United States National Risk Management

Environmental Protection Research Laboratory

Agency Cincinnati, OH 45268

Research and Development EPA/600/SR-96/152 January 1997

Finishing Fabricated Metal

Products with Powder Coating

Paul B. Kranz, James E. Stadelmaier, and Thomas F. Stanczyk

Project Summary

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 summarized many of the requirements and

benefits of a clean technology that effectively eliminates the use of hazardous solvents and prevents the

generation of volatile organic emissions

and hazardous solid waste.

The technology routinely demonstrated a system efficiency that ranged

between 95% and 98%, while providing

consistent quality under flexible working conditions.

The economic analysis resulted in a

net present value of $797,410 and a

payback period of 0.49 yr. The economic 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 powder coating system is more advantageous 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 documented in a separate report of the same

title (see Project Report ordering information 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, highsolids, and conventional solvent-based

coating systems. The commercial availability of this technology allows small and

large manufacturers to specify equipment

that can effectively accommodate variable

production schedules while attaining desired quality standards.

Recent advancements in the technology are resulting in system efficiencies

ranging between 95% and 98%. In addition 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 systems have reduced employee exposure to

any hazards posed by the use of powder

paints.

The purpose of this project was to document 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 industries.

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 Services, Buffalo, NY; Recra Environmental,

Inc., Amherst, NY; and the U.S. Environmental Protection Agency (USEPA) Office

of Research and Development, Cincinnati,

OH.
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Procedure

The industrial participant for this program was Diversified Control, Inc. Diversified 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. Diversified Control’s customers require the

boxes to exceed predefined quality standards including provisions for corrosion

resistance. To meet customer requirements 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 operation, the company outsourced surface finishing and contractors employed wet

coating systems, a number of product quality problems were encountered related to

failures in salt chamber tests at 100 hr

using ASTM B117. Contractors addressed

these problems by pretreating the surfaces of the metal boxes with a zinc phosphate formulation and finished the metal

boxes with a powder coating instead of a

wet coating.

These new contracting requirements significantly 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 using contractors. The factors influencing

equipment selection and operating protocol are addressed within the context of

this Project Summary. The company’s

technical and economic assessment took

into account published references addressing viable techniques and requirements.

Diversified Control selected a powder

coating technology and a modular pretreatment system employing a zinc phosphate formulation. The pretreatment

system employs cleaning solutions that

were ultimately chosen after exhaustive

testing and research. The selection process determined that the cleaning solutions 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 routinely 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 Engineered 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 resistance IR system. PROTHERM electric infrared heaters, manufactured and supplied

by Process Thermal Dynamics, Inc., were

installed. These units provided the company 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 rebates from the utility, the company installed additional process controls,

including electronic sensors, which automatically shut off ovens during idle periods.

After the powder coating system was

installed and operational, the company installed automated laser-cutting and fabrication tools as well as a robotic welding

system to accommodate increases in production 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 operations cited in Figure 1 attain the desired

quality standards. To compare this system with alternative paint coating systems,

the design specifications and operating

protocol for the powder coating system

were documented and analyzed as follows:

• The company uses a quick color

change powder booth manufactured

by Engineering Powder Applications, 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 continuous basis from the pretreatment

system as illustrated in Figure 2.

• In the first stage of the pretreatment system, the initial wash employs 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 inhibitor to stop flash rusting. The rinse

system is operated at a temperature of 80°F and a pH of 8. A typical retention time is 1 min.

• To select the most appropriate

method for applying powder coating, company personnel estimated

the square footage of material being painted per pound of paint consumed. This analysis took into

account the size and geometry of

the metal boxes, the specified film

thickness, the type of coating specified for each surface, anticipated

line speed, energy requirements,

and growth in production activity.

The chosen electrostatic spray process involves a powder feeder unit,

electrostatic powder spray guns, an

electrostatic voltage source, a powder recovery unit, and a spray

booth. The process was deemed to

be the most efficient means of applying coatings in a very short period 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 specifications 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 designed to transmit high-voltage, lowamperage 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 created, drawing the powder particles
3

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 alFigure 1. Diversified Control, Inc., process flow.

Table 1. Engineered Powder Applications, Inc., Quick Color Change

Powder Booth—Design Specifications

Powder-Booth Components Specification

Two-part openings at ends of booth 18 in. wide x 42 in. high

Two manual operator openings 30 in. wide x 30 in. high

Exhaust volume 4,000 CFM

Variable speed exhaust fan motor 5 hp

Eight primary cartridge filters 1,848 sq ft - 98% SAE J726

Pre-filters 30% efficient ASHRAE 52-76

Final filters 95% efficient ASHRAE 52-76

Booth overall length 12 ft. - 0

Compressed air 100 psi clean, dry, no oil

Power voltage 480 volt/3 phase/60 Hz

Control voltage 120 volt/1 phase/60 Hz

Unloading dock

Laser cutting

Robotic welding

Alkaline cleaning

Spray rinse

Dryer

Powder system

IR ovens

Product packaging

(Box specification)

Sheet-cutting machine

Sheet metal

Pre-defined scheduling

Powder

overspray

recycling

system

2 spray guns--

paint manually

applied

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 evaluated based on published references. The

technical and economic analyses employed 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 systems.

• Both powder system and a wet system need clean, dry, oil-free compressed 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 typically recycled within the plant, eliminating the need for stacks and air

makeup units.

• A powder booth can be more expensive than a liquid booth, but a

powder booth reclaims the

oversprayed paint.

• The filters used with a powder system need to be changed only several 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 filters that can require daily changing.

• 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 creates additional waste quantities that

are not found with powder systems.

• When compared with waterborne,

high solids, and conventional solvent coating applications, the capital costs for powder systems are

slightly higher; however, pollution

control requirements for the alternative can make the costs for powder systems advantageous.

• Material costs are significantly lower

for powder systems, i.e., $2 to $3/

gal versus $10 to $13/gal for solvent and waterborne systems.

• A powder system will use a paint

with approximately 98% solid content versus 35% to 45% solids for

solvent and waterborne systems.

• Powder systems will typically yield

utilization efficiencies (actual coverage 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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Conveyor

Dryer

Wash tank

Wash storage tank

Dl rinse tank Deskimmer and

coalescing filter

19'8"

29'5"

Load/unload area

First floor

Paint booth

Paint hopper

84'5"

22'7"

Conveyor

Oven tunnel

Primary oven

Second floor

Figure 2. 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, electrostatic 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 systems.

• Waste quantities attributed to a

powder system are significantly

lower than the quantities generated

with solvent and waterborne systems.

Economic Analysis

Company personnel completed the following assessment of the benefits attributed to the purchase of new electrostatic

powder guns and a control panel.
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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 required with old equipment at production 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 required for 1 yr with new equipment

Estimated Annual Savings =

$37,620.29

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 4 summarizes the fixed costs associated with the operations employed by

Diversified Control, Inc.

Variable costs, estimated on a daily basis from data available for a 5-mo period,

include the costs for powder paints, electricity, and labor. The compared costs were

calculated at $0.151/sq ft for powder coatings and historical costs of $0.305/sq ft

for wet paint applications. The fee for contracting 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 purchase and installation, when added to the

NPV for operation and maintenance, provided 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 calculated at 0.49 yr.

Environmental Benefits

The powder coating system has eliminated waste categorized as sludge, discarded spray booth filters, hazardous

solvents, volatile organic emissions, and

hazardous housekeeping solids.

The pretreatment system does generate a spent solution that does not display

hazardous characteristics. Limited analyses indicated the presence of zinc at elevated 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 resulting in less workplace exposure

• Minimized vent emissions from curing ovens

The physical and chemical properties of

TGIC polyesters must be carefully controlled.

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

Table 2. Specifications of Multimedia Gun

Mode

Gun Component H E P

High Voltage Source Internal cascade built into the gun barrel

Gun Cable Input Voltage 24V maximum (AC peak value)

Output Voltage:

- Outside Charge 56KV 80KV none

- Inside Charge 80KV none 80KV

Short Circuit Output Current 160 micro amps (cutoff current set at 50 micro amp) standard

Weight Manual gun GX108 - 755 gr (3002)

Gun Cable 7 m (23 ft) standard
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Roll away color module

Powder

load

chute

Integral powder

feed hopper

Overhead conveyor

Figure 6. Schematic end view of the spray booth illustrating electrical field of attraction (From:

Engineered Powder Applicators, Inc.)

Table 3. Typical Properties of Polyester TGIC Powders When Used Over a Good Metal Pretreatment

Property Range

Hardness (pencil) HB-H

Impact (lb) 60-160

Gloss (60° m) 20-90

Colors All colors (clear and textures)

Salt Spray 1000+ hr

Condensing Humidity 1000+ hr

Cure Range (typ. 3 mil - .07 mm) 10 min @ 400°F (204°C)

Time (at metal temp) 30 min @ 300°F (149°C)

load density, and spacing of hangers and

racks.

The design features and operating protocol of the Diversified Control system effectively 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 electrostatic properties.

Conclusions

The decision by Diversified Control, Inc.,

to specify and install a powder coating

system has resulted in numerous benefits, including appreciable savings attributed to reduced labor and energy costs,

increased production rates, significant cuts

in reject rates, efficient floor space requirements, and reduced waste disposal

costs.

Quality conformance heavily relies on

proper surface preparation and in-plant

process control. When compared with alternative coating systems, the savings

cited by Diversified Control are very advantageous and justify process expansions

that use powder applications.

The full report was submitted in fulfillment of CR-816762 by Erie County Department of Environment and Planning

under the sponsorship of the U.S. Environmental Protection Agency.

Table 4. Fixed Costs for Installing the Powder Coating Technology

Unit Purchase Costs

Powdered Coating Application Booth $ 26,000

Protherm Curing Oven 21,000

Conveyor 12,000

Wash tanks 8,000

Powder Application Guns 9,000

Miscellaneous 3,000

Spare Parts 2,000

Piping, Electrical, Instruments, Insulation 11,000

Structural 10,000

Construction/Installation 10,000

Engineering 5,000

$ 117,000
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United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

Official Business

Penalty for Private Use

$300

EPA/600/SR-96/152

Paul B. Kranz is with Erie County Department of Environment and Planning

Division of Environmental Compliance, Buffalo, NY 14202. James E.

Stadelmaier and Thomas F. Stanczyk are with Recra Environmental, Inc.,

Amherst, NY 14228.

Paul M. 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