS BY IMPROVING APPLICATION
TECHNOLOGIES 42
6.4.1 OPTIONS FOR APPLYING PAINTS 42
6.4.2 SPRAY PAINTING TECHNOLOGIES 43
6.4.3 NEW TECHNOLOGY 47
SECTION 7
ESTIMATION OF NATIONAL
VOC EMISSIONS FROM MAJOR
SHIPYARD PAINTING SO
BIBLIOGRAPHY 56
GLOSSARY 58
viii
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LIST OP FIGURES
Figure Title Page
6-1 Paint Spraying Systems 44
IX
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LIST OF TABLES
Number Title Page
4-1 Inventory of Major U.S. Shipyards 6
4-2 Inventory of Facilities at Major U.S.
Shipyards 7
4-3 Concentrations of U.S. Shipyards 8
5-1 Comparison of Resin Systems 15
5-2 Areas of Application for Ship Paints ... 16
5-3 Description of Organic Solvents Used in
Marine Paints 29
5-4 Common Paint-Solvent Systems for Marine
Applications 33
5-5 Percent Solids by Type of Paint 33
5-6 Two-Part Reactive Paint as Percent of Total
Paint Use 36
5-7 Waterborne Paint as Percent of Total Paint
Use 37
6-1 Solvent Proportions by Type of Paint ... «0
7-1 Paint Use and Employment at Shipyards
Visited 51
7-2 Estimated VOC Emissions from Painting at
Major Shipyards 53
7-3 Summary of VOC Emission Estimates 55
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ACKNOWLEDGMENTS
The authors would like to thank George S. Thompson, Jr., Branch
Chief, and Charles H. Darvin, Project Officer, Nonferrous Metals
and Minerals Branch, Industrial Environmental Research Labora-
tory, Cincinnati, Ohio for their direction and assistance
during this project. Acknowledgment is also due Edward Vincent
of EPA's Office of Air Quality Planning and Standards for his
direction and review of the project. A special thank you goes
to the Environmental Committee of the Shipbuilders Council of
America chaired by Georce Curtis III for invaluahle assistance
in providing data, arranging for site visits, and reviewing the
draft report.
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SECTION 1
INTRODUCTION
The primary objective of this study was to identify technologies
that serve to reduce volatile organic compound (VOC) emissions
from ship painting operations and to perform a preliminary
evaluation of these technologies. Another objective was to
define the sources and characteristics of ths VOC emissions. As
this investigation was primarily interested in the painting of
very large structures, only shipyards with facilities for
vessels 91.4 meters long (300 feet) and 1814 metric tons (2000
short tons) or over were considered.
Conversations with relevant trade associations led to contacts
with individual paint formulators, painting equipment manufac-
turers* and shipyards. Based on these contacts, site visits,
and the literature, an understanding of the industry and its
flexibility and constraints with regard to VOC emission control
was developed. The site visits accomplished constitute a
national sample of shipyards from the defined population.
Information obtained during these visits has allowed a statis-
tical determination of total nationwide VOC emissions from
major shipyards.
To aid the reader in understanding the industry, this report
includes a section on general shipyard operating procedures with
regard to ship painting. As the source of the VOC emissions is
the paint, a detailed section on marine paints is included.
Common control technologies are evaluated as to their relevancy
to ship painting and some innovative technologies are described
in detail. In all sections, industry trends observed are noted.
The report concludes with a section in which VOC emissions from
ship paint operations nationwide are estimated.
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SECTION 2
CONCLUSIONS
Approximately 63.5 metric tons (70 short tons) of volatile
organic compounds (VOC) are being emitted daily from the 76
largest shipyards in this country. The source of the VOC is
the organic solvents present in the paint formulations and
also solvents used for thinning paint and cleaning painting
equipment.
Marine coatings are absolutely vital for protecting the ships
from corrosive and biotic attacks from the snip's environment.
There are many marine paints serving specific functions such as
corrosion protection, abrasive protection, and antifouling.
Numerous types of paints can serve the same functions and each
may use different solvents at various volume percents. Ship
owners and paint formulators specify the paints and coating
thicknesses to be used at shipyards.
The major U.S. shipyards are scatterd along the east, west, and
Gulf coasts with a few inland waterway sites and island loca-
tions. Yards designed primarily for repair consume considerably
more paint and therefore generate more VOC emissions than yards
that do primarily construction of new ships. Specific paint
selections are based on the intended use of the ship, ship
activity, travel routes, desired time between paintings, the
aesthetic desires of the ship owners, and fuel costs.
VOC emission control can be attained by any ofpthree approaches:
1) Change paint formulations by either reducing or elimi-
nating solvents or create paints that last longer and
therefore reduce the number of times a ship is painted
with attendant VOC releases.
2) Improve the transfer efficiency by modifying paint
application technologies.
3) Install add-on equipment that captures and destroys or
reclaims the VOC.
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The first two approaches arc being actively pursued by the ship
parnting industry, primarily because of the economic benefits
associated with them and not as part of a VOC reduction goal.
The third approach (add-on equipment) has two major problems:
the first is the nature of the operation which makes capture
systems impractical and the second is the high cost.
Although high performance coatings will always cost more initi-
ally, their life-cycle costs may be significantly better than
that of conventional coatings. As a visit to a drydock can cost
more than $100,000 per day, ship owners want to minimize the
frequency of these visits, and continuous development of tech-
nologies that can help achieve this desire is likely.
The consensus of the environmental committee of the Shipbuilders
Council of America is that while the painting of 'J.S. Navy ships
accounts for approximately 30 percent of marine paint consump-
tion it is likely to be responsible for 50 percent of the VOC
being emitted. The reason for this is that the military speci-
fications for paints have not kept up with the state-of-the-art
and require extensive use of high solvent paints.
An analysis of the data collected during this study allows
the following specific conclusions to be made:
1) The nature of ship painting necessitates extensive use
of the most inefficient paint application technique—
spray painting.
2) There is a definite trend toward higher utilization of
airless paint spraying as opposed to air spraying. This
is due to airless spraying's higher transfer efficiency,
ability to spray higher solids paint, and ability to
spray a thicker coat per pass.
3) Conventional control technologies, such as capture
and destroy systems, are not applicable to shipyards for
major technical and economic reasons.
4) U.S. shipyards painting large ships on a combined basis
are currently emitting between 40.8 and 95.3 metric tons
(45 and 105 short tons) of VOC per day (250 days per
year). This is equivalent to a range of 27.9 to 65.3
metric tons (31 to 72 short tons) based on 365 days
per year which is more realistic for many shipyards.
Military ship painting accounts for about 50 percent of
the VOC being emitted.
5) Costs are forcing the industry to reduce VOC emissions.
This conclusion is illustrated by trends in industry
toward the use of high solids and high performance
paints, and paint application techniques with higher
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transfer efficiencies. These trends reduce VOC emis-
sions as a welcome but not intentional .side benefit in
most cases.
6) There is no known use or consideration for use of
add-on control equipment in this industry. Therefore
further reductions in VCC emissions from ship painting
will come from increased use of low solvent and/or high
performance paints and/or increased transfer efficien-
cies. It appears that the development of higher per-
formance paints will continue.
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SECTION 3
RECOMMENDATIONS
In order that shipyards may make decisions related to ship
painting based on sound empirical data rather than estimates,
it is recommended that the EPA conduct studies investigating
the true transfer efficiencies ot the various coating applica-
tion technologies. It is anticipated that this type of data
would allow quantification of paint losses and therefore provide
an economic basis upon which shipyards can make decisions. This
would accelerate the trend toward more efficient technologies
with thsir attendant lower VOC emissions. The Docknight" paint-
ing system described in this report is specifically recommended
for a transfer efficiency type of evaluation as it has direct
application to ship painting operations.
It is further recorr.;,.ended that EPA publish a report or both
high solids and high performance coatings that are useable
by the ship painting industry. The report should highlight
benefits, dispel myths, and encourage the use of these coatings
in lieu of coatings which either have higher VOC content or
require more frequent paint applications.
The large relatively flat surfaces on a ship's hull would be
likely candidates for roller coating if the proper technology
could be developed. Roller coating has a nearly 100 percent
transfer efficiency and would likely result in reduced VOC
emissions. It is recommended that a research and development
program investigate the design and feasibility of a mechanical
roll coating system suitable for painting the hulls of ships.
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SECTION 4
SHIPYARD PRACTICES RELATED TO PAIN1ING
4.1 INDUSTRY DESCRIPTION
Q
The Maritime Administration lists 76 U.S. shipyards that
qualify as Code A shipyards, meaning that they have facilities
capable of handling vessels 91.4 rceters long (300 feet) ur
longer and weighing 1814 metric tons (2,000 short tons) or more.
As the focus of this study is on the VOC emissions associated
with the painting of large ships, it is these 76 yards and their
painting practices that provided most of the data for this
report. These shipyards can be divided into three categories
based on their capabilities as follows:
1) Construction facilities only
2) Repair facilities with construction capabilities, or
3) Repair facilities only
The national inventory of these large shipyards (those having
facilities to either build or drydock ships of over 91.4 meters
(300 feet) in length or over 1814 metric tons (2,000 short tons)
by category is shown in Table 4-1.
Table 4-1
Inventory of rtajor U.S. Shipyards
Shipyards without repair capabilities 3
Combination of construction
and repair facilities 47
Repair facilities without construction capabilities 26
The actual type of facilities for doing the building or repair
work at these yards is listed in Table 4-2.
Superscripts refer to items in the Bibliography, p. 56.
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Table 4-2
Inventory of Facilities at Ma]or U.S. Shipyards
Building positions on land 83
Graving docks 79
Floating drydocks 76
Marine railways 6
Buildings for shipbuilding 7
Mechanical lifts 1
It is difficult to classify many facilities into either a ship-
builder or ship repair category a? many shipyards are engaged
in both shipbuilding and repair/maintenance in various degrees.
The percentage of work mix varies widely throughout the industry
as well as from year to year at a single shipyard. The quanti-
ties and specific types of paint used in facilities primarily
engaged in shipbuilding differ from those used at repair facili-
ties and therefore the functions of the shipyard?1 facilities is
important to this study.
4.2 GENERAL PAINTING PRACTICES
Shipbuilding includes painting the entire ship, both the in-
terior and exterior. The inside areas include living spaces,
machinery spaces, cargo spaces, tanks, and voids. After the
ship is added to the owner's fleet, coatings on the decks,
superstructure, and most interior spaces are maintained by the
ship's crew whil£ the ship is either in port or underway. The
percentage of this type of painting depends on the vessel use
(i.e., cargo or passenger), type of cargo and location of the
ship's travel routes.
There are noticeable differences between painting a ship during
construction and repainting as commonly done by repair facili-
ties. Since it may take 1 to 3 years to construct a ship,
painting is necessary to avoid corrosion during construction as
well as being an obvious part of the finished product. Ship-
builders usually begin applying a paint system at the initial
stages of construction. As steel plates are moved into the
area where sections or modules are to be built, the plates are
routinely cut to specifications, shot peened to remove mill
scale, and primed as the module is being built. Sections are
constantly being reblasted and repainted until they are fitted
together and paint can be applied to the complete hull and other
areas. The internal areas of the sections are coated quite
often before the sections are joined. The total painting system
of a new ship typically costs as much as 15 percent of the
total purchase price.
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Repair yards having drydock facilities are generally involved
with repainting of hulls. This is a convenient time for repairs
to be done simultaneously on propulsion systems, steering
systems, or whatever else is necessary. The work usually
consists of blasting the hull and applying paint. Surface
preparation is done to various degrees, ranging from a light
blasting through commercial blasting to white metal blasting
depending on the ship owner's specifications. Military vessels
commonly receive white metal blasting at drydock visits. The
hull then typically receives three paint systems: a primer; a
mid-coat; and a topcoat. The keel is coated with the highest
amount of antifouling additives in its topcoat. The area
between the waterline when empty and the waterline when carrying
a full cargo load is painted with less antifoulant, and the
free-board area is painted with the least amount of antifoulant.
The reason behind the judicious use of antifoulant is cost.
Keel paint containing the highest concentrations of antifoulant
typically costs as much as $13.20 per liter ($50 per gallon).
4.3 GEOGRAPHICAL DISTRIBUTION
Although the majority of shipyards are located on the seacoast,
there are a few yards located in the Great Lakes and on major
navigable rivers such as the Mississippi.
Table 4-3 shows the 10 areas and their associated port groupings
into which the United States is divided. Also shown is the
number of Code A shipyards in each area. Shipyards with topside
only facilities were not considered.
Area
West Coast 1
West Coast 2
West Coast 3
Inland Waterways
Great Lakes
Cast Coast 1
Bast Coast 2
East Coast 3
San Juan, P.R.
Gulf Coast Area
Table 4-3
Concentrations of U.S. Shipyards
Port Groupings
Seattle-Tacoma, Portland, Alaska
San Ftancisco Bay, Hawaii
San P^dro-Los Angeles, San Diego
Portland-Bath, Portsmouth, Boston-
Quincy-Newport, Groton, Conn.
New York, Comden-Philadelphia-
Wilmington, Baltimore, Norfolk-
Newport News
Wilmington, N.C., Charleston-
Savannah, Jacksonville-Miami
Tampa-Panama City, Mobile-
Pascagoula, New Orleans, Texas
Code A
Shipyards
8
7
5
3
6
7
18
2
14
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Eight shipyards in Virginia, Louisiana, Texas, California,
Florida and Washington were visited to gather data for this
study.
Regional climatological differences are important factors in
the use of paint during the colder months of the year. While
shipyards in Southern California, for instance, are able to
paint most of the year, shipyards in the northern New England
states may experience cubstantial periods of unsuitable painting
weather due to freezing conditions. Northern shipyards some-
times alleviate this situation by sending ships to southern
ports during inclement weather conditions for painting. The
impact of these actions is that during the winter months VOC
emissions from ship painting will increase in the south and drop
in the north.
The use of certain solvents due to weather is another geographi-
cal factor. An example is the occasional use of alcohol as a
solvent additive to uatei.Sorne zinc primer in colder weather.
Great Lakes shipyards generally do not conduct short term
repairs during certain winter months due to poor painting
conditions and the inability to move ships because of ice. In
recent years. Great Lakes shipping had been halted during winter
months because Coast Guard icebreakers have reduced service to
the Great Lakes.
As opposed to ships operating in and subject to pa.Xtwater
attack, there are little or no antifoulants applied on ships
operating in the Great Lakes. In addition, paints used in Great
Lake shipyards and inland waterway shipyards are not required to
contain the same anti-corrosive agents as paints used on ocean-
going vessels.
4.4 FREQUENCY OF PAINTING
The amount of VOC emissions as a result of ship painting will
vary directly with the nuuiosr of times the ship is painted over
its lifetime. It is therefore important to understand the
considerations involved in determining the time between ship
paintings. The predominant factors are:
1) Geographical operation of the ship
a) Ccean versus fresh water
Saltwater is more aggressive toward metals than is
freshwater and, therefore, lessens the time between
paintings. The constituents of ths paint applied are
also affected. Ships used exclusively in the Great
Lakes, such as iron ore carriers, generally are not
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coated with antifoulants because of the absence of
barnacles in fresh waters. The ma]or problem .'.«••
corrosion of the hull, whereas with oceangoing
vessels the major problem is biotic fouling below the
water line.
b) Tropics versus cc.Mer climates
Temperature influences biotic fouling. Ships mainly
operating in the upper latitudes encounter less fouling
due to slow biotic attack and a slower rate of chemical
attack than do ships operating in the tropical regions.
2) Type of paint used in previous painting
The type of paint previously used may determine whether
a ship can be painted over with a light surface cleaning
or must be blasted heavily prior to painting. The cost of
blasting is an important economic factor in deciding which
paints to use as it may account for as much as 70 percent
of the total resurfacing cost.
3} Type of service (e.g., cargo or passengers)
The type of cargo hauled relates to the amount of painting
that can be performed while the ship is underway. For
example, passenger cruise ships will not be painted to the
extent that an oil or a cargo ship will be while underway.
This means that more painting must be done during drydock
time for cruise ships, whereas cargo vessels may drydock
only to get a hull painting while the remainder is done by
ship's hands. Painting underway represents a very small
portion of the maintenance painting done.
4) Owner's maintenance schedules
The owner's maintenance schedule influences time between
paintings. A scheduled maintenance of ship's equipment
may coincide with paintings. An owner may not be vitally
interested in the aesthetic value of a new painting on an
older ship and may lengthen time between paintings.
Conversely, a large oil company may repaint its flagship
often.
5) Military versus civilian painting requirements
Military versus civilian painting requirements differ.
The military will use military standard hull coatings
and frequently blast to white metal when drydocked. Ship's
hands constantly repaint che remainder of the ship while in
port. Also, fleetwide tines between paintings for
various classes of ships have been adopted whereas private
10
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shipowners decide painting schedules on an individual
basis. Military ships routinely use as much as 5 times the
antifoulants in hull paint as do civilian ships.
6) Percentage of time a ship is underway
The amount of time a ship spends underway also influences
the tine between hull paintings. If a ship is actively
transporting cargo from port to port and spends little
time waiting to on-load or off-load cargo, it is less
subject to fouling as compared with a ship that may be at
anchor for considerable lengths of time. Prime examples
of this are naval vessels which frequently spend large
amounts of time in pert.
7) Use of cethodic hull protection
Many ships have cathodic anticorrcsion systems. If operat-
ing properly, they extend the time period between hull
paintings. The cathodic system can, if operating improper-
ly, destroy a paint system by operating on excessively high
currents. Metal castings, such as zinc alloy, are electri-
cally connected to the ship's hull and act as sacrificial
anodes. The anodes corrode preferentially to the iron hull
of the ship. Silty water will frequently abrade paint from
the hulls of ships and without cathodic protection the ship
would have to ba drydocked immediately or suffer severe
corrosion problems.
8) Cost of fuel
The cost of fuel indirectly affects the time between
hull paintings. Since fouling creates a hydrodynaiaic drag
on the hull, a barnacle-laden ship will use raoire fuel and
travel slower than a recently painted ship making the
same voyage. With the ever increasing cost of fuel and
costs of operating a ship, many owners drydock their ships
for barnacle removal and repainting more frequently. One
other option is to use more expensive high performance
antifouling paints to prolong periods between paintings.
The net impact of higher fuel costs is to increase the
frequency of drydock visits.
4.5 QUANTITIES OF PAINT USED
When a ship is to be drydocked for maintenance and/or a hull
repaint, the ship's owner usually provides the hull paint. In
the case of the military, the yard supplies paint formulated
to military specifications which is generally a low solids
type. The civilian ship owners are generally represented by
paint manufacturers' representatives who oversee the cleaning,
11
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surface preparation and painting of the ship. The paint repre-
sentatives act as QA/QC personnel to assure the work is per-
formed in an acceptable manner. Factors considered in deter-
mining the amount of paint on a ship include: the type of
paint, paint manufacturers' requirements, and the size and
design of the ship.
Type Of Paint
The type of paint influences the thickness of the application.
For example, a two-component, zinc-rich, pure epoxy may require
a wet film thickness of approximately 50 microns (2 mils)
whereas a bituminous coating usually used in voids may require a
wet film thickness of 500 microns (20 mils). This represents a
volume difference of 1000 percent.
Size and Design of Ship
The design of a ship is a factor in the amount of paint
required. Ships with a "V"-shaped hull may have less surface
area than a ship with a bulbous-shaped hull. Design also
affects the relative quantities of the different types of paints
used. The amount cf freeboard, for example, influences the
amount of anti-fouling paint versus freeboard paint used.
4.6 TURN-AROUND TIME
A typical ship may enter a drydock and leave within 5 to 10 days
if no major repair work is necessary. Ships typically receive
both maintenance and a hull blasting and repainting, which is
referred to as a "shave and a haircut", while in drydock. Since
the ship is completely out of the water, repairs can be carried
out on equipment otherwise not accessible. The overall cost to
the ship's owner of drydock time is very high because costs
include not only drydocking and shipyard labor fees, but also
loss of income for the ship due to inactivity. With costs
running between $5,000 and $100,000 per day, ships are moved
through a drydocking period as quickly as possible. Many
shipyards operate around the clock for efficient use of time and
facilities. It is not unusual for a shipyard to service 70 or
more ships in one year.
12
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SECTTON 5
MARINE PAINTS
5.1 MAJOR PAINTS FOR MARINE APPLICATIONS
5.1.1 GENERAL
The source of VOC emissions from ship painting facilities is, of
course, the solvents in the paints utilized. All of the sol-
vents present in paint evaporate during either the application
of the paint to the surface being coated or the curing process,
to become what are known as VOC emissions. Conventional,
off-the-shelf paints vary in solvent content from 20 to 82
volume percent, while special paints may contain as little as 5
volume percent solvent. Using very low solvent paints to reduce
voc emissions is an attractive approach to solving the problem;
however, it has limited application in ship painting. This
section discusses the various paints used to paint ships, their
specific uses and the organic solvents associated with them, to
aid the reader in understanding some of the paint related
constraints shipyards are under with regard to VOC emissions
control.
Marine paints play a vital role in a chip's overall performance.
The paints have two purposes, to beautify and to protect the
ship from corrosion. Due to severe environments, iraripe paints
have to be high performance coatings. These high performance
coatings are formulated to meet specific factors such as,
location of the shipyard, application techniques, time of year
when painted, condition of the surface to be painted, interval
between maintenance, and type of service of the vessel.
Originally, paints used drying oils and natural resins as the
binders. Now, most coatings used in the painting of metal
surfaces are based on synthetic resins. Generally, synthetic
resins are binders that are complex, long-chain substances. The
choice of resin usually determines the possible means of appli-
cation and cure. Certain coatings require specific temperatures
to cure properly while others must be heated prior to applica-
tion. Some coatings require humidity to cure while others do
not. Humidity is of great interest to the industry, since it
influences the final decision as to which paint will or can be
13
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used. The solids content of paints is also of great interest
to ship painters as coatings with higher solids contents have
numerous cost and environmental benefits over coatings with high
solvent contents. Commonly used paints in the ship building and
maintenance industries are acrylics, alkyds, epoxies, poly-
urethanes and vinyls. These and other paints are discussed in
subsequent paragraphs. Tables 5-1 and 5-2 provide comparisons
ofc different marine coacings.
5.1.2 ACRYLIC RESINS
Acrylic paints contain from 52 to *8 volume percen_ VOC. One
liter (0.26 gallon) of this painc would contain 0.52-0.68 kg
(1.1-1.5 pounds) of V3C.
Acrylic paints are mainly used inside of the ship. ?*~eas of
application include internal Jecks, internal bulkheads, voids,
and painted surfaces inside the engine room.
In general, acrylics are pale in color, have a fairly high
tolerance for heat and display good uniformity and retention
of color and gloss, even upon exposure to heat, sunlight, and
ultraviolet light. Acrylic coatings offer one of the best
protections against chalking and discoloration. For this
reason, acrylics are used primarily as a topcoat over other
coatings. They are suitable when thin films are required
without a primer. Acrylics can be used in combination with
other resins such as epoxies, vinyls, and chlorinated rubbers.
This results in good adhesion and resistance to chemicals,
corrosion, and impact. '
Acrylics can be formulated to be either thermoplastic or thermo-
setting in either a waterborne or solvent-borne* system. They
also can be used as high solids coatings.
The following list illustrates some of the properties of acrylic
paints for coating metals.
• Waterborne - Thermoplastic
- Long-term protection in mildly corrosive environment
- Excellent appearance
- Low odor, low toxicity
*Solvent-borne is used in this report to mean organic solvent
borne.
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Tabla 5-1
Ccnfarison of Resin Systems
Piysical State Anti- Inorganic Chlorinated
of Coatings fouling Acrylic Zuic Alhyd Egp££ "rethane Vinyl Rubber
Water-borne
- Themoplastic
- Thermosettuig
Solvent-tome
- Thermoplastic
- Thetnosetting
High Solids
2-Garoponent System
X X
X X
X
feasible Use of
Coating
Klnet
Final Coat
Uttetwat
Method of
application
toller
Kir Spray
Airless Spray
finish
% of total Use*
X
X
X
X
XX
X
12.4
X
X
X
XX
4.9
X
X
X
XX
X
5.1
X
X
X
X
X
XX
X
31.9
XXX
XXX
X
X X
XX XX XX
29.0 4.1 4.2
X
X
X
XX
6.2
X = Observed or reference found
XX •• Host canton method
Blank = Ho reference found
• Figures represent data for the state of California in 1976. Solvent use is not
included.
15
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Table 5-2
Areas of Application for Ship Paints
Where Used Acrylic Alkyd Epoxy Polyurethane Vinyl Chlorinated Rubber
Superstructure
Topside Equipment
Decks
Hull-above water line
-below water line
Internal Decks
Internal Bulkheads
Oi
Voids
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Engine Room-surfaces
-machinery
Tanks X X
Cargo HoIds-wet x X
-dry x X
-------
- Cleanup accomplished with water
- Nonflammable
e Waterborne - Thermosetting
- Useful as primer or topcoat
- Excellent adhesion, flexibility and chemical resistance
- Outdoor durability
- May require infrared cure in some cases
• Solvent-borne - Thermoplastic (Lacquers)
- Can be used as a clear solution
- Can be used as the basis for pigmented coating
- Excellent durability
• Solvent-borne - Thermosetting (Enamels)
- Good gloss and color retention
- Application of higher solids than thermoplastics
- Greater chemical resistance than thermoplastics
- Outdoor durability is variable
• High Solid - Excellent hardness and gloss make it
suitable for use on metal.
5.1.3 ALKYD RESINS
VOC's associated with alkyd paints are mainly mineral spirits
and range in composition from 40 to 65 volume percent of the
paint. One liter (0.26 gallon) of this paint would contain
0.36-0.58 kg (0.8-1.3 pounds) of VOC.
Alkyd resins are one of the more popular resins for ship
painting and are used in a wide array of painting products.
Alkyd coatings can be applied to large portions of a ship—
inside and out. Areas of application include the super-
structure, topside equipment, weather decks, hull, internal
decks, bulkheads, voids, and painted surfaces inside the engine
room. They are moderate in cost and fairly durable. Many are
thermosetting, since they usually dry by reacting with air.
Thei?: versatility and high degree of compatibility with many
17
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drying oils (limited primarily to short oil types for painting
metal surfaces) and other synthetic resins, increases their
usefulness. Alkyds, in combination with other resins, produce
good adhesion, good heat resistance, and color retention. They
are often used as primers, undercoats, and topcoats for metals.
Alkyds may be formulated as water- or solvent-borne paints
making them ame.iable_to application by brush, roller, air spray,
and airless spray.
Entirely water borne alkyd resins are bc'ind by ester linkages
that are relatively weak. This makes them susceptible to
breakdown by weather, water, and chemicals. Also, the average
molecular weights of alkyd compounds are low compared to other
polymers, resulting in lower performance properties.
Solvent-borne alkyds, which are used most frequently in painting
metal surfaces, use mineral spirits in a range of 40 to 65
volume percent as solvent. Alkyds are cured by an oxidizing
reaction (thermosetting) and are useful as primers and under-
coats.
Alkyds may be modified with phenolic resins, styrene, vinyl,
toluene, acrylic esters, silicone intermediates, and other
resins, to enhance certain qualities. For example, silicone
intermediates will contribute added heat resistance and dur-
ability and as little as 5 percent melaraine-formaldehyde resin
will lessen curing time and increase hardness.
The versatility of alkyd resins also allows alkyds to modify
other resin systems. Ncn-oxidizing alkyds are used as plasti-
cizers in nitrocellulose lacquers, while thormcset acrylic
resins are used in highly color retentive baking enamels.
Occasionally, a small amount of an oxidizing alkyd will be used
to supplement these systems.
In summary, alkyds find many uses in ship painting because
of their cost, versatility, and compatibility with other resins.
See Table 5-1 for a comparison of resin systems.
5.1.4 EPOXY RESINS
VOC's used with epoxy paints are xylol, n-butyl alcohol,
naphtha, butyl alcohol, and aromatic hydrocarbons. These
compounds range in composition from 20 to 79 percent (vol.).
One liter (0.26 gallon) of this paint would contain 0.18-0.71 kg
(0.4 to 1.6 pounds) of VOC.
The many types of epoxy resins possible increase their versa-
tility. They are a preferred coating because of their superior
solvent, detergent, corrosion, and chemical resistance, and high
mechanical strength. These properties make epoxies extremely
18
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well suited to application on the superstructure, topside
equipment, decks, hull, voids, internal decks and bulkheads,
tanks, and cargo holds. On their own, however, their resistance
to heat and ultraviolet light is limited and epoxies must
therefore be used in conjunction with another coating. '
Epoxies cure by chemical means. This allows for polymeriza-
tion of the epoxies to proceed from the relatively low molecular
.weights of the coating "as applied" to the high molecular weight
polymers in the "final film," which characterize their superior
film properties. They can be formulated as water- or solvent-
borne systems, cr as high solids coats. They may be applied
using most methods. The compatibility of epoxies with other
resins further enhances th:ir utility and popularity. As a
group, epoxies are compatible in varying degrees, with amino
resins (melamine and urea formaldehyde resin); phenolic, vinyl,
and certain acrylic resins; and short-oil, non-drying alkyds.
They can be enriched with zinc to give galvanic protection or
modified with silicone intermediates for added heat resistance.
Epoxy systems useful for painting metal surfaces are primarily
amine-cured and polyamide cured. These are discussed below:
• Amine Cured Systems
As a two-component system with the curing agent added
just before use, they are specifically useful as heavy
duty coatings. Sometimes they can be used with littlo
or no cure.
The properties include good chemical resistance, tough-
ness and durability. This makes amine-cured epoxies
excellent for lining tanks. Amine-cured epoxies can be
formulated to very high solids levels thus reducing the
number of coats required.
• Polyamide Cured Systems
These resins are unique among epoxies in that they are
thermoplastic, yet they produce topcoat films that are
tough and flexible, chemical and abrasion resistant, and
have good adhesion. They also are useful as primers
because they give a high degree of adhesion. Because
they have the ability to cure at room temperatures and
dry rapidly, separate curing of this primer sometimes
can be eliminated with both primer and topcoat curing
together. In addition, because this primer has high
molecular weight and inherent superior corrosion resist-
ance, further savings can be realized by reducing the
required film thickness. Common solvents for these
thermoplastic systems are xylol, butyl alcohols,
aromatic hydrocarbons (e.g., xyler.e and toluene), and
naphtha.
19
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In ship painting, these coatings are generally used on
the exterior hull as an anti-corrosive coating from the
light load line to the rail and also as a tank coating.
With its superior resistance to chemical and mechanical
wear, this system is commonly used on decks of ships
cartying solvents.
5.1.5 POLYURETHANES
VOC's associated with polyurethanes are Cellosolve" acetate,
ethyl amyl ketone, and methyl n-butyl ketone. These compounds
comprise from 45 to 56 volume percent of the paint. One liter
(0.25 gallon) of this paint would contain 0.44-0.54 kg (0.98 to
1.2 pounds) of VOC.
Urethanss as a group are used in ship painting and noted for
their toughness, flexibility, high abrasion and solvent resist-
ance, weatherability, good adhesion, hiding power, gloss, and
color retention qualities. These properties make urethanes
extremely well suited to application on the superstructure,
topside equipment, decks, hulls, voids, internal decks and
bulkheads, tanks, and cargo holds. Urethanes can be applied at
high solids content and can be cured at low temperature, 7°C
(45°F). Polyurethanes are in use as primers and intermediate
coats.
Urethane resins are the foremost film-forming type of poly-
urethane. They can be formulated as either enamels or lacquers,
i.e., thermosetting or thermoplastic. Another polyurethane
resin is based on the reaction with water or moisture in the
air. This class of polyurethane is known as "moisture cure"
and, to varying degrees, is ttie basis for two-component (or
package) systems chat result in linear polyurethanes. The
previously mentioned polyurethanes produce linear polyurethanes
with varying cross-linkages. Higher functional polyols in the
urethane paints can be used to achieve a specific degree of _
cross-linking resulting in harder, and less flexible coatings.
Three basic types of polyurethane systems will be discussed.
They can be categorized as being oil modified, moisture cured
(one package), or two-component system.
c Oil modified urethanes are most similar to conventional
finishes. They are analogous to alkyd manufacture,
where a drying oil is reacted with a polyhydric alcohol.
Cure is achieved by oxidation. Metallic catalysts
(typically cobalt, manganese, and lead) can aid drying
while maintaining a resistant film.
o Moisture cure polyurethanes are typically one-package
systems and are useful for coating metal. The urethane
20
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as applied reacts with moisture to cure. This process
may be enhanced by added heat cure. Solvents for
these urethanes, which consist of 40 to 60 volume
percent solids, are ketones, esters, aromatic hydro-
carbons: specifically methyl n-butyl ketone, butyl
acetate, ethyl amyl ketone, monoethyl ether acetate
(Cellosolve" acetate), xylene, toluene, and some methyl
ethyl ketone and ethyl acetate. Although cure is
possible under ambient conditions as well as at elevated
temperatures, time limitations in application usually
requires the addition of catalysts, typically organo-
metals (such as cobalt, lead or tin), or amJLr.c-3. The
catalysts effect rapid cure and protect the outstanding
film properties of urethanes, making them useful as a
single, final coat. High performance polyether bajed
urethane coatings are most useful for metal surfaces.
These coatings may be applied by roller and air or
airless spray. Their rate of cure is dependent on the
amount of moisture in the air.
o Two-component (package) systems are gaining in popular-
ity for coating nvetal because of increasing energy costs
and the possibility of eliminating or decreasing cure
time and/or temperature. These urethanes on their own
are not particularly good film formers so a second
component is added as a coreactant. Any coreactant of
suitable molecular weight can be used. Common coreact-
ants are polyether, polyes'sr, and castor oil.
Typical solvents for two-component systems are cresylic
acid, Cellosolve" acetate, and diacetone alcohol with
toluol and xylol employed as diluents. These urethanes
must be mixed just prior to application, since they have
an average pot life of 6 to 8 hours. These coatings
then may be applied with standard air or airless spray
equipment. These coatings way contain toxic isocya-
nates; however, this problem is minimized by the use of
nonvolatile polymers rather than free isocyanate and has
not detracted from the use of this paint system. Air
supplied respirators should be on hand and overspray
should be carefully controlled.
Film thicknes-jes of 25.4 to 50.8 microns (1 to 2 mils]
are Common, with the coating applied at up to 80 percent
solids content. Two-component urethane systems often
are used as primers as well as final coats because of
their high ultraviolet protection. Urethanes have
excellent adhesion and will adhere to almost anything
except oily surfaces.
21
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Although their principal disadvantage is a 30 percent
higher cost chart some other coatings systems, two-
component systems give improved coverage and offer
solvent emission reduction. Most two-component urethane
systems are suited for air curing if little or no drying
heat is available, tee major considerations being speed
of any following operations. The rate of cure also can
be affected by the addition of catalysts to the coating,
such as amines for room temperature cure, or tin based
organo-metallics for intermediate temperatures.
5.1.6 VINYL RESINS
Vinyl paint solvents range from 53 to 82 volume percent of the
paint. One liter (0.26 gallon) of this paint would contain
0.48-0.73 kg (1.1 to 1.6 pounds) of VOC.
Vinyl coatings are used primarily by the Navy as anticorrosive
and antifouling coatings. Vinyl coatings can be applied to a
ship's hull, cargo holds, tanks, weather decks, superstructure,
and topside equipment.
Vinyl resins were among the first addition polymers to be
synthetically made and used in industry. Chemically speaking,
vinyls may include all polymers made from monomers containing
the vinyl group (H?C = CH -) and, therefore, could include not
only the common vinyl chloride, vinyl acetate, vinyl fluoride,
and vinylidene chloride polymers and copolymers (which will be
discussed in detail) but also polyethylene, polystyrene, poly-
vinyl butyral, styrene butadiene, polyacrylates, fumartes,
maleates, and methacrylates. The common pract.'-e in the coat-
ings industry is to limit the category to the former group. In
the latter group, those with application in painting metal
surfaces will be discussed at the end of this section. The long
carbon to carbon chains common to vinyl resins make them thermo-
plastic, with good abrasion resistance and durability. They are
chemically resistant, and, generally, the longer the chain, the
stronger and the less soluble the polymer, and the higher its
viscosity. This flexibility in formulation means that vinyls
can be truly dissolved in organic solvents as a solvent-borne
coating or dispersed as in a high solids. They also can be
formulated as waterbornes. Vinyls tend to chalk less than
epoxies when exposed to sunlight, but are generally inferior to
epoxies in abrasion and solvent resistance. 's
Vinyls an be used anywhere that is not continually exposed to
water. Vinyl paints dry by evaporation and are little affected
by temperature. They can be formulated for use either as
primers or topcoats.
22
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For the purpose of this discussion, vinyls are categorized as
follows:
o Vinyl chloride, vinylidene cl..^:ide polymers, and
copolymers
• Vinyl acetate polymers and copolymers
• Specialty vinyls
Those applicable for painting metal surfaces as in ships are
emphasized.
5.1.6.1 Vinyl Chloride (H2C <= CHC1) and Vinylidene
Chloride (H-C » CC1-)
2 2
The vinyl chlorides and vinylidene chloride polymers and co-
polymers will be discussed together because the chlorine atoms
common to both not only add to the mutual ease of polymeriza-
tion, toughness, and nonflammability, but they also share the
tendency to be unstable with heat 110 to 121°C (230 to 250°F)
or under ultraviolet light, splitting out hydrochloric acid
(KC1) and developing unwanted color. This problem can be dealt
with by using certain pigments, sunscreen agents, or heat
stabilizers that will reflect or absorb harmful rays. Vinyl
chloride resins can be stabilized by a number of additives:
• Lead pigment
o Organic-tin compounds, tin mercaptides
• Barium-cadmium-zinc complexes (not free ions)
c Calcium-zinc complexes (not free ions)
Vinyl chloride resin stability can also be controlled by second-
ary stabilizers, usually epoxides that are used in conjunction
with the additives mentioned previously.
Normally, selecting a stabilizer for a coating is relatively
easy because films are thin and any initial traces of HC1
can evaporate. Also, the ccating contains enough pigment to
protect the resin from light. Application on metal surfaces
containing iron or zinc ions, oven if just from a surface
preparation process, causes a potential problem because these
ions themselves can contribute to accelerated thermal discolora-
tion and actual decomposition cf coatings. This problem can be
23
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alleviated by chemical surface preparation, restricting pigment
selection to those not containing iron or zinc salts, using
primers, or adding heat stabilizers, such as an epcxy-tin _ .
combination or ureaformaldehyde resins to the coating itself.
Polymers of vinyl chloride can be formulated as water- or
solvent-borne, or as high solids. Each will be discussed
separately:
• Waterborne Vinyl Chloride and Vinylidene Chloride
Coatings; These are of -xtremely fine particle size
(0.1 to 0.2 microns). The vinyl chloride polymeto can
be modified with vinyl acetate, acrylic, or maleic acid
esters and plasticizers. Heat and light stabilizer?
often are added. Copolymers of vinylidene chloride may
be modified with acrylonitrile, acrylic esters, or vinyl
chloride.
e Solvent-Borne Vinyl Chloride-Based Coatings; The
solvents that are usually required are relatively
strong, polar solvents - ketones, nitroparrafins, high
purity esters, and some chlorinated hydrocarbons.
Aromatic hydrocarbons are used as diluents. Vinyl
chloride polymers are compatible with alkyds and with
some thermosetting resins, such as urea-formaldehyde.
There is a wide choice of pigments in solvent-borne
vinyl chloride polymers. The only restriction, already
discussed, ia the use of iron or zinc salts, which can
affect heat stability and performance on exterior
surfaces.
There are many metal coating applications of vinyl
chloride copolymers containing vinyl chloride maleic
acid, and vinyl acetate because of the improved adhesion
to metal due to the presence of carboxyl groups (from
maleic acid).
Top coats are usually cured at ambient temperatures,
primarily to volatize solvents, assure good bonding to
the primer and to bring up the gloss. If the top coats
are to be subjected to temperatures above 121°C (2509F)
during use, then a heat stabilizer, such as an epoxy-tin
complex, would be necessary. Pigmented top coats, with
baked finish, offer excellent properties of toughness,
durability, and chemical resistance. They are useful
for coating machinery, appliances, and metal ite.ns of
all types.
9 High Solids Vinyl Chloride-Based Coatings; Vinyl
chlorides of high molecular weight are often formulated
as high solids. These 'ligh solids coatings, often
24
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called dispersion coatings, differ from solution
coatings in that the polywer is not dissolved but rather
is suspended in a liquid medium (high solids are called
organosols), when the suspending medium, which influ-
ences viscosity, is a mixture of polar (dispersant) and
nonpolar liquids (diluents). Solvents commonly used in
vinyl organosols are ketones, preferably diisobutyl
ketone, esters, and glycol ethers. Common diluents,
which are really nonsolvents, are usually aromatic or
aliphatic hydrocarbons. When a liquid plasticizer
(basically nonvolatile) is the suspending liquid, these
high solid dispersions are called plastisols.
The same limitations concerning the use ot iron and
zinc as pigments or additives apply to vinyl chloride
high solids formulations of both types. The use of
heat stabilizers, especially tin mercaptide and epoxy
stabilizer (possibly with bar ium-cadcii urn-zinc com-
plexes), are beneficial. Otherwise, pigments and
extenders may be used as desired, taking note of their
influence on viscosity.
Unmodified vinyl organosols do not adhere strongly to
metals, even with high temperature cure, but they do
adhere well to cured solvent-borne vinyl primers.
Consequently, a two-coat system is effective and is
used where toughness, abrasion, and chemical resistance
are required.
Plastisols also do not adhere well to smooth, impervious
surfaces. Primers may be used, but because of the
solvent action of plasticxzers, there may be some
migration of topcoat into the primer. This problem can
be overcome by using thertaosetting primers that are
usually a combination of vinyl and heat-reactive resins.
Plaotisols are used on metal parts, and are especially
usetul where a tough, flexible wear layer is necessary.
High solid vinyls modified with carboxyl groups have
recently been introduced. They have better adhesion
and cross-linking properties than non-modified vinyls.
5.1.6.2 Vinyl Acetate-Based Polymers and Cogolymers
Polyvinyl acetate (CH3COOCH=CH2) polymers are normally
formulated as latexes for use 5s adhesives, paper coatings, and
paints. Some are formulated as powder coats with specialty
applications as industrial coatings. Their use on metals is
limited because the acetate side group, being bulkier than the
25
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chloride group in vinyl chlorides, keeps the chains from pack-
ing; therefore, the resin is less strong and more easily pene-
trated by solvents and moisture. This also tends to make their.
soften at lower temperatures. Conversely, by the absence of
the chloride group, they are more heat and light stable. They
are permanently thermoplastic and heat scalable.
5.1.6.3 Miscellaneous Vinyl Resins with Applications in
Painting Metal Surfaces
Polyvinyl butyral resins, considered a derivative of vinyl
acetate, usually has application in painting metal surfaces
as a wash primer or as a metal conditioner used to inhibit
corrosion. This is considered surface preparation and is not
covered by this study. A new zinc-rich primer based on poly-
vinyl butyral has been developed. The polyvinyl butyral is part
of the binder and displays the anticorrosive properties of the
wash primer.
5.1.7 CHLORINATED RUBBER
VOC's associated with chlorinated rubber paints are xylol and
mineral spirits, and comprise from 44 to 68 volume percent of
these paints. One liter (0.26 gallon) of these paints would
contain 0.40-0.61 kg (0.87 to 1.3 pounds) of VOC.
The marine industry has accepted chlorinated rubber coatings as
good performing, general purpose coatings. They offer outstand-
ing resistance to water and corrosive chemicals. Chlorinated
rubber coatings are applied to ships' superstructure, topside
equipment, and hull.
Chlorinated rubber paint can be applied by airless spray result-
ing in a high build which protects against corrosion with few
coats. These coatings can be applied at almost any temperature
with minimal surface preparation. This makes them ideal for
ships built or serviced during the winter time. Chlorinated
rubber paints dry by evaporation of the solvents so the ambient
temperature is not too important.
Chlorinated rubber coatings are not high performance coatings
although they are superior to conventional alkyds. The general
use has been primarily on external parts of the ship, except
machinery, due to their resistance to water. They are used
as primers, intermediate, and top coats on decks and hulls.
5.1.8 INORGANIC ZINC COATINGS
VOC's used in solvent-borne inorgcinic zinc paints are ethyl
alcohol, isopropyl alcohol, and Cellosolve". The VOC content
26
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ranges from 21 to 52 volume percent. Each liter (0.26 gallon)
of this paint would contain 0.17-0.41 kg (0.37 to 0.90 pounds)
of VOC.
These coatings offer excellent protection against corrosion.
The zinc reacts with oxygen to give zinc hydroxide which*further
reacts with carbon dioxide to yield a film of zinc carbonate.
Zinc carbonate is an insoluble film that retards further corro-
sion so that the metallic zinc is not depleted too rapidly,
thereby lengthening the life of the primer.
Inorganic zinc coatings cannot be attacked by near neutral
solvents or chemicals. They are therefore primarily used for
the protection of tanks and other areas requiring good resist-
ance to corrosion and mechanical stress.
Waterborne inorganic zinc coatings can be applied as long as the
temperatures are above freezing. Below freezing temperatures,
alcohol is frequently added as an antifreeze which adds to VOC
emissions.
Inorganic zincs can be applied by all conventional methods.
5.1.9 ANTIFOULING COATINGS
VOC's used in antifouling paints are xylol and methyl isobutyl
ketone, and range in composition from 39 to 60 volume percent of
the paint. One liter (0.26 gallon) of this paint would contain
0.35-0.54 kg (0.77 to 1.2 pounds) of VOC.
Antifouling coatings consist of antifouling agents bound into
surface coatings to control marine growth on a ship's bottom.
The coatings are formulated to release active compounds into the
water to kill or repel fouling organisms as they develop.
Three types of coating systems are Available as follows:
• Single Coat
This is the most common antifouling coating. The basic
principle is the timed release of antifouling agents at
a rate which will kill marine growth. Timed release is
important so that the coating does not lose its effec-
tiveness too soon.
• High Build
This system is based on periodic removal of old anti-
fouling paint to expose fresh new layers. When the
outer layer of antifouling paint is exhausted, the layer
is mechanically scrubbed off. This results in fresh
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toxin being released from the newly exposed paint layer.
There is a limit as to how often this can be done, which
varies with each paint formulation. There are systems
available that do not require repainting for up to five
years under certain operating conditions.
• Self-Polishing
This system relies on self-polishing properties whereby
the coating gradually wears away by friction of the ship
through water. The hull actually becomes smoother
resulting in fuel savings. As the coating wears away,
fresh toxins are released at a constant rate between
drydockings.
Since the antifouling coating is worn away, there are no
built-up layers of paint that must be removed prior to
recoating.
Antifouling paint may be applied by all conventional
methods—airless spray, air spray, roller, and brush.
They are easily thinned with xylene. The primary method
of curing is by evaporation of solvent at ambient
temperatures.
5.2 THE ROLE OF VOC IN PAINT
Paint consists of a binder, pigments, solvent and special
purpose additives. The binder determines the film formation
characteristics and the performance of the paint coating. In
its liquid form the binder is usually diluted by the solvent to
prepare the paint for application. The pigment imparts decora-
tive value, including color, gloss, light fastness, etc. Paint
solvents include any volatile liquid that acts as the vehicle
for uniformly dispersing paint solids—organic compounds,
water, or some combination of the two.
The nature and quantity of solvent in paint controls the consist-
ency to make the paint suitable for application. The choice of
solvent influences viscosity, setting rate, drying time, and
pigment dispersion. The degree of dispersion affects film
flexibility, hardness, strength, and weatherability. This is
even though solvents evaporate during drying and do not become
part of the paint film.
Aside froi? their use in paints, solvents also are used for
cleaning painting equipment. Because of its expense the sol-
vents are usually recirculated and reused until they can no
longer be used for cleaning. At this point they are usually
drummed for disposal. The quantities of VOC emitted from this
28
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source will vary depending OP. cleaning practices. Some yards,
for example, let the solvents evaporate as they are used without
attempting any recycle.
Many paints used in the marine industry are also common indus-
trial paints. A general description of solvents commonly used
in the paints is shown in Table 5-3.
Table 5-3
Description of Organic Solvents Used in Marine Paints2
Classification General Information
Paraffins
(AlXanas)
Aronatics
Alcohols
Este'-s
These exist in two forms: normal
paraffins and isoparaffins. Low
odor. As molecular weight in-
creases, volatility and solvency
decrease.
Usually based on the unsaturated,
six-carbon-ring structure of
benzena. High solvency snd
strong odor.
A hydrogen atom of an aliphatic
hydrocarbon is replaced by a
hydroxyl group. Water soluble.
Mild, usually pleasant odor.
Specific Compounds
Heptane
Hexane
Cyc Lohexane
These result from the reaction of
an alcohol and an organic acid.
Host cannon use in lacquers.
Pleasant odor.
Benzene, Toluene, Xylene,
Ethyl Benzene, Xylol
Tetranethyl Benzene
Nethanol Oiacetone
Ethanol Alcohol
Isoprcpanol Hexylene
Butanol Glycol
Methyl Isobutyl
Carbinol
2-Ethyl Hexanol
Cctanol
Sec-Amy1 Ethylcne
Acetate Glycol
Sec-Butyl Monoethyl
Acetate Ether
Ethyl Acetate Acetate
n-Butyl Acetate
Isoprcpyl Acetate
Cellosolve* Acetate
(Cellulose Acetate)
Methyl Amyl Acetate
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Table 5-3
Description of Organic Solvents Used in Marine Paints2
(Continued)
Classification General Information
Specific Conpounds
Ketones
These compounds are characterized
by the CO group. Usually bad
odor.
Ether -
Alcohols
These contain both an alcohol
and an ether group.
Substituted
Hydro-
carbons
These include compounds of
the type containing hydro-
carbons with attached nitro,
amine, chloro and sulfide
groups.
Pentoxone 2-Butanone
Hsthyl Ethyl 2-Hexanune
KGtone
Diisobutyl
Ketnne
Acetone
Iscphorone
Methyl Isobutyl
Ketone
hthyl Anryl Ketone
Glycol Ether(Butyl Cellosolve")
Dichlor Isopropyl Ether
Ethyl Ether
Diacetone Ether
Carbitol
Ethylene Glycol Monoethyl Ether
Allyl Glycidyl Ether
Ethylene Glycol Monobutyl Ether
Butyl Glycidyl Ethsr
Rjenyl Glycidyl Ether
Xylenol Glycidyl Ether
Cresyl Glycidyl Ether
McnochlorrLenzene
Dichlotobenzene
Nitrate thane
Nitrobenzene
Carbondisulfide
Urea
Cresylic Acid
Methyl Ethyl Ketoxine
Triethylamine
Diethy lamina
Diethylamino Ethanol
Chloroform
Carbon Ttetrachloride
Chloroethene
Trichloroethylens
Fterchloroethylene
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Table 5-4 shows the most common solvents associated with a
particular type of marine paint.
Solvent-borne coatings, by convention, refer to coatings formu-
lated with organic solvents as the dispersing vehicle. Gener-
ally, several solvents are used in combination. Solvents are
primarily straight chain or aromatic hydrocarbons. Despite
their high cost, oxygenated solvents are also used because they
are stronger solvents.
There are two basic types of solvent-borne coatings. They are
lacquers (thermoplastic) and enamels (thermosetting). Lacquers
contain thermoplastic resins that cure by solvent loss. The
paint film is held together physically rather than by chemical
forces. The binder in the dry film is chemically the same as it
was in the paint can. Enamels, on the other hand, undergo a
chemical reaction upon curing resulting in cross-linking of the
paint molecules. There are two mechanisms of chemical reaction.
One is by air oxidation, the other is by chemical reaction of
the binder without air taking part. Some examples of each are
listed below:
Thermoplastic, Physical drying; Chlorinated rubber, other
chlorinated resins, vinyls, accylics, and PVA emulsions.
Thermosetting, Chemical drying; Alkyd enamels, epoxies,
tar epoxies, polyurethanes, zinc silicates.
The following is a summary of advantages and disadvantages in
the use of solvent-borne as compared to waterborne coatings:
o Advantages;
- Suitable for application by most methods.
- Host common, therefore, readily available.
- Technology and equipment already developed and in
use.
- Reliable.
- Less sensitive to contaminants.
• Disadvantages;
- Air pollution is caused by emission of solvents.
- Fire hazard and exposure limitations demand large air
exhaust system to keep concentration of solvents
low.
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Table 5-4
Common Paint-Eolvent Systems
for Marine Applications
Associated VOC
(in order of highest use)
Mineral Spirits
Antifouling
Xylol
Methyl Isobutyl Ketone
Chlorinated Rubber
Xylol
Mineral Spirits
Epoxy (catalyzed)
Xylol
n-Butyl Alcohol
Naphtha
Butyl Alcohol
Aromatic Hydrocarbons
Folyurethanes
Ccllosolve" Acetate
Ethyl Aniyl Ketone
Methyl n-Butyl Ketone
Inorganic Zinc
(organic-solvent based)
Ethyl Alcohol
Isopropyl Alcohol
Cellosolve"
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A limited quantity of paint can be stored in an area
due to safety regulations.
Higher cost and questionable availability are pre-
dicted for solvents in the future.
5.3 WATERBORNE PAINTS
Waterborne paints get their name because water is the major
solvent. The paint resin may be dissolved or suspended in the
water. Despite their name, organic cosolvents are almost always
used to improve wetting, control viscosity, and disperse resin
and pigment. Water soluble resins usually contain around 20
percent organic cosolvents. Suspended resins may have less than
5 percent organic cosolvents. These cosolvents are primarily
oxygenated solvents (ketones, alcohols, glycol ethers) and
amines. Waterborne paints are currently available for resins
such as epoxies, acrylics, polyvinyl acetates and inorganic
zinc. Both dissolved and suspended resin paints display proper-
ties similar to conventional solvent-borne paints. These are
weather and chemical resistance, durability, and toughness.
Freezing can be a problem for waterborne paints. Emulsion
waterbornes are more of a problem than solubles because the
cosolvent content is only about 5 percent and the freezing point
of the paint is not significantly reduced. Soluble waterbornes
usually are not affected by freezing, whereas emulsions are
often destroyed.
Waterbornes may be either thermoplastic or thermosetting.
Depending on the particular resin, waterbornes can be applied
by brush, roller, and all forms of spray. Table 5-5 compares
solids content by type of paint.
Table 5-5
Percent Solids by Type of paint
Type of Paint % Solids (by volume)
1. Waterborne 5-35
2. Solvent-borne
a. Lacquers 15-35
b. Enamels 25-35
3. High Solids
a. Medium High Solids 45-70
b. High Solids 60-95
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There are unique advantages and disadvantages associated with
waterbcrne paints. Due to the conductivity of water, special
care must be used when applying electric current to an applica-
tion process (i.e., electrostatic spray) to make sure all wiring
is grounded or insulated. Because water is corrosive, exposed
hiotal surfaces in spray booths have to be protected. Curing of
uaterborne paints is affected by temperature and humidity.
Waterbornos must be properly cured or their resistance to water
will be decreased. Waterbornes have definite fire and explosion
advantages because of the low organic solvent level.
The following is a summary of advantages and disadvantages to
consider when using waterborne as compared to solvent-borne
paints:
• Advantages;
- Less unpleasant odor is experienced.
- They are non-flammable.
- Reduced solvent emissions are possible.
- A cleaner, healthier, less toxic environment is
provided for workers.
- Waterbornes use conventional application techniques.
- Waterbornes use conventional equipment with ease of
conversion and minimal disruption in many cases.
- Color, impact and corrosion resistance, gloss, and
weatherability compare favorably to solvent-borne
coatings in many applications.
- Formulation not primarily dependent on petroleum-
based solvents whose availability and cost have an
uncertain future.
- Storage life is good.
- Although the surface to be painted needs to be clean
before application, no revision of surface prepara-
tion procedures is usually required.
- There can be a reduction in air atomizing pressure
and agitation for waterbornes over solvent-bornes.
- Handling costs can be reduced because an 8-hour
supply can be stored at a booth without violating
fire regulations.
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- Waterbociie coatings can be applied over sol vent-based
coatings.
• Disadvantages;
- Protection from freezing is required for some water-
borne coatings.
- For use with electrostatic or electrodeposition
operations the system must be electrically insulated.
An alternative is to use intermediate reservoirs that
are insulated and isolated.
- Humidity and temperature are very important as they
affect evaporation rate.
- Wet-on-wet application may not be possible.
- Metal surface preparation ar.d cleaning are often
more critical.
- Efficiency of waterbornes using airless electro-
static equipment ir lower than that of solvent-borne
coatings.
- Due to their generally higher heats of evaporation,
longer curing times and higher temperatures, drying
times will usually be affected.
- Air drying is not reliable due to humidity problem.
- The performance of woterborne paints has not, in
general, been satisfactory for marine applications.
Anticorrosive coatings are the exception to this.
5.4 TRENDS IN INDUSTRY
5.4.1 THE USE OF TWO-PART REACTIVE PAINTS
Six shipyards supplied estimates of the change that two-part
reactive paints have made in their total paint use. Half the
shipyards showed an increase in the amount of two-part reactive
paints used, while the other half reported no change. Two other
shipyards did not have the figures available. The data is shown
in Table 5-6.
These paints cure by the reaction of two ingredients, thus the
name "reactive." Two-part paints may be mixed just prior to
application or they may be mixed in the head of the paint spray
gun.
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Table 5-6
Two-Part Reactive Paint as Percent of Total Paint Use
Shipyard Current Five Years Ago
1 60 30
2 50 0
3 60 45
4 50 50
5 55
6 15-20 15-20
7 -
8 - -
The advantages o£ two-part paints include: higher efficiency of
Application, less solvent being used, lover shipping cost,
possibly fewer coats of paint need be applied, and possibly a
reduction of air flow inside the ship or spray booths because
of their lower solvent content.
As the paint components polymerize, the molecular weight of the
solids in the coating increases. From Table 5-5, it can be seen
that high solids paints contain an average of 50 percent more
solids than low solids paints, and generate less solvent emis-
sions because of their low solvent content and higher efficiency
o£ application.
5.4.2 THE USE OF WATERBORNES
Four of the eight shipyards visited use waterbornes in some
measurable quantity. The highest use was only 5 percent of
total paint use. From i/.-erviews, it was apparent that either a
shipyard uses waterbornes at ~5 percent of total paints consumed
or it uses hardly any. The only waterborne paints reported in
use were coal-tar emulsions and inorganic zinc primer. Very
little waterborne paint is being marketed for marine use besides
these two uses.
Waterborne paints have not g:-ined major acceptance in ship
painting because they generally offer no significant performance
advantages over commonly used solvent-borne paints and fre-
quently cost more. As noted in Section 4, the shipyards gener-
ally do not have the option of selecting the paints they use as
this is dictated by the shipowners.
Table 5-7 presents the survey results with regard to the use of
waterborne paints.
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Table 5-7
Waterborne Paint as Percent of Total Paint Use
Shipyard Now Five Years Ago
1 50
2 50
3 <1 <1
4 0.1
5 <1 <1
6 00
7 00
8 -
5.4.3 MARINE PAINTING RESEARCH
Several organizations are currently performing research in the
fi-2ld of marine paint systems. The National Shipbuilding
Research Program in conjunction with the Maritime Administration
is conducting research that tests currently available commercial
paints rather than develop new paint systems. The test program
subjects commercial pai>its to various marine conditions to
determine their suitability for use in or on ships.
Project PACE (Performance of Alternate Coatings in the Environ-
ment), sponsored by the Steel Structures Painting Council,
evaluates the durability of new types of paints, raw materials,
and surface preparation methods for structural steel. The
program provides information on alternative coating systems
designed to prevent corrosion while complying with present and
expected legislation covering pollution. Other studies that may
be beneficial to marine painting include a project to optimize
paint film thickness.
The Naval Ship Research Center of the Navy Department researches
paint systems and paint application equipment. The paint system
research includes testing and evaluation of new paint formula-
tions as well as reformulations of currently available paint.
Antifouling paint currently accounts for 75 percent of the R&D
budget, with the remainder of the budget going for anticorrosive
paints. Several programs also exist for the development and
testing of waterborne paint. Two of these programs are for
interior and topside maintenance paints. Early results from
these two programs indicate more premise for waterborne paints
in raarine uses than earlier research.
The primary aim of research undertaken by peint formulating
companies used to be substitution of organic solvents by water.
However, formulators are now searching for new materials and
systems to cope with the problems of energy demand, toxicity,
37
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cost, and odor. The need for better equipment in the applica-
tion of high solids paints is also being emphasized. Anti-
foulant coatings research is trying to extend service life
beyond 24 months. More frequently, paint formulators are coming
out with paints that provide up to 30 months protection. With
antifoulants comprising the major portion of maintenance
painting, VCC from repair facilities can be expected to decrease
in the future based on life-cycle emissions. Several companies
have also come out with computer generated paint maintenance
programs. A custom-made hull paint maintenance program for
individual ships has demonstrated a reduction in maintenance
painting. New formulations also include 100 percent solids
materials that are a solvent-free coal tar epoxy or a solvent-
free pure epoxy. Besides decreasing VOC emissions, solvent-free
materials can be used without the danger of explosion.
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SECTION 6
VOC EMISSION CONTROL TECHNOLOGIES
6.1 INTRODUCTION
There are three possible approaches toward reducing the amount
of VOC emissions from a painting operation:
1) Modify the paint formulation either to contain less
solvent or to have a longer service life
2) Capture the emissions before they are released to the
environment and then either reclaim or destioy them
3) Improve the paint application technology in order to
increase the paint transfer efficiency and reduce the
amount of paint used.
These approaches are not mutually exclusive and any combination
of the three is worth considering. Each approach has con-
straints which may make individual technologies inapplicable for
ship painting. For example, powder coatings virtually eliminate
VOC but because of high curing temperatures, among other rea-
sons, they cannot be utilized for hull painting.
This section will explain how each of the three approaches can
be applied to the ship painting industry, the associated con-
straints, and the related trends in industry.
6.2 MODIFICATION OF PAINT FORMULATIONS
As detailed in Section 5, organic solvents (VOC) play a vital
role in the formulation, application, and cueing of paints and
except in a few instances cannot be eliminated entirely from the
formulation. Table 6-1 shows the VOC volume percent of various
paint types used in ship painting. It is clear from the table
that the amount of VOC in paints is both variable and substan-
tial ranging from 2" to 82 voluma percent.
In recent years there has been significant progress in reducing
the VOC content of paints which is attributable to environmental
and economical factors. Environmental regulations in industries
39
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Table 6-1
Solvent Proportions by Type of Paint
Volume •'ercent
Type of Paint Solver^.
Acrylic 52-68
Alkycl 40-65
Antifouling 39-60
Chlorinated Rubber 44-68
Epoxy 20-79
Inorganic Zinc 21-52
(organ.'c solvent)
Inorganic Zinc 23-43
(water solvent)
Polyurethane 45-56
Vinyl 53-82
40
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other than ship painting have forced paint foripulators to
develop low solvent paints to meet the demands of their cus-
tomers. Aside from regulatory compliance, economical benefits
were also observed and rrost of these benefits have been directly
transferable to marine coatings.
Economic benefits accrue partially because, a? discussed
earlier, solvents evaporate from paints totally and do not
become part of the coating. Less solvent in the paint leads to
direct savings because less solvent is evaporated away. Low
solvent paints may be applied in thicker layers which means that
fewer layers are required to reach a specified coating thick-
ness. Some low solvent coatings, for example, can be applied in
one application instead of four separate applications, for a 75
percent reduction in labor costs.
Another effective modification to paint formulations that
results in reduced life-cycle VOC emissions is the use of
high-performance coatings. Painting a ship every year will
cause twice the emissions associated with a ship painted every 2
years. For ship ownerj the overpowering reason for specifying a
high performance coating is cost rather than the environment.
When out-of-service time is considered, a day in drydock can
cost anywhere between $5000 and $100,000. While all high-
performance coatings have substantially higher first costs than
conventional systems, these costs are more than offset by the
coating's effectiveness and durability and the resultant reduc-
tion in out-of-service time.
Shipyards visited as part of this study indicated increased
use of high-solids coatings and increased acceptance of
waterborne coatings over the past 5 years. Utilization of
high-performance coatings also is rising rapidly. All shipyards
consulted expressed a preference for state-of-the-art paints
over those used in the past (many of which are still required
for military applications). This trend has not been directly
due to environmental regulations but has developed primarily
because of the costs associated with protecting a ship's hull
from corrosion and control of biotic fouling which has becc.iie
critical with the high costs of fuel. The effects of this trend
on the amount of VOC emissions from ship painting operations are
unknown due to a lack of data; however, a net reduction in
emissions would b* expected.
6.3 CAPTURE TECHNOLOGIES
Paint booths or hoods are commonly used throughout the metal
finishing industry to contain and remove emissions from painting
operations. Exhaust from these systems can be ducted to an
incinerator where the VOC are destroyed or to a carbon absorp-
tion unit for removal before being released to the environment.
41
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The nature of ship maintenance work, however, would make any
kind of enclosure system very expensive from both a capital
investment and energy cost viewpoint. Enclosures would have to
be designed specifically for each facility and would be some of
the largest structures in the world. Air flows would be large
and the VOC content of the air would be very low requiring the
energy consumption fox incineration to be very high. Such a
system would be clearly unreasonable.
An alternative system would be to have a small traveling en-
closure just large enough to cover the immediate area being
painted. As it is likely that several of these hoods would be
operating en a ship at a given time, a maze of exhaust hoses
with potentially explosive gas mixtures would develop. The
safety problems would be complex and would include the problem
of flashbacks from the incinerator to the painter through the
exhaust hose. The shape of the hull would dictate what kind of
support mechanism could be used for the hood and may make
support infeasible. If it was feasible to design such a system
it would probably collect only a portion of the VOC being
emitted. Some solvent would evaporate from the surface while
the paint cures after the hoed has left the area.
No references were found indicating that capture and destroy or
recovery systems for VOC emission control are being used or
considered by the ship painting industry.
6.4 EMISSION REDUCTIONS BY IMPROVIi-iG APPLICATION TECHNOLOGIES
6.4.1 OPTIONS FOR APPLYING PAINTS
The choice of a particular paint application process reflects
consideration of: the material to be coated; the product
configuration; the desired coating properties; the extent
of production; environmental considerations; and other factors.
When considering the painting of ships, processes such as flow
coating, dip coating, electrodeposition, and barrel coating are
easily eliminated in spite of their high transfer efficiencies
because they are physically infeasible. Conventional brush and
roller application is far too labor-intensive for the bulk of
ship painting and is used only where necessary. If the proper
technology were developed, roller coating could become an
attractive alternative application technology for the large
essentially flat surfaces present on a ship because it has
nearly a 100 percent transfer efficiency. Powder coating by
any application process is eliminated because of the properties
of powders which, among other problems, require a high-tempera-
ture cure. Ship painters are thus left with spray painting as
the only practicable application technology available to them.
As spray painting can be extremely wasteful of paint and accord-
ingly generate very high VOC emission rates, it is useful
42
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to understand the technology in order to know its limitations
and potentials. Air and airless spray, and electrostatic ver-
sions of both are available to ship painters and are described
in the following section.
6.4.2 SPRAY PAINTING TECHNOLOGIES
Spray painting is by far the most common application method and
can be Uoed with almost all varieties of paint to coat most
types of materials.
The main components of a typical spray painting system are a
pumping system, an atomizing system, and a spray gun.
Spray painting is accomplished by driving finely divided parti-
cles onto the surface being coated. Varieties of spray applica-
tion include air spray, airless spray, and electrostatic spray.
Air spraying utilizes high pressure air to atomize paint and to
drive it to the surface being coated. An air atomized sprayer
may be either hand-held or automatic although ship painting is
not very amenable to automatic systems. Hand-held sprayers are
very useful for painting unusual contours and complicated shapes
because of their portability. The greatest strength of hand-
operated spray painting is its versatility. Many different
operating conditions can be accommodated by skillful sprayers
and careful solvent blending. At this writing, approximately 20
to 30 percent of the paint used in shipbuilding yards is applied
by air spraying.
Compressed air is used in air spraying as the driving force.
The compressed air flow and the pressure for the paint and
atomizing lines are regulated. The fluid lines connect to the
paint pot which may supply one or several guns through the paint
line. The atomizing air line connects directly between the
pressure regulator and the spray gun (see Figure 6-1). The
spray gun may be pressure or suction fed. The pressure gun \s
used to paint large areas rapidly. The suction-fed gun forces
high velocity air across the nozzle creating a vacuum in the
feed line which draws the paint up into the nozzle to be atom-
ized. Both pressure fed and suction fed systems are commonly
used in shipyards.
Air spraying produces large quantities of overspray caused by
turbulence of the high velocity air impacting and rebounding
from the surface and carrying paint with it. This wasted paint
is referred to as "overspray." Air spraying has only a 40 to 60
percent transfer efficiency because of the paint loss due to
overspray. The skill of the painter has a significant impact on
the transfer efficiency as angle of spray and distance from gun
43
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(A)
COMPRESSOR
PRESSURE
REGULATOR
AIRLINE TO CUN
(Atomizing Line)
SPRAV
CUN
Air Spray
SPRAY
CUN
Airless Spray
Figure 6-1. Paint Spraying Systems
44
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to object, both of which effect efficiency, are at the control
of the operator.
Airless spraying is a method of spray application that does not
directly use compressed air to atomize the paint or other
coating material. Hydraulic pressure is used to atomize the
fluid by pumping it at high pressure 35 to 316 kg/sq-cm (500 to
4500 psi)) through a small orifice in the spray nozzle. As the
fluid is released at these high pressures, it is separated into
small droplets resulting in a very fine spray. Water, for
example, is hydraulically atomized by the fine spray adjustment
on a garden hose nozzle; however, it is accomplished with low
pressure because of the low viscosity of water. Paint and other
coating materials have a higher viscosity and therefore require
higher pressures. The fluid is discharged from a small nozzle
orifice at such a high velocity chat the material tears itself
apart. Sufficient momentum remains to carry the minute parti-
cles to the surface.
Airless spraying can accommodate much more viscous paints than
air spray, which has aided the acceptance of low solvent paints
by industry. Airless is used widely to apply zinc primers and
other highly pigmented paints and is especially useful for large
objects. There has been a definite trend in the ship painting
industry toward higher utilization of airless spray.
Since air is not used to atomize the paint, the term "airless"
is used to describe this method. Turbulence and blow back are
greatly diminished due to the absence of air. Consequently,
higher paint transfer efficiencies of up to 70 percent are
realized.
Air pressure is required to operate an air motor which powers a
reciprocating airless fluid pump. The pu.np develops fluid
pressures at a given ratio depending on the size of the air
motor piston and the effective area of the fluid piston. For
example, a pump rated at 25:1 develops fluid pressure 25 times
the air pressure applied to the air motor. For 7 kg/sq-cm (100
psi)air pressure, 176 kg/sq-cm (2500 psi) fluid pressure results.
Another option available for spray painting which can reduce VOC
emissions is the use of hot spray. Very viscous paints are made
pumpable b> heating rather than thinning with solvents. In hot
spray, the paint solution is heated, usually to an operating
temperature of 38 to 66°C (100 to 150°F). Hot airless spray
reduces the amount of overspray that contaminates a vork area
and wastes paint. Because the viscosity of the solution is
lowered by heating, much higher solids content is achievable
with hot spraying, thus lessening the amount of solvent
evaporated into the atmosphere. Higher solids painting also
permits a thicker film buildup per pass of the spray gun without
risk of runs cr sags in the coating.
45
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Electrostatic spray painting is accomplished by placing a high
voltage electrical charge on each particle of paint. The object
to be coated is an electrically conductive ground. Some
of the paint o^rticles that would normally miss the work will
now be attracted to the edges and back side of the work. This
effect is commonly referred to as the "wrao around" effect and
represents the principle advantage of electrostatic spraying.
This effect offers little benefit in the painting of ships
hulls.
The material can be atomized in one of two ways: The first is
to use the electrostatic force created by high voltage differen-
tial between a paint dispenser and the ground^J wrirk. This
force tears the material apart effecting atomization and
deposits the material on the object.to be coated. No air or
hydraulic force is used. This method is sometimes referred to
as "true electrostatic painting." The material is fed to a
rotating disc or bell. A set speed will cause the material to
flow by centrifugal force to the edge, but not disperse. The
disc or bell is charged to 120,000 volts D.C. negative (excess
of electrons). As the object to be coated passes by the
rotating disc or bell, the material is pulled off by a current
exchange between '-he emitter and the product and is attracted to
the work. This type of electrostatic finishing is used by most
major appliance manufacturers because of the high required
production volume and uniformity of the parts to be coated.
These systems are generally not purchased but leased from
equipment manufacturers.
The second method is to atomize the material first, using air or
hydraulics as the force. The high voltage charge is then
induced into the spray pattern and
-------
• Extraneous forces, such as air movement opposing the
field force, must be avoided in the use of electrostatic
spraying. The necessity of outdoor spraying in the
painting of ships would limit application to calm days.
• The addition of electrostatic spraying equipment to the
airless equipment currently in use would add approxi-
mately $2500 to the investment cost of each spray unit.
• A power pack required for electrostatic equipment weighs
up to 200 pounds. The addition of this equipment would
severely limit the portability of spraying equipment.
• The use of electrostatic equipment requires special
safety considerations to prevent static discharges.
These precautions would be particularly difficult with a
portable unit.
e The conductivity of paint formulations is of critical
importance in the use of electrostatic equipment. Many
highly conductive paints cannot be applied with this
method.
Electrostatic application of paints to aircraft has recently
proven successful. This method is of utility in that in-
dustry because the surfaces being coated are nearly all con-
toured and only thin coatings are required. It appears that
there is little likelihood that shipbuilders will be attracted
to electrostatic application technologies.
6.4.3 NEW TECHNOLOGY
Technologies do exist which could greatly reduce or eliminate
VOC emissions during ship painting but considerable research
would be required to make the technologies applicable to ship
painting and, in addition, to develop the paints necessary for
the application. Ttie technologies would be UV or electron-beam
curing of paints which use little or no VOC as solvents. There
is no indication that such technologies are even being con-
sidered for this industry because of the many technical ques-
tions which must be answered.
One technology having some potential for reducing VOC emissions
was discovered and is unique to the ship painting industry. At
Norfolk Shipbuilding and Drydock Company a machine known as a
Docknight" is used to paint ships at a capacity rating of an
acre an hour. By keeping the spray perpendicular to the surface
and minimizing the number of paint overlaps it is expected that
the amount of paint required per ship would be reduced with
concurrent reductions in VOC emissions. No data are available
to quantify the savings. A technical description of the device
follows.3
47
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The Docknight"* is a welded traveling platform on which is
mounted one 781 kg-cal/min (73 HP) diesel engine for driving
hydraulic pumps, one 2890 kg-cal/min (270 HP) engine connected
to a triplex pump with an output of 9.5 liters/sec (150 GPM)
at 188 kg/sq-cm (2680 psi), an operator's cabin, three hydrauli-
cally operated paint pumps, and a base boom including the
electronics and hydraulics necessary to operate and automate
the system. Connected to the base is a working boom with an
attached work cage. The Docknight0, originally designed as a
waterblasting system, was custom built to NORSHIPCO's specifica-
tions to include spray painting capability.
The system has a vertical working range of 30 m (98 ft) from the
lowest point to the extreme height. Its range can accommodate
ships with a beam of 35.2 m (116 ft) to those with a beam of 44
m (144 ft). A lesser range is achievable with smaller ships.
On the end of the working boom is a wheel-activated sensor that
guides the working boom automatically to follow the contour of
the vessel's hull when the system is in its automatic mode. In
addition, there is a push-button indexing system that moves the
working boom up or down in increments of 1.1 m (3.6 ft) when in
the waterblasting cycle and 1.8 m (5.9 ft) when in the painting
cycle. The speed of travel is also adjustable in known incre-
ments. The speed of travel is an essential element in deter-
mining the mil thickness in the painting process.
The weight of the Docknight™ is 26 metric tons (23.6 short tons)
and it is supported on a rail by four vheels. Each wheel is
driven by an infinitely variable hydrai-lic motor. The Docknight'
position is held horizontally on the top rail by c,uide rollers
that run on either side of the vertical face of the rail.
In order to withstand the horizontal forces generated at the
lower extreme of the base boom, particularly when the base boom
and working arms are fully extended and perpendicular to the
side of the dock, the lower column roller is designed to coin-
cide with the safety deck in the drydock.
Four people are required to operate the Dockr.ight" in the
painting mode; one operator, one operating engineer, and two
paint handlers. Although the system was designed to pump paint
from 208 liter (55 gallon) paint drums, the current procedure
employs the use of an open 208 liter (55 gallon) drum v/hich is
manually replenisned by two paint handlers using 19 liter
(5 gallon) pails.
It must be pointed out that this system was designed specifi-
cally for use at NORSHIPCO and the floating drydock was modified
substantially to accept the Docknight". The systern is not
adaptable to many drydocks because of the structure of the
dr-cks. As would be expected, the system is quite expensive with
48
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NORSHIPCO's unit co-jting $1.5 million excluding modifications to
the drydock.
The impetus for installing the DockniCjht" system at NORSHIPCO
was to speed up ship painting in order to decrease turnaround
time making the shipyard more attractive to potential customers.
While a decrease in paint consumption may have been anticipated,
any environmental benefits are welcome but incidental to the
primary driving force which is economics. The Docknight" has
been modified to recirculate cleaning solvents, which serves the
double function of reducing operating costs by reclaiming
solvent and also reducing VOC emissions.
49
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SECTION 7
ESTIMATION OF NATIONAL VOC EMISSIONS
FROM MAJOR SHIPYARD PAINTING
Many factors contribute to making an accurate determination of
the quantities of VOC being emitted from ship painting opera-
tions a very difficult task. Marine paints, for example, are
also used to paint oil derricks and other structures exposed to
seawater and records for these alternative uses either do not
exist or are not readily available. Alternatively, some paints
with general industry use are also used in ship painting and
records of end uses are not maintained by paint formulators.
Additionally, some ships supply their own paint to drydocks from
foreign sources. Even if total gallonage records were avail-
able, each type of paint has its own solvent associated with it
at varying volume percents. Because of these problems and
others, it was decided to make several estimates based on
independent approaches. By using the approaches described
below, a range of VOC emissions was developed. All values
were well within one order cf magnitude, indicating that a
reasonable degree of confidence is associated with them.
The first approach was to utilizs the data obtained during the
visits to shipyards to arrive at an e;.tiuate of the total
VOC emission from painting of ships baseJ on employment and
paint consumption. Table 7-1 presents a summary of paint use
and employment data for the shipyards visited.
Shipyards were divided into three categories for analysis
because the significance of the painting operation in relation
to the total work load depends on the nature of the shipyard.
These categories are:
1. Primarily Construction
2. Construction and Repair
3. Repair Only
The ratio of paint use to employment was determined in each
case for which data was available. The expected value of this
ratio was found for shipyards falling into each of the three
categories listed above. The expected value of annual paint
50
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Table 7-1
Paint Use and Employment
at Shipyards Visited
Shipyard
Primary Current
Function
Paint Use
1/yr (Gal/Yr)
Employment 1/man/yr (Gal/Man/Yr)
Norshipco
(Berkley)
Avondale
(Main Yard)
Todd
„, (Galveston)
i— •
Jacksonville
Newport News
Lockheed
Todd
(Alameda )
NASSCO
(San Diego)
Construction/
Repair
Construction/
Repair
Repair
Repair
Construction 1,
It
Construction/
Repair
Repair
Construction
486,
306,
351,
225,
595,
484,
566,
854,
816,
188,
642,
537,
091
150
854
208
358
946
895
650
800
115
614
655
(128,954)
(80,885)
(92,960)
N/A
(59,500)
(157,294)
(123,123)
(149,774)
(490,000)
(480,000)
N/A
(49,700)
(169,779)
(142,049)
3,
2,
2,
2,
2,
22,
25,
1,
5,
6,
500
500
N/A
600
200
305
280
400
000
700
400
453
356
(79)*
(78)
(76)
(79)
(78)
(77)
(79)
(78)
(77)
(78)
(79)
139.
122.
375.
270.
210.
248.
82.
72.
470.
117.
84.
45
46
35
62
39
64
80
67
29
83
59
(36.
(32.
(99.
(71.
(55.
(65.
(21.
(19.
(124.
(31.
(22.
844)
354)
167)
497)
585)
690)
875)
20)
25)
13)
349)
*Year
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use per employee, with 90 percent confidence limits, is shown
in Table 7-2. Because of the small sample sizes involved, the
confidence limits were determined using the t-distribution with
degtees of freedom equal to one minus the sample size. The
assumption that the data represents a random sample drawn from a
near-normal population is involved.
Employment figures for all major shipyards are available for
a single year (1979) . Total major shipyard employment fov
that year was approximately 224,600. The number of shipyards
and total employment by category are also shown in Table 7-2.
VOC emissions per gallon of paint are a function of the paint
type. Data on marine coating sales and resultant emissions by
generic paint type are available for the State of California,
1976."
It. is reasonable to assume that the distribution of national
marine coating sales by generic type closely resembles the
distribution determined during this California survey (although
our visits have indicated a continuous shift to higher solid-
content paints since 1976). Therefore, the weighted average of
VOC emission per gallon of paint obtained by the CARD study,
.434 kg/liter (3.62 Ibs/gal) was used in this approach.
Estimated annual emissions, based on this analysis using data
obtained during shipyard visits, are shown in Table 7-2.
For a 250 day year the sum ot emissions from all shipyard
categories is shown to be 70.4 + 24.6 metric tons/day (77.6 +_
27.1 short tons/day) (90% confidence limits).
This estimate agrees very well with the estimate published1 in
1978 by Booz, Allen, & Hamilton inc. of 40.8 to 81.6 metric tons
(45 to 90 short tons) VOC emitted per day by ship painting
operations nationwide. This was based on 1977 data and a 250
day year.
The State of California Air Resources Board (CARB) also pub-
lished a report in 1978 based primarily on 1976 data which
estimated that 13 major California shipyards emitted 9.5
metric tons (10.5 short tons) per day of VOC. Only nine of
these yards are actually classified Code A, but assuming all of
them were and extrapolating the data to the total 76 code A
shipyards yields a national VOC emission estimate of 55.7 metric
tons (61.4 short tons) per day.
The National Paint & Coatings Association (NPCA) supplied an
estimate of sales of coatings for marine applications of
35.2 x 10b liters (9.3 x 106 gallons) in 1977. This volume is
subject to the limitations discussed in the introduction to
52
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Table 7-2
Estimated VX Qnissions from Painting at Major Shipyards
(90 Percent Confidence Limits)
Expected Value of
Paint Use No. of Total Expected \OC Omissions
per Employee Major Employment Metric
Category Llter/Yr/Sftp (GalAr/Qip) Yards (1979) Tons/Yr (Short Ton/Yr)
Construction 89.48+23.09 (23.64 + 6,10) 5 38,200 1482.84+382.66 (1,634.52+421.8)
Repair and
Construction 130.96+53.63 (34.60 + 14.17) 45 117,160 6656.39 + 2726.05 (7,337.3 + 3,004.9)
Repair 315.03 + 101.21 (83.23 + 26.74) 26 69,240 9462.73 + 3040.21 (10,430.7 + 3,351.2)
TOTAL 76 224,600 17601.95 + 6148.91 (19,402.5 + 6,777.9)
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this section but by itself translates into an emission rate of
59 metric tons (65.1 shore tons) per day + 25 percent to account
for the range of solvent volume percent in the various paints
for a 250 day year. Solvents used for cleaning and thinning are
not included ir this figure.
An individual paint formulator estimated that the entire U.S.
market for antifoulant paints was 1,892,500 liters (500,000
gallons) per year +20 percent. Using data from the CARS
report and extrapolating it to the entire U.S. population
of major shipyards yields a daily emission rate of 28.4 metric
tons (31.3 short tons) of VOC + 20 percent. This is based on a
ratio of total VOC emissions from all sources for every gallon
of antifouling paint applied. There arc obvious problems with
this approach and it should be considered the weakest: of those
utilized.
The results of all five estimation approaches are summarized in
Table 7-3. Although no single highly reliable number was
developed, the reasonable agreement of the various estimates
yields a range that can be confidently relied upon as a char-
acterization of the extent of the VOC emission problem from U.S.
ship painting operations.
54
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Table 7-3
Summary of VOC Emission Estimates
Metric Ton VOC Emitted per Day (short tons)
250 days/year 365 days/year
1. 70.4 + 24.6 (77.6 + 27.1) 1. 48.2 + 16.8 (53.2 + 18.6)
2. 40.8 to 81.6 (45 to 90) 2. 27.9 to 55.9 (30.8 to 61.6)
3. 55.7 (61.4) 3. 38.15 (42.0)
4. 59.0 + 14.8 (65.1 + 16.3) 4. 40.4 + 10.1 (44.6 + 11.2)
5. 28.4 + 5.7 (31.3 + 6.3) 5. 19.5 + 3.9 (21.4 + 4.3)
Basis of Approach
1. Employment and paint consumption based on .site visits
2. Booze, Allen, & Hamilton report
3. Extrapolation of CARB data11
4. NPCA marine paint sales
5. Ratio of VOC emissions to antifoulant use
55
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BIBLIOGRAPHY
1. Booz, Allen & Hamilton Inc., "Surface Coating in the
Ships and Boats Industry," U.S. EPA RTP, North Carolina
Sept. 1978.
?.. CENTEC Corp., "Contractor Report for che Development
of Effluent Limitation Guidelines for Paint Application
Processes Used in the Mechanical and Electrical Products
Industries," U.S. EPA, Control S68-02-2581, July 1979.
3. Curtis, Georr-o H. , "Experiences with a Sophisticated
Advanced Cleaning and Coating System," Shipcare '80 Con-
ference, Lisbon, Portugal.
4. Development Document for Proposed Effluent Limitations
Guidelines and Standards for the Shipbuilding and Repair
Point Source Category, Environmental Protection Agency,
Effluent Guidelines Division, December 1979.
5. Federation Series on Coatings Technology, Units 1-25.
Federation of Societies for Paint Technology, Philadelphia,
Pa., 1965-1978.
6. Huber, Joan E., editor, "The Kline Guide to the Paint
Industry," fifth edition, Charles H. Kline & Co.,
Fairfield, N.J., 1978.
7. Pickering, J. Robert, "Current State of Water-Borne Coating
Technology," Metal Finishing, Vol. 76, No. 1, pp. 70-74,
January 1978.
8. Principal Shipbuilding and Repair Facilities of the United
States (By Coastal Areas and Port Groupings), U.S. Depart-
ments of Defense and Commerce, Office of the Coordinator
for Ship Repair and Conversion, September 1978.
9. Report on Survey of U.S. Shipbuilding and Repair Facilities,
U.S Department of Commerce, Maritime Administration, 1S79.
10. Shreve, R. Norris, "Chemical Process Industries," third
edition, McGraw-Hill Co., N.Y., 1967.
56
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BIBLIOGRAPHY
(Continued)
11. State of California Air Resources Board, "Consideration of
a Proposed Model Rule for the Control of Volatile Organic
Compounds from Marine Coating Operations," June 29, 1978.
12. Fairbairn, Robert, "Airless Electrostatic for Aircraft,"
Finishing Industries, Vol. 4, No. 10, October 1980.
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GLOSSARY
ADDITIVES
ANTIFOULANT
BEAM
BINDERS
(RESINS)
BIOCIDES
BOOTTOP
BOOTTOPPING
CATALYST
CURING
DRYDOCK
Any substances, aside from pigment, binder/ or
solvent, introduced to influence the qualities
of paint. They include anti-skinning, anti-
sagging, anti-settling agents, preservatives,
fungicides, biocides, etc. Usually, the total
concentration will be less than 1 percent.
A chemical additive in paint that controls
marine growth on a ship's hull.
The width of a ship at its widest point.
The bulk of the film-forming ingredients which
bind or cement both the pigment particles
together and the pai-nt itself to the material
to which it is applied.
Compounds that are intended to destroy living
organisms. In paints they are considered
additives.
A paint used on the boot.topping to prevent
corrosion and fouling.
The part of a ship's hull between the light
load water line and the heavy load water
line.
A material that affects the rate of a chemical
reaction (usually by providing a reaction site)
without itself being chemically altered during
the course of the reaction.
The conversion of the paint film into a
solid layer by the use of heat, radiation,
or reaction with chemical additives.
A dock that is kept dry for use during the
construction or repairing of ships.
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DRYING OILS
EMULSIONS
FLOATING
DRYDOCK
GRAVING DOCK
HIGH SOLIDS
COATINGS
LACQUERS
LATEX PAINT
MARINE RAIL
MINERAL SPIRITS
GLOSSARY
(Continued)
Water insoluble liquids that readily absorb
oxygen fcor. the air and polymerize to form
a relatively hard, tough, elastic substance
when applied as a thin film; example: linseed
and tung oils.
Two or more immiscible liquids, generally
existing as a colloidal system, such as oil
in water, in which small droplets of one
liquid are dispersed uniformly through a
second continuous phase.
A dock that floats on water and can be partly
submerged to permit a ship to enter it and
afterward floated to raise the ship high and
dry as in a drydock.
A drydock consisting of an enclosure openly
adjoining a waterway from which it may be
separated by a watertight barrier that is
capable of being pumped dry when so sepa-
rated and which is used especially for cleaning
the underwater parts of a ship.
Liquid conventional finishes that are between
45 and 95 percent solids (by weight). The
most common application is of paint of 40
to 80 percent solids content (by weight).
A measure of the moisture content of air.
Coatings that dry primarily by evaporation
of solvent rather than by chemical reactions
between paint components and/or air.
An aqueous colloidal dispersion coating con-
taining binder (resin) particles produced
by emulsion polymerization.
Inclined tracks extending into the water so
that a ship can be hauled up on a cradle or
platform for cleaning or repairs.
F:efined petroleum distillates of low aromatic
hydrocarbon content suitable as a solvent or
thinner for paints and varnishes with boiling
points in the range 149°C to 204°C and flash
point around 27°C.
59
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OIL BASE
PAINTS
OVERSPRAY
PAINTS
PIGMENTS
PLASTICIZERS
POLYMERS
PRIMERS
RESINS
SHAVE-AHD-A-
HAIRCUT
SOLVENT
SOLVENT-BORNE
(BASE) PAINT
GLOSSARY
(Continued)
Paint containing drying oils as binders that
dry by air-induced crosslinking, where oxygen
is consumed.
Paint that misses the woirkpiece in spray
coating facilities.
Uniformly dispersed substances that are applied
in a thin layer and convert to a solid film on
the surface of a workpiece for the purpose of
protection, decoration, and/or identification.
Small, hard particles dispersed in paint that
determine its color, hue, reflectivity,
corrosion resistance, hiding power, strength,
adhesion properties, and/or viscosity, etc.
Low molecular weight liquids with high boiling
points that, when added to paint, do not
evaporate but, rather, improve its flexibility,
adhesive power, chip resistance, and form-
ability. Considered an additive.
Literally meaning many units, are long chain,
complex molecules produced by the combination
of many fairly simple molecules.
Initial surface coatings, applied to the
surface of a workpiece to provide adequate
adhesion to new surfaces or to increase the
compatability of the surface for a topcoat.
See BINDERS.
A colloquial expression used to describe the
act of blasting and painting a ship's hull.
A substance capable of dissolving another
substance, thus forming a uniformly dispersed
solution. In paint, it is the liquid, usually
volatile, that acts as the dispersion medium
for the film-forming, nonvolatile binders and
pigment and at the same time controls the
consistency of the coating, making it suitable
for application.
Coatings in which an organic liquid (solvent)
is used to disperse the binders and pigments.
60
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THERMOPLASTIC
TKERMOSETTING
THINNER
TOP COAT
(FINISH COAT)
UNDERCOAT
VM&P NAPTHA
WATER-BORNE
COATINGS
(WATER-BASED
COATINGS)
GLOSSARY
(Continued)
In this study, taken to mean the ability to be
softened by heat and to be resolidified upon
cooling.
The property of being able to undergo a chemi-
cal reaction by tho action of heat, catalyst,
or radiation that causes a substance to become
permanently hard and rigid.
A type of organic solvent that reduces the
viscosity of a paint, varnish, or lacquer
to appropriate working consistency, by having
active solvent power on the dissolved resin.
The final coating intended to bo applied to a
workpieca, usually following a primer, under-
coat, or surfaccr.
Any coating that is applied prior to the
topcoat.
Varnish Maker's and Painter's Naptha is a
fraction of petroleum distillate, consisting
of both aromacics and aliphatic hydrocarbons,
used as paint or varnish thinner with narrow
boiling point range of 93°C to 149°C and flash
point of 10°C.
A type of coating in which water acts as the
primary solvent to disperse and suspend the
pigment and binder material.
61
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