Powder Coating as an Environmentally Acceptable 

Alternate to the System of MIL-P-53022 

and MIL-PRF-22750 

by Jeffrey L. Duncan 

ARL-TR-2965 May 2003 

Approved for public release; distribution is unlimited. 
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Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5069 

ARL-TR-2965 May 2003 

Powder Coating as an Environmentally Acceptable 

Alternate to the System of MIL-P-53022 

and MIL-PRF-22750 

Jeffrey L. Duncan 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution is unlimited. 
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1. REPORT DATE (DD-MM-YYYY)

May 2003 

2. REPORT TYPE 

Final 

3. DATES COVERED (From - To) 

May 2001 - January 2002 

5a. CONTRACT NUMBER 

5b. GRANT NUMBER 

4. TITLE AND SUBTITLE 

Powder Coating as an Environmentally Acceptable Alternate to the System of 

MIL-P-53022 and MIL-PRF-22750 

5c. PROGRAM ELEMENT NUMBER 

5d. PROJECT NUMBER 

AH84 

5e. TASK NUMBER 

6. AUTHOR(S) 

Jeffrey L. Duncan 

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7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 

U.S. Army Research Laboratory 

ATTN: AMSRL-WM-MA 

Aberdeen Proving Ground, MD 21005-5069 

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 REPORT NUMBER 

ARL-TR-2965 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) 

Albany Marine Corps Logistics Base, Maintenance Center 

ATTN: Engineering Dept., Code 882 (Mr. Steve Allen) 

814 Radford Blvd., Ste. 20325 

Albany, GA 31704-0325 

11. SPONSOR/MONITOR'S REPORT 

 NUMBER(S) 

12. DISTRIBUTION/AVAILABILITY STATEMENT 

Approved for public release; distribution is unlimited. 

13. SUPPLEMENTARY NOTES 

14. ABSTRACT 

Powder coatings offer potential performance and environmental benefits over conventional, solvent-based protective coatings. 

At the request of the Albany Marine Corps Logistics Base (MCLB), three powder coatings were evaluated as performancebased alternatives to the military specification coatings normally used on combat vehicles. Specimen panels, to which the 

powder coatings had been applied, were subjected to a selection of performance tests from MIL-P-53022, an epoxy primer 

specification, and from MIL-PRF-22750, an epoxy topcoat specification. These products are part of the U.S. Army’s Chemical 

Agent Resistant Coating (CARC) system and are applied to all Army and Marine Corps tactical equipment. These substrates, 

1020 steel with zinc phosphate pretreatment, bare aluminum, and aluminum with chromate conversion coating, were submitted, 

representing the materials from which vehicles are constructed. Coupled with the three powder coatings, that led to nine 

possible combinations of substrate and powder coating. With the exception of one minor problem, probably associated with 

substrate pretreatment rather than coating performance, all three powder coatings performed well, and the U.S. Army Research 

Laboratory believes they are acceptable for use at Albany MCLB as alternatives to the CARC specifications normally used. 

15. SUBJECT TERMS

CARC, powder coating, Albany MCLB, experimental products program, EPP 

16. SECURITY CLASSIFICATION OF: 

19a. NAME OF RESPONSIBLE PERSON

Jeffrey L. Duncan 

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410-306-0690 

Standard Form 298 (Rev. 8/98) 

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iii

Contents 

List of Figures iv

List of Tables iv

1. Background 1

2. Objective 1

3. Approach 1

4. Results 4

5. Discussion 6

6. Conclusions 7

7. References 7

Appendix. Photographs of Test Panels 9
iv

List of Figures 

Figure 1. Test panel locations where film thickness was measured. ..............................................3 

Figure A-1. Salt fog—steel substrate..............................................................................................9 

Figure A-2. Recoatability..............................................................................................................10 

Figure A-3. Flexibility—green no. 24533 on steel.......................................................................10 

Figure A-4. Flexibility—all coatings on aluminum......................................................................10 

List of Tables 

Table 1. Coatings and substrates.....................................................................................................2 

Table 2. Summary of tests and corresponding performance requirements.....................................3 

Table 3. Results for white no. 17925. .............................................................................................4 

Table 4. Results for green no. 24533. .............................................................................................5 

Table 5. Results for black no. 17038. .............................................................................................5 
1

1. Background 

In late 2000, Albany Marine Corps Logistics Base (MCLB) personnel contacted the Coatings 

Technology Team, Weapons and Materials Research Directorate, U.S. Army Research 

Laboratory (ARL) about a test program designed to approve the use of epoxy powder coatings as 

replacements for the standard chemical agent resistant coating (CARC) system used on tactical 

equipment, because ARL is the CARC Commodity Manager and the CARC approving authority 

for the Department of Defense. The powder coatings were to be used on a variety of equipment 

to replace the military specification MIL-P-53022 (1) epoxy primer and MIL-PRF-22750 (2) 

epoxy topcoat as applied to bare and pretreated aluminum and zinc phosphate pretreated steel. 

Normally, substitutions are for cases where those specifications do not meet volatile organic 

compounds (VOC) regulations in force or where new technology will provide more general 

benefits in the future or a more environmentally acceptable process for the user. Although these 

specification coatings are available in low-VOC formulations, the environmental benefits (zero 

VOC) and performance enhancements of powder coatings are well documented. The proposed 

test program and approval process fell under the auspices of ARL’s Experimental Products 

Program (EPP), which is set up to evaluate performance alternatives to military specification 

finishing systems. After discussions to set the number and type of panels required, panels were 

submitted for three powder coatings on three different substrates. 

2. Objective 

The test program was designed to evaluate epoxy powder coatings as performance-based 

alternatives to the system of epoxy primer MIL-P-53022 and epoxy topcoat MIL-PRF-22750 on 

the substrates noted in section 1. As part of a military tactical system, the parts must have CARC 

as the finishing system, and for interior components this typically includes a requirement for the 

previously mentioned specifications. For exterior use, the powder would replace only the 

primer. The powder coating needed to perform as well as or better than the system it was to 

replace. 

3. Approach 

A set of laboratory tests was assembled to evaluate the performance of the epoxy powders as a 

primer or as a combination of the primer and epoxy topcoat CARC system. While the corrosion 

resistance test requirement for salt fog exposure in MIL-P-53022 is 336 hr, the standard used in 
2

the EPP is 1000 hr, the same as for MIL-P-53084 (3), a lead and chromate free electrodeposition 

epoxy primer developed by the Coatings Technology Team. That material and its thermal curing 

process provide a much more appropriate performance standard for the powder coating process 

under consideration in this case. The supplied test panels represented the nine possible 

substrate/pretreatment/powder coating combinations envisioned by Albany MCLB and included 

the three substrates in combination with three powder coatings from the Sherwin-Williams Co. 

(Sherwin-Williams) as noted in Table 1. The white color is typical of epoxy primers in the 

CARC system, and the green and black colors are commonly used on interior surfaces of tactical 

equipment. 

Table 1. Coatings and substrates. 

Powder Coatings Substrates 

Sherwin-Williams EWS8-9004 white no. 17925 1020 steel with zinc phosphate pretreatment 

Sherwin-Williams EGS2-9007 green no. 24533 Bare aluminum 

Sherwin-Williams EBS8-9003 black no. 17038 Aluminum with chromate conversion coating 

The tests normally performed in a powder coating EPP study such as this one are extracted from 

the primer and topcoat specifications as appropriate. They are selected as laboratory simulations 

of conditions that the tactical equipment is anticipated to encounter in the field, such as exposure 

to rain, gasoline, acid rain, oil, and hydraulic fluid. However, the ultimate (and military unique) 

tests are the chemical agent resistance and resistance of the coating to Decontaminating Solution 

No. 2 (DS2). Tests run in this program and their corresponding performance requirements are 

summarized in Table 2. 

The topcoating test was modified slightly from that specified in no. 12 in Table 2, in that the 

panels were topcoated with MIL-C-53039 (4) and MIL-DTL-64159 (5), Type II. After curing, 

they were tested by crosshatch adhesion (American Society for Testing and Materials [ASTM] 

Standard D 3359 (6), Method B) and by wet tape adhesion after immersion for 24 hr in deionized 

water (FED-STD-141 (7), Method 6301). Due to the thickness of the supplied test panels, the 

mandrel flexibility test could not be performed, so the conical mandrel test in accordance with 

ASTM D 522 (8), Method A was used instead to evaluate adhesion of the powder coatings to the 

substrates. 

Prior to any testing, the dry film thickness of the powder coatings was measured. The six steel 

panels provided for the salt fog test were used, and eight measurements were made on each, 

following the pattern on Figure 1 and making a total of 48 test points for each color. The 

electronic film thickness gauge calculated the film thickness as follows: for the white no. 17925, 

the low reading was 2.05 mil, the high reading was 3.41 mil, and the average was 2.52 ± 0.25 

mil; for the green no. 24533, the low reading was 1.85 mil, the high reading was 3.20 mil, and 

the average was 2.54 ± 0.29 mil; and for the black no. 17038, the low reading was 1.91 mil, the 

high reading was 3.20 mil, and the average was 2.44 ± 0.29 mil. 
3

Table 2. Summary of tests and corresponding performance requirements. 

Test 

No. Test Reference Procedure Requirement 

1 Chemical 

agent 

resistance 

MIL-C-46168 

(9), 

para 4.3.25 

expose 5-cm2 area for 

1/2 hr 

≤40 μg of nerve agent GD and 

180 μg of mustard agent HD 

desorbed 

2 Water 

resistance 

MIL-P-53022, 

para 4.14 

immerse in water at 23 

± 1 °C (77 ± 1 °F) for 

168 hr 

initial defects, indistinguishable 

after 2 hr from unexposed film 

3 Hydrocarbon 

resistance 

MIL-P-53022, 

para 4.15 

immerse in 

hydrocarbon fluid at 23 

± 1 °C (77 ± 1 °F) for 

168 hr 

minor initial defects, 

indistinguishable after 24 hr 

from unexposed film 

4 Lube oil 

resistance 

MIL-PRF-22750, 

para 4.6.3 

immerse in lube oil at 

121 ± 3 °C (250 ± 5 °F) 

for 168 hr 

no defects after 4-hr recovery 

5 Hydraulic 

fluid 

resistance 

MIL-PRF-22750, 

para 4.6.3 

immerse in hydraulic 

fluid at 65.5 ± 3 °C 

(150 ± 5 °F) for 

168 hr 

no defects after 4-hr recovery 

6 DS2 

resistance 

MIL-C-46168, 

para 4.3.24 

expose to DS2 for 

1/2 hr 

no blistering, wrinkling, or film 

softening, ∆ENBS ≤2.5 units 

7 Acid 

resistance 

MIL-C-46168, 

para 4.3.21 

expose to 10% acetic 

acid for 1 hr 

no blistering and no change from 

the original color 

8 Color FED-STD-595 

(10) 

compare to standard 

color chip 

visual match 

9 Gloss 

(60° and 85°) 

ASTM D 523 

(11) 

instrumental 

measurement 

color dependent 

10 Crosshatch 

adhesion 

ASTM D 3359 see ASTM 3359 rating 4B or better 

11 Flexibility MIL-P-53022, 

para 4.13 

1/4-in mandrel bend no cracking or flaking 

12 Intercoat 

adhesion 

MIL-P-53022, 

para 4.17 

apply CARC topcoat no attack on primer, difficult to 

remove 

13 Salt fog 

resistance 

ASTM B 117 

(12) 

1000-hr exposure to 

ASTM B 117 method 

no more than 5 scattered blisters 

≤1 mm in diameter 

Figure 1. Test panel locations where film thickness 

was measured. 
4

While most measurements fell within a typical range of 2–3.5 mil, several had either thinner or 

thicker films. Where film thickness was an important factor in a test (i.e., flexibility), every 

effort was made to use a panel with the typical (assumed to be production) film thickness. 

Where film thickness was not as important (e.g., DS2 or acid resistance), the most appropriate 

panel was selected. 

4. Results 

Test results are summarized in Tables 3–5. In general, the “resistance” testing was satisfactory, 

but there were minor problems with flexibility. Photographs of some of the test panels are 

included in the Appendix. 

Table 3. Results for white no. 17925. 

Substrate Test Pretreated Steel Bare Aluminum Pretreated Aluminum 

Color no. 17925 Passa — — 

Gloss (60°/85°) 97.5 / 96.4b — — 

Flexibility Pass Pass Pass 

Crosshatch adhesion Pass (5B) Pass (4B) Pass (5B) 

Acid resistance Pass Pass Pass 

Water resistance Pass Pass Pass 

Hydrocarbon resistance Pass Pass Pass 

Lube oil resistance Pass Pass Pass 

Hydraulic fluid resistance Pass Pass Pass 

DS2 resistance Pass Pass Pass 

Chemical agent resistance Pass — — 

Intercoat dry adhesion (53039) — Pass (5B) — 

Intercoat dry adhesion (64159) — Pass (4B) — 

Intercoat wet adhesion (53039) — Pass — 

Intercoat wet adhesion (64159) — Pass — 

Salt fog—scored Pass Pass Pass 

Salt fog—unscored Pass Pass Pass a

Customer decision on acceptability; however, good visual match, and instrumentally determined as ∆ENBS ~0.5 units 

when compared to the FED-STD-595, color no. 17925 chip. 

b

Customer decision on acceptability. 
5

Table 4. Results for green no. 24533. 

Substrate Test Pretreated Steel Bare Aluminum Pretreated Aluminum 

Color no. 24533 Passa — — 

Gloss (60°/85°) 21.6/49.6b — — 

Flexibility Passc Pass Pass 

Crosshatch adhesion Pass (5B) Pass (5B) Pass (5B) 

Acid resistance Pass Pass Pass 

Water resistance Pass Pass Pass 

Hydrocarbon resistance Pass Pass Pass 

Lube oil resistance Pass Pass Pass 

Hydraulic fluid resistance Pass Pass Pass 

DS2 resistance Pass Pass Pass 

Chemical agent resistance Pass — — 

Intercoat dry adhesion (53039) — Pass (5B) — 

Intercoat dry adhesion (64159) — Pass (4B) — 

Intercoat wet adhesion (53039) — Pass — 

Intercoat wet adhesion (64159) — Pass — 

Salt fog—scored Pass Pass Pass 

Salt fog—unscored Pass Pass Pass 

a

Customer decision on acceptability; however, good visual match, and instrumentally determined as ∆ENBS ~1.75 

units when compared to the FED-STD-595, color no. 24533 chip. 

b

Customer decision on acceptability. 

c

Some delamination at small radius bend (see section 5; Figure A-3). 

Table 5. Results for black no. 17038. 

Substrate Test Pretreated Steel Bare Aluminum Pretreated Aluminum 

Color no. 17038 Passa — — 

Gloss (60°/85°) 97.3/96.2b — — 

Flexibility Pass Pass Pass 

Crosshatch adhesion Pass (5B) Pass (4B) Pass (5B) 

Acid resistance Pass Pass Pass 

Water resistance Pass Pass Pass 

Hydrocarbon resistance Pass Pass Pass 

Lube oil resistance Pass Pass Pass 

Hydraulic fluid resistance Pass Pass Pass 

DS2 resistance Pass Pass Pass 

Chemical agent resistance Pass — — 

Intercoat dry adhesion (53039) — Pass (5B) — 

Intercoat dry adhesion (64159) — Pass (4B) — 

Intercoat wet adhesion (53039) — Pass — 

Intercoat wet adhesion (64159) — Pass — 

Salt fog—scored Pass Pass Pass 

Salt fog—unscored Pass Pass Pass 

a

Customer decision on acceptability; however, good visual match, and instrumentally determined as ∆ENBS ~1.79 

units when compared to the FED-STD-595, color no. 17038 chip. 

b

Customer decision on acceptability. 
6

5. Discussion 

The ultimate criterion for a CARC substitute is its chemical agent resistance, and the results from 

the U.S. Army Edgewood Chemical and Biological Center for all three powder coatings were 

excellent with readings of less than 10-μg HD (mustard agent) on each test panel. The test for 

GD (nerve agent) is under revision and was not run. All three also showed acceptable resistance 

to DS2 exposure, with minimal color changes and no softening, indicating that decontamination 

of surfaces exposed to chemical warfare agents would not adversely affect the materials. 

Adhesion of each powder coating to the three substrates was excellent. The purpose of the 

topcoating (intercoat adhesion) test, with the subsequent crosshatch and wet tape adhesion tests, 

was to validate the ability to topcoat the powder used as a primer or to repair or rework powder 

coated items later. Even at the high gloss levels obtained for the white and black submissions, 

the results were excellent. Resistance to exposure to water, acid, hydrocarbon fluid, hydraulic 

fluid, and lubricating oil was excellent, typical of a quality epoxy coating. All three of the 

powder coatings performed very well in the corrosion resistance (salt fog) test. The aluminum 

substrate had little score corrosion and only a few defects elsewhere after 1008-hr exposure. The 

steel exhibited some score corrosion, but with minimal undercutting, and also had few defects 

elsewhere. 

As previously indicated, the thickness of the test panels precluded using the mandrel flexibility 

test method specified in MIL-P-53022 and normally used in powder coating EPP testing. 

Instead, the conical mandrel flexibility test (ASTM D 522, Method A) was used. The only 

defect noted was for the sea foam green color on the pretreated steel substrate. There, 

delamination was noted for a diameter up to ~1/2 in. The test was performed on three different 

panels with dry film thicknesses of ~1.53, 2.25, and 3.09 mil. Since the flexibility was 

acceptable for the other two substrates, the problem likely lies with the surface preparation and 

not with the powder coating. However, this would indicate that the pretreatment process and the 

dry film thickness must be closely monitored until satisfactory flexibility is obtained. Visual 

appearance and instrumental determination of color difference between the samples and the 

FED-STD-595 samples were acceptable, but color acceptability is usually a customer decision. 

Also, as previously indicated, while all three colors performed well in the corrosion resistance 

test and would therefore perform acceptably as primers, when a CARC topcoat is applied, the 

infrared reflectance of the system could be affected and the camouflage properties compromised 

by the black or sea foam green colors, and solar heat loading could be increased. 
7

6. Conclusions 

The only problem noted in this study was the delamination noted during the flexibility test for 

the sea foam green color on the pretreated steel substrate. Since this is likely a pretreatment 

problem rather than a problem with the powder coating, ARL believes that all three SherwinWilliams products tested in this project are acceptable for use as substitutes in the CARC system. 

It is, of course, the user’s responsibility to monitor the surface preparation, application, and 

curing processes to ensure satisfactory results in a production environment. The three powder 

coatings are Sherwin-Williams product EWS8-9004 white no. 17925, EGS2-9007 sea foam 

green no. 24533, and EBS8-9003 black no. 17038. 

7. References 

1. MIL-P-53022. Primer, Epoxy Coating, Corrosion Inhibiting, Lead and Chromate Free

1988. 

2. MIL-PRF-22750. Coating, Epoxy, High-Solids 1994.

3. MIL-P-53084. Primer, Cathodic Electrodeposition, Chemical Agent Resistant 1994. 

4. MIL-C-53039. Coating, Aliphatic Polyurethane, Single Component, Chemical Agent 

Resistant 1993. 

5. MIL-DTL-64159. Coating, Water Dispersible Aliphatic Polyurethane, Chemical Agent 

Resistant 2002. 

6. ASTM D 3359. Standard Test Methods for Measuring Adhesion by Tape Test. Annu. Book 

ASTM Stand. 2002.

7. FED-STD-141. Paint, Varnish, Lacquer, and Related Materials: Methods of Inspection, 

Sampling, and Testing 2001. 

8. ASTM D 522. Standard Test Methods for Mandrel Bend Test of Attached Organic 

Coatings. Annu. Book ASTM Stand. 2001. 

9. MIL-C-46168. Coating, Aliphatic Polyurethane, Chemical Agent Resistant 1993. 

10. FED-STD-595. Colors Used in Government Procurement 1994. 

11. ASTM D 523. Standard Test Method for Specular Gloss. Annu. Book ASTM Stand. 1999. 
8

12. ASTM B 117. Standard Practice for Operating Salt Spray (Fog) Apparatus. Annu. Book 

ASTM Stand. 2002. 
9

Appendix. Photographs of Test Panels 

Figure A-1. Salt fog—steel substrate.
10

Figure A-2. Recoatability. 

Figure A-3. Flexibility—green no. 24533 on steel. 

Figure A-4. Flexibility—all coatings on aluminum. 
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