United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-96/152 January 1997
oEPA Project Summary
Finishing Fabricated Metal
Products with Powder Coating
Paul B. Kranz, James E. Stadelmaier, and Thomas F. Stanczyk
This report provides a technical and
economic evaluation of a polyester
powder coating system applied to the
exterior and interior surfaces of metal
boxes fabricated for the telephone and
cable industries. This evaluation sum-
marized many of the requirements and
benefits of a clean technology that ef-
fectively eliminates the use of hazard-
ous solvents and prevents the
generation of volatile organic emissions
and hazardous solid waste.
The technology routinely demon-
strated a system efficiency that ranged
between 95% and 98%, while providing
consistent quality under flexible work-
ing conditions.
The economic analysis resulted in a
net present value of $797,410 and a
payback period of 0.49 yr. The eco-
nomic results concur with published
references indicating labor and cleanup
costs for powder systems are about
38% lower than the costs compiled for
wet-finishing systems.
A comparative analysis of published
operating costs indicates that the pow-
der coating system is more advanta-
geous than systems using conventional
solvent, waterborne, or high-solids
coatings. The cost advantages are, in
part, attributed to lower energy and
maintenance requirements.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory, Cincinnati, OH,
to announce the key findings of the
research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
Powder coating can be simply defined
as dry paint. Instead of being dissolved or
suspended in a liquid medium, such as
solvent or water, powder is applied in its
dry form directly to the surfaces requiring
coating.
Powder coating has emerged as a clean
technology alternative to waterborne, high-
solids, and conventional solvent-based
coating systems. The commercial avail-
ability of this technology allows small and
large manufacturers to specify equipment
that can effectively accommodate variable
production schedules while attaining de-
sired quality standards.
Recent advancements in the technol-
ogy are resulting in system efficiencies
ranging between 95% and 98%. In addi-
tion to optimizing the use of costly raw
materials, a powder coating system, in
comparison with conventional wet systems,
can be operated in a manner that will
reduce labor, maintenance, and energy
costs.
From an environmental perspective,
powder coating systems have effectively
eliminated hazardous waste and releases
of toxic chemicals to air, water, and solid
media. The design features of many sys-
tems have reduced employee exposure to
any hazards posed by the use of powder
paints.
The purpose of this project was to docu-
ment and analyze the applicability and
adequacy of finishing fabricated metal
boxes with a powder coating system. The
project involved a technical and economic
assessment of the operations employed
by a small manufacturer of metal boxes
fabricated for telephone and cable indus-
tries.
The evaluation was completed under
the terms of the Erie County/EPA WRITE
Program as a joint effort by Diversified
Control, Inc., Orchard Park, NY; Erie
County Environmental Compliance Ser-
vices, Buffalo, NY; Recra Environmental,
Inc., Amherst, NY; and the U.S. Environ-
mental Protection Agency (USEPA) Office
of Research and Development, Cincinnati,
OH.
Printed on Recycled Paper
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Procedure
The industrial participant for this pro-
gram was Diversified Control, Inc. Diversi-
fied Control has been designing and
manufacturing 16-gauge steel boxes with
maximum dimensions of 24" x 24" x 8"
deep. These boxes are fabricated for use
by the telephone and cable industries. Di-
versified Control's customers require the
boxes to exceed predefined quality stan-
dards including provisions for corrosion
resistance. To meet customer require-
ments of no red rust per ASTM B117 at
1000 hr, Diversified Control is required to
pretreat surfaces before applying a paint
coating.
When during its initial years of opera-
tion, the company outsourced surface fin-
ishing and contractors employed wet
coating systems, a number of product qual-
ity problems were encountered related to
failures in salt chamber tests at 100 hr
using ASTM B117. Contractors addressed
these problems by pretreating the sur-
faces of the metal boxes with a zinc phos-
phate formulation and finished the metal
boxes with a powder coating instead of a
wet coating.
These new contracting requirements sig-
nificantly increased costs for preparing and
finishing the metal boxes per customer
specifications. Surface preparation costs
alone doubled in price.
Because of cost increases and quality
concerns, Diversified Control decided to
invest in equipment and operations that
would provide finished goods without us-
ing contractors. The factors influencing
equipment selection and operating proto-
col are addressed within the context of
this Project Summary. The company's
technical and economic assessment took
into account published references address-
ing viable techniques and requirements.
Diversified Control selected a powder
coating technology and a modular pre-
treatment system employing a zinc phos-
phate formulation. The pretreatment
system employs cleaning solutions that
were ultimately chosen after exhaustive
testing and research. The selection pro-
cess determined that the cleaning solu-
tions would not result in
A wastewater having hazardous
characteristics
A wastewater that would potentially
exceed effluent criteria governing
direct discharge into the Erie County
Sewer District
A sludge or solid residue that would
require routine maintenance and
proper disposal
Conditions that would etch the metal
boxes
To minimize the potential sources of
contamination requiring removal by the
cleaning solution, company personnel rou-
tinely monitor potential changes in stock
cleanliness originating from variations in
processing, quenching, or transportation
oils.
The selected powder coating system
was designed and manufactured by Engi-
neered Powder Applications, Inc., and the
spray guns were provided by ONODA
Ionics Division. The selection process took
into account cost, durability, commercial
availability, anticipated maintenance, and
documented performance.
To accommodate variable production
schedules, the company chose an electric
infrared (IR) oven for curing the powder
coating. To eliminate surges, which can
be encountered with a filament quartz tube
IR system, the company chose a resis-
tance IR system. PROTHERM electric in-
frared heaters, manufactured and supplied
by Process Thermal Dynamics, Inc., were
installed. These units provided the com-
pany the flexibility needed to completely
shut down the system during short idle
and off-production periods. The company
found that the electric IR system was three
times less expensive than comparable gas
systems, and to take advantage of re-
bates from the utility, the company in-
stalled additional process controls,
including electronic sensors, which auto-
matically shut off ovens during idle peri-
ods.
After the powder coating system was
installed and operational, the company in-
stalled automated laser-cutting and fabri-
cation tools as well as a robotic welding
system to accommodate increases in pro-
duction activities. These clean machines
facilitated production and further reduced
the potential for surface contamination and
scrap generation.
Figure 1 provides a schematic of flow of
operations.
Collectively, the equipment and opera-
tions cited in Figure 1 attain the desired
quality standards. To compare this sys-
tem with alternative paint coating systems,
the design specifications and operating
protocol for the powder coating system
were documented and analyzed as fol-
lows:
The company uses a quick color
change powder booth manufactured
by Engineering Powder Applica-
tions, Inc. The design specifications
for this booth are summarized in
Table 1.
The system's design allows 16-
gauge steel boxes to be conveyed
on a batch, intermittent, or continu-
ous basis from the pretreatment
system as illustrated in Figure 2.
In the first stage of the pretreat-
ment system, the initial wash em-
ploys an alkaline soap, ISW-24, a
temperate range between 140°F
and 160°F, and a pH of 9 to 9.5. A
typical retention time is 5 min.
In the second stages, metal boxes
are subjected to a rinse solution
formulated with a soap/rust inhibi-
tor to stop flash rusting. The rinse
system is operated at a tempera-
ture of 80°F and a pH of 8. A typi-
cal retention time is 1 min.
To select the most appropriate
method for applying powder coat-
ing, company personnel estimated
the square footage of material be-
ing painted per pound of paint con-
sumed. This analysis took into
account the size and geometry of
the metal boxes, the specified film
thickness, the type of coating speci-
fied for each surface, anticipated
line speed, energy requirements,
and growth in production activity.
The chosen electrostatic spray pro-
cess involves a powder feeder unit,
electrostatic powder spray guns, an
electrostatic voltage source, a pow-
der recovery unit, and a spray
booth. The process was deemed to
be the most efficient means of ap-
plying coatings in a very short pe-
riod of time, and it is conducive to
batch operations.
The company uses the GX Series
108 multimode manual spraying
guns. This multimode gun allows
the operator to choose any of three
different spraying modes without
changing equipment. (Figures 3, 4,
and 5). Multimedia gun specifica-
tions are summarized in Table 2.
Two operators use the guns to
spray the powder in the form of a
diffused cloud. The propelling force
is provided by compressed air used
to transfer the powder from the
feeder to the spray gun and by the
electrostatic charge imparted to the
powder at the gun. A source de-
signed to transmit high-voltage, low-
amperage electrical power to an
electrode attached to the spray gun
supplies the electrostatic voltage.
Figure 6 is a schematic of the end
view of the booth. As the diffused,
electrostatically charged powder
cloud nears the grounded part, an
electrical field of attraction is cre-
ated, drawing the powder particles
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fSheetmeteh
(Sheet-cutting machine)-
Unloading dock
-(Pre-defined scheduling)
Laser cutting
Robotic welding I (Box specification)
, i
Alkaline cleaning
I Spray rinse
~
Dryer
Powder
overspray
recycling
system
Powder system
1
IR ovens
2 spray guns-
paint manually
applied
Product packaging
Figure 1. Diversified Control, Inc., process flow.
Table 1. Engineered Powder Applications, Inc., Quick Color Change
Powder BoothDesign Specifications
Powder-Booth Components
Specification
Two-part openings at ends of booth
Two manual operator openings
Exhaust volume
Variable speed exhaust fan motor
Eight primary cartridge filters
Pre-filters
Final filters
Booth overall length
Compressed air
Power voltage
Control voltage
18 in. wide x 42 in. high
30 in. wide x 30 in. high
4,000 CFM
5hp
1,848 sq ft - 98% SAE J726
30% efficient ASHRAE 52-76
95% efficient ASHRAE 52-76
12ft.-0
100 psi clean, dry, no oil
480 volt/3 phase/60 Hz
120 volt/1 phase/60 Hz
to the part and creating a layer of
powder on the box surfaces.
The company uses a dry powder
paint classified as a polyester TGIC
powder coating. Typical properties
are summarized in Table 3.
The powder coating system allows
powder overspray to be recycled
into the system. The powder is
separated from the conveying air
flow in the collector unit, which al-
lows the collected powder to be
recycled back to the feeder unit.
Results and Discussion
Comparative Analysis
In the process of selecting technologies
and equipment for Diversified Control's
operations, various options were evalu-
ated based on published references. The
technical and economic analyses em-
ployed estimated requirements and costs
for installing a powder versus wet coating
system.
Based on published data provided by
vendors and the Powder Coating Institute,
the comparative analysis indicated that
Energy requirements and costs
were lower for powder coating sys-
tems.
Both powder system and a wet sys-
tem need clean, dry, oil-free com-
pressed air.
Powder booths require no water for
cleaning booth and filter media and,
typically, no natural gas to heat the
booth air.
Air used in a powder booth is typi-
cally recycled within the plant, elimi-
nating the need for stacks and air
makeup units.
A powder booth can be more ex-
pensive than a liquid booth, but a
powder booth reclaims the
oversprayed paint.
The filters used with a powder sys-
tem need to be changed only sev-
eral times a year. Unlike powder
systems, liquid systems generate
paint-saturated booth filters, which
are expensive to dispose of. A wet
booth typically does not reclaim
overspray; it contains banks of fil-
ters that can require daily chang-
ing.
With a powder system, there is no
solvent exhaust. Wet systems do
release solvent emissions, and they
require air replacement and a paint
mix room.
Spray guns used with wet systems
must be routinely cleaned; this cre-
ates additional waste quantities that
are not found with powder systems.
When compared with waterbome,
high solids, and conventional sol-
vent coating applications, the capi-
tal costs for powder systems are
slightly higher; however, pollution
control requirements for the alter-
native can make the costs for pow-
der systems advantageous.
Material costs are significantly lower
for powder systems, i.e., $2 to $37
gal versus $10 to $13/gal for sol-
vent and waterborne systems.
A powder system will use a paint
with approximately 98% solid con-
tent versus 35% to 45% solids for
solvent and waterborne systems.
Powder systems will typically yield
utilization efficiencies (actual cov-
erage sq ft/gal) ranging between
95% and 97% versus 45% and 55%
for solvent and waterborne systems.
Electrostatic liquid systems efficien-
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First floor
Deskimmer and
coalescing filter
Load/unload area
19'8
Second floor
Conveyor
Oven tunnel
Paint hopper
E
Paint booth
84'S"
227'
FlguraS. Powder paint system at Diversified Control, Inc.
Pin electrode
--"" \
Ring electrode
Figure 3. E-Mode spraying pattern of the GX Series 108 spraying gun.
(From: Ion Technologies Corporation)
cies will reportedly range between
60% and 70%. When compared
with fluid powder systems, electro-
static powder generally has a higher
deposition efficiency.
Labor costs for powder systems are
generally lower than comparable
costs for solvent and waterborne
systems.
Cleanup and maintenance costs for
powder systems are typically 50%
lower than those costs associated
with solvent and waterborne sys-
tems.
Waste quantities attributed to a
powder system are significantly
lower than the quantities generated
with solvent and waterborne sys-
tems.
Economic Analysis
Company personnel completed the fol-
lowing assessment of the benefits attrib-
uted to the purchase of new electrostatic
powder guns and a control panel.
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Inside corona charger
Figure 4. P-Mode spraying pattern of the GX Series 108 spraying gun.
(From: Ion Technologies Corporation)
Inside corona charger
Pin electrode
Figure 5. H-Mode spraying pattern of the GX Series 108 spraying gun.
(From: Ion Technologies Corporation)
Table 2. Specifications of Multimedia Gun
Mode
Gun Component
H
High Voltage Source
Gun Cable Input Voltage
Output Voltage:
- Outside Charge
- Inside Charge
Short Circuit Output Current
Weight
Gun Cable
Internal cascade built into the gun barrel
24V maximum (AC peak value)
56KV 80KV none
80KV none 80KV
160 micro amps (cutoff current set at 50 micro amp) standard
Manual gun GX108 - 755 gr (3002)
7m (23 ft) standard
Old Equipment (1989)
1,146,240 estimated sq ft being
painted/yr
33 sq ft painted/lb paint in 1989
$74,679.20 total cost of paint re-
quired with old equipment at pro-
duction levels
Proposed Method (1990)
1,146,240 estimated sq ft being
painted/yr
66.5 sq ft painted/lb paint
$37,058.91 total cost of paint re-
quired for 1 yr with new equipment
Estimated Annual Savings =
$37.620.29
Table 4 summarizes the fixed costs as-
sociated with the operations employed by
Diversified Control, Inc.
Variable costs, estimated on a daily ba-
sis from data available for a 5-mo period,
include the costs for powder paints, elec-
tricity, and labor. The compared costs were
calculated at $0.151/sq ft for powder coat-
ings and historical costs of $0.305/sq ft
for wet paint applications. The fee for con-
tracting the wet painting was $6.50/box
and is assumed to include all ancillary
costs such as disposal fees, permits, and
insurance premiums.
To accomplish the net present value
(NPV) for the project, a tax rate of 40%
was assumed along with discount factor
of 10%. The NPV for the equipment pur-
chase and installation, when added to the
NPV for operation and maintenance, pro-
vided a project cost of $123,140. This
cost is more than offset by the estimated
tax savings on depreciation and savings
on variable costs of $920,550 for a NPV
of $797,410. The payback period was cal-
culated at 0.49 yr.
Environmental Benefits
The powder coating system has elimi-
nated waste categorized as sludge, dis-
carded spray booth filters, hazardous
solvents, volatile organic emissions, and
hazardous housekeeping solids.
The pretreatment system does gener-
ate a spent solution that does not display
hazardous characteristics. Limited analy-
ses indicated the presence of zinc at el-
evated concentrations; however, the
loadings do not restrict discharge. Rinse
waters are pretreated to remove any
phase-separable oils. The resulting water
is recirculated for reuse.
Energy requirements are reduced along
with fumes emitted during operations. The
system eliminates the need for permits.
Health and Safety
Documented benefits include:
Eliminated fire hazards
Reduced in-plant emissions result-
ing in less workplace exposure
Minimized vent emissions from cur-
ing ovens
The physical and chemical properties of
TGIC polyesters must be carefully con-
trolled.
Operating Performance
The work openings provided with the
Engineered Powder Applicators, Inc., paint
booth have been sized properly allowing
for clearance of the boxes being sprayed,
ample access to boxes for manufacturing
operation, proper face velocity of air at
the opening, variable line speeds, parts
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Overhead conveyor
Roll away color module
Powder
load
chute
Integral powder
feeahopper
f
u
7
Figure 6. Schematic end view of the spray booth illustrating electrical field of attraction (From:
Engineered Powder Applicators, Inc.)
Tabta 3. Typical Properties of PolyesterTGIC Powders When UsedOvera Good Metal Pretreatment
Property Range
Hardness (pencil)
Impact (Ib)
Gloss (60* m)
Colors
Salt Spray
Condensing Humidity
Cure Range (typ. 3 mil - .07 mm)
Tima (at metal temp)
HB-H
60-160
20-90
All colors (clear and textures)
1000+ hr
1000+hr
Wmln @ 400°F(204°C)
SOmin @ 300°F(149°C)
Tabta 4. Fixed Costs for Installing the Powder Coating Technology
Unit Purchase Costs
Powdered Coating Application Booth
Protherm Curing Oven
Conveyor
Wash tanks
Powder Application Guns
Miscellaneous
Spare Parts
Piping, Electrical, Instruments, Insulation
Structural
Construction/Installation
Engineering
$ 26,000
21,000
12,000
8,000
9,000
3,000
2,000
11,000
10,000
10,000
5.000
$ 117,000
load density, and spacing oi hangers and
racks.
The design features and operating pro-
tocol of the Diversified Control system ef-
fectively achieves the desired performance
standards. Formation of good coating free
of voids, pinholes, and distortions depends
on controlling the particle size distribution,
melting point, melt viscosity, and electro-
static properties.
Conclusions
The decision by Diversified Control, Inc.,
to specify and install a powder coating
system has resulted in numerous ben-
efits, including appreciable savings attrib-
uted to reduced labor and energy costs,
increased production rates, significant cuts
in reject rates, efficient floor space re-
quirements, and reduced waste disposal
costs.
Quality conformance heavily relies on
proper surface preparation and in-plant
process control. When compared with al-
ternative coating systems, the savings
cited by Diversified Control are very ad-
vantageous and justify process expansions
that use powder applications.
The full report was submitted in fulfill-
ment of CR-816762 by Erie County De-
partment of Environment and Planning
under the sponsorship of the U.S. Envi-
ronmental Protection Agency.
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Paul B. Kranz is with Erie County Department of Environment and Planning
Division of Environmental Compliance, Buffalo, NY 14202. James E.
Stadelmaler and Thomas F. Stanczyk are with Recra Environmental, Inc.,
Amherst, NY 14228.
Paul /If. Randall is the EPA Project Officer (see below).
The complete report, entitled "Finishing Fabricated Metal Products with Powder
Coating," (Order No. PB97-125397; Cost: $21.50, subject to change) will be
available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
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EPA
PERMIT No. G-35
EPA/600/SR-96/152
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