The Evaluation of Supercritical CO, 

Application of CARC 

by Jeffrey Duncan, Donovan Harris, 

and Christopher Miller 

September 2000 

Approved for public release; distribution is unlimited. 
The findings in this report are not to be construed as an official 

Department of the Army position unless so designated by other 

authorized documents. 

Citation of manufacturer’s or trade names does not constitute an 

official endorsement or approval of the use thereof. 

Destroy this report when it is no longer needed. Do not return 

it to the originator. 

c I 

. 
Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5069 

ARL-l-R-2339 September 2000 

The Evaluation of Supercritical 

CO, Application of CARC 

Jeffrey Duncan, Donovan Harris, 

and Christopher Miller 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution is unlimited. 
Abstract 

At the request of the U.S. Army Tank-automotive and Armaments Command (TACOM), 

the Coating Technologies Team of the U.S. Army Research Laboratory (ARL), Weapons 

and Materials Research Directorate (WMRD), evaluated a chemical-agent resistant 

coating (CARC) reformulated to be compatible with the supercritical Co, application 

process. Test panels were prepared by the Concurrent Technologies Corporation (CTC) 

and submitted to ARL’s Experimental Products Program (EPP) for approval. Thus far, 

four different and separate formulations have been submitted, and all have failed, 

including the fourth and most recent submission prepared at the CTC on 12 November 

1999. In each case, excessive voids and pinholes riddled the coating film applied with 

supercritical co,. To date, the use of supercritical Co, has not been successful in 

demonstrating its ability to apply ‘CARCs free of voids or pinholes. This report 

summarizes the test program and the results through 24 November 1999. 
Table of Contents 

Page 

1. 

2. 

3. 

4. 

List of Figures .......................................................................................................... V 

List of Tables ........................................................................................................... vii 

Background ............................................................................................................... 1 

Test Procedures ....................................................................................................... 2 

Test Results .............................................................................................................. 4 

Discussion ................................................................................................................. 15 

5. 

6. 

Conclusion ................................................................................................................ 15 

References ................................................................................................................ 17 

Distribution List ...................................................................................................... 19 

R&port Documentation Page ................................................................................... 21 

. . . 

111 
INTEN??ONALLY LEFT BLANK. 

iv 
Figure 

1. 

2. 

3. 

4. 

5. 

List of Figures 

Page 

Salt Fog Blistering Results . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

Salt Fog Creep Results ........................................................................................... 10 

GM 9540P Perfornmce Results ............................................................................. 12 

GM 9540P Creep Evaluation Results ...................................................................... 12 

Black and White Images ......................................................................................... 14 

V 
bJTENTIONALLY LEfl BLANK. 

vi 
List of Tables 

Table Pape 

1. Coatings Descriptions ............................................................................................ 2 

2. Panel Tests, 4-in x 12% Size ................................................................................. 3 

3. Panel Tests, 4-in x &in Size ................................................................................... 4 

4. 4-in x 12-in Panel Dry-Film Thicknesses (mil) ........................................................ 5 

5. 4-in x 6-in Panel Dry-Film Thicknesses (mil) .......................................................... 6 

6. UNICARB Test Result Summary ........................................................................... 7 

7. Accelerated Weathering Color Differences (AENBS) ............................................. 8 

Vii 
INTENTIONALLY LEFT BLANK. 

1.. 

VI11 
. 

1. Background 

For several years, TACOM has been interested in reducing the volatile organic compound 

(VOC) content of the U.S. Army’s chemical-agent-resistant coating (CARC) by using 

supercritical CO:! for spray application. This application process, marketed by Union Carbide 

under the patented UNICARB designation, requires reformulation of a standard coating for 

compatibility with supercritical CO2 reduction. The U.S. Army Research Laboratory’s (ARL) 

Coatings Technologies Team became involved because it is the activity responsible for CARC, 

including research and development (R&D), specification preparation, and the generation and 

maintenance of any associated qualified products list (QPL). The major concern was whether or 

not the supercritical CO2 application process or the reformulation necessary would affect the 

performance of the applied coating. In addition, this change in composition itself is in direct 

conflict with the qualification process as governed by SD-6 [ 11, Provisions Governing 

Qualification (QPL). 

Because the reformulated coatings do not meet specification composition requirements, the 

mechanism for evaluating them is the Experimental Products Program (EPP), set up by ARL to 

investigate performance-based alternatives to specification materials. It allows evaluation of 

products offering the Army benefits not mentioned by these specifications, such as improved 

performance or environmental acceptability. The set of tests used to evaluate the applied films 

was extracted from appropriate material specifications. In addition, photographic procedures 

were used to objectively demonstrate the film voids and pinholes in the supercritical CO2 

samples. Test panels for this program were prepared by the National Defense Center for 

Environmental Excellence (NDCEE) a part of the Concurrent Technologies Corporation, using a 

statement of work (SOW) developed mutually by the U.S. Army Tank-automotive and 

Armaments Command (TACOMJ and ARL. The basic intent was to investigate the two 

potential problem areas previously mentioned: reformulation and application. The SOW called 

for test panels to be prepared using standard CARC applied both conventionally and via the 

suPercritical CO2 application process, along with reformulated CARC applied both 

conventionally and via the supercritical CO2 application process. TACOM later added a fifth set 

1 
of test panels, a reformulated lower-VOC CARC, applied via the supercritical CO2 application 

process. The SOW called for a total of 25 panels to be prepared in each set, allowing for all of 

the EPP performance testing, and several extras in case of problems or a desire to repeat a 

particular test. The substrate of choice was 4-in x 12-in zinc phosphate-pretreated steel (TT-C490, Type 1) with 1 mil of epoxy primer in accordance with ML-P-53022 [2]. In addition, five 

phosphoric acid-etched panels for each set were prepared from thin steel (31 gauge) for 

flexibility testing. Hentzen Coatings, Inc. manufactured the topcoats. This report summarizes 

the test program and its results. 

2. Test Procedures 

As previously noted, since the panels were prepared by the NDCEE, the EPP testing focused 

on the performance of the cured dry films. Hentzen manufacturing codes and formulation data 

for the five sets of panels are listed in Table 1. 

Upon delivery, the test panels were arbitrarily assigned to specific tests on the basis of the 

panel label. Tables 2 and 3 show the labels on the panels and the test for each. 

Table 1. Coatings Descriptions 

Set Manufacturer’s Code Application Method Description 

(no./gal VOC) 

A 08605GUZ-GD Supercritical CO2 3.5 

B RLE14697GUZ Supercritical CO2 2.8 

II I C RwE15147GUZ I Supercritical CO2 I 2.2 I 

D 08605GUZ-GD Conventional 3.5 

E RLE14697GUZ Conventional 2.8 (thinned for spray) . 

2 
Table 2. Panel Tests, 4-in x 12-in Size 

11 Sequence No. 1 be1 

7-i D E 

.l‘est 

A B C 

II 1 119 1 1 1 Chemical-agent resistance 

2 1 2 1 Gloss, color, IR, DS2 resistance, acid resistance 

3 1 3 I Recoat with MIL-C-46168 [3] 

-oatwith MIL-C-53039 [4] 

5 1 51 Recoat with MIL-P-64159 [5] II 

616~~O%stance, HC resistance 6 I 6 II 

71-l- 7 Lube T oil resistance, hydraulic fluid resistance II 

8 I 8 8 8 Xenon-arc weathering 

9 9 Xenon-arc weathering 

10 10 QUV weathering 

11 11 QUV weathering 

12 12 Outdoor exposure 

13 13 EMMAQUA 

14 14 EMMAQUA 

15 15 Wet/dry adhesion 

16 16 (not assigned) 

17 17 (not assigned) 

10 I 10 

II 11 1 11 I 11 I 19 

lr- 12 1 17 1 12 1 20 

II 13 1 18 1 13 1 21 

II 14 1 19 I 14 I 22 

II 17 1 24 1 17 1 25 

11 18 1 25 1 18 1 26 18 1 18 1 ASTM B117 [6] II 

II 19 1 26 1 19 1 27 19 19 ASTM B117 [6] 

20 20 ASTMB117 [6] 

21 21 ASTMB117 [6] 

22 22 GM 9540P [7] 

23 23 GM 9540P [7] 

24 24 GM 9540P [7] 

ir- i0 127 120 128 

II 21 I28 I21 I29 

22 29 22 30 

23 30 23 31 

11 24 I31 I24 I32 

II 25 I32 I39 I39 

3 
Table 3. Panel Tests, 4-in x Gin Size 

Sequence No. Panel Label Test 

A B C D E 

3. Test Results 

Prior to performing any tests, dry-film thickness measurements were performed on all of the 

submitted test panels. Results for the 4-in x 12-in panels are shown in Table 4, and the results 

for the 4-m x 6-in panels are shown in Table 5. 

The measurements listed in Tables 4 and 5 are averages of eight readings taken per panel, 

and the format indicates the standard deviation as calculated by the Elcometer dry-film thickness 

gauge (ie., 3.95/0.15 indicates an average film thickness of 3.95 + 0.15 mil). 

Primed panels without topcoat were also prepared by the NDCEE. Dry-b thickness 

measurements indicated that the primer was applied (average of four panels measured) at a 

dry-film thickness of 1.02/O. 11 mil. Using this number, the film thickness of the topcoat can be 

estimated to be approximately 3 mil for series A, B, C, and E. The topcoat for series D was 

thinner, about 2.5 mil. 

Performance test results were acceptable in most cases. ARL sent preliminary test results to 

TACOM in early June 1999. Because of problems with the spectrophotometer used to measure 

color and infrared (JR) reflectance, it was not possible at that point to calculate the color changes 

4 
Table 4. 4-in x 12.in Panel Dry-Film Thicknesses (mil) 

“Sequ~ce no. 1 panels were submitted for chemical-agent resistance testing prior to making the Clm 

thickness measurements. 

, 

due to accelerated weathering. In addition, the longer-term corrosion resistance testing was not 

yet complete. Since then, all testing has been completed, and the interim results can be updated. 

They are summarized in Table 6. Where appropriate, an elaboration on the test results is 

provided. 

5 
Table 5. 4-h x 6-h Panel Dry-Film Thicknesses (mil) 

Chemical-agent resistance was performed per paragraph 4.3.24 of MlL-C-53039 [4]. Results 

for two panels each series are complete, and the averages (in micrograms desorbed) for series A 

through E, respectively, are 40,150, 10, 110, and 135. The allowable limit is 180. 

Testing for color, gloss, IR reflectance, DS2 resistance, acid resistance, recoatability with 

ML-C-46168 [3], recoatability with MLC-53039 [4], recoatability with ML-P-64159 [5] (the 

proposed new specification for water-dispersible CARC), Hz0 resistance, and HC resistance 

were done in accordance with the appropriate paragraphs in MIL-C-53039 [4]. This testing was 

essentially “pass/fail,” and all results were acceptable. Testing for lubricating oil resistance and 

hydraulic fluid resistance was performed in accordance with the appropriate paragraphs in 

ML-PRF-22750 [8]. Again, all results were acceptable. 

Xenon-arc accelerated weathering was performed in accordance with American Society for 

Testing and Materials (ASTM) Standard G26 [9] in increments of 300 hr in a controlled 

irradiance Atlas Weatherometer. Color changes (an average of four panels exposed) after the 

first 300 hr, the specification requirement, were acceptable. The exposure has been continued 

for additional increments of 300 hr, and color changes at 600 hr and 900 hr are shown in Table 7. 

QUV accelerated weathering was performed in accordance with ASTM G53 [lo] for 500 hr 

in a Q Panel machine. Color changes (an average of four panels exposed) after 500 hr were 

acceptable. The exposure has been continued for additional increments of 500 hr, and color 

changes at 1,000 hr and 1,500 hr are shown in Table 7. 
Table 6. UNICARB Test Result Summary 

Panel Series 

Test 

A B C D E 

Chemical-Agent Pass fail Pass PUS Pass 

Resistance 

Gloss Pass Pas pass Pa= Pass 

Color Pass pass pass Pas Pa= 

IR Pa= pass Pass Pas Pas 

l/4+ Mandrel Pass pass pass Pa= Pa= 

Flexibility 

Spraying Properties fail fail fail Pas Pa= 

DS2 Resistance pass Pas pass Pa= Pass 

Acid Resistance Pa= Pass pass Pa= Pa= 

Recoatability Pa= pass pass Pa= Pass 

Water Resistance Pa= Pa= pass Pass Pass 

Hydrocarbon Pa= Pa= pass Pa= Pa= 

Resistance 

Lube Oil Resistance Pass pass Pass Pa= Pass 

Hydraulic Fluid Pa= Pa= pass Pas Pass 

Resistance 

Xenon Accelerated pass pass pass Pass Pa= 

Weathering 

QUV Accelerated pass pass pass Pa= Pa= 

Weathering 

Outdoor Exposure in progress in progress in progress in progress in progress 

EMMAQUA in progress in progress in progress in progress in progress 

ASTM B117 [6] -. -8 -8 -* -* 

Salt Fog Exposure 

GM954OP 

Acceletited -. -’ -* -. -* 

Corrosion 

Film Porosity fail fail fail Pa= pass 

^^ lx-.-n * A 

7 
Table 7. Accelerated Weathering Color Differences (AENBS) 

Although corrosion-resistance testing is generally not a topcoat test requirement, these tests 

were run to determine total system performance in both the standard ASTM B 117 [6] salt fog 

exposure and in the GM 954OP [7] cyclic corrosion tests. 

Twenty panels, four replicates for each of the five coating processes, were provided for 

ASTM B117 [6] testing. The lower half of two panels from each set were scribed with an X that 

covered the area. After the backs and edges were coated with beeswax, panels were exposed to 

5% salt fog for 1,000 hr (-6 wk). Evaluations were performed using ASTM D1654 [ 1 l] 

procedure A for creep from scribe (direct measurements were done in millimeters, not the l-10 

scale provided, where 10 is the best) and ASTM D714 [12] for blistering. The creep from scribe, 

measured at the point of greatest creep, ranged from 3.75 mm for series C to 5.75 mm for series 

E, after 1,000 hr of exposure. This corresponds to ASTM D714 [12] ratings ranging from 5 to 4. 

The criterion for passing is a rating of 7 after 336 hr. Nearly all of the panels had blisters in the 

unscribed areas. Blisters in the scribed areas were ignored for this evaluation. Series A and 

series C each had one panel out of four that only had a few small blisters. The remaining panels 

exhibited varying degrees of poor performance. Series A, C, and E had bands in which 

concentrations of blisters occurred and other bands in which there were only a few or no blisters. 

This usually indicates that there is some variance in the coating application (thickness). Series 

B and D were each uniformly covered with blisters, indicating uniformly poor coating 

application or uniformly poor paint. Blistered areas for these two series is roughly the same, 

meaning that the performance is more similar than the ratings would lead one to believe. The 

topcoat specification allows there to be up to five blisters on a 4 in x 12 in after 336 hr of 

8 
, 

exposure to salt fog. When this requirement was written into the specification, preliminary 

testing indicated that blisters did not appear in greater numbers between 336 and 1,000 hr, just 

greater size. If ASTM D714 [ 121 is used to evaluate a panel, it has already failed the preceding 

requirement. As a basis for comparison, 260 panels were run for 2,000 hr of salt fog. One set of 

five panels was phosphated with ML-P-53022 [2] and ML-C-46168 [3] topcoat. Three of the 

five panels went through over 2,000 hr of salt fog with no blisters on any of the panels. The 

remaining two panels also did not have any blistering away from the scribe. Creep went from 

less than 1 miI after 336 hr, to about 3 mil after 1,000 hr, to 5 mil after 2,000 hr. This shows 

that, in spite of having twice the exposure time, the panels from the baseline study performed as 

well as or better than any of those provided for use in the UNICARB study. TACOM asked 

ARL to reexamine the blistered panels. Two panels were chosen at random and were immersed 

in deionized water for 24 hr to reactivate the blisters. Parallel cuts through the coating were 

made in two areas on each of the panels. Tape was applied and removed both with and across 

the cuts. Delamination occurred only on one small area of one of the cuts. A five-in-one tool 

was employed to scrape the coating from each of the panels. Based upon the preceding, the 

delamination is believed to occur at the metal/coating interface. The intercoat adhesion is very 

good, based upon the difficulties encountered while scraping. The blistering and creep 

evaluations are illustrated in Figures 1 and 2, respectively. 

Twenty panels, four replicates for each of the five coating processes, were provided for 

GM 9540P [7] testing. The lower half of each panel was scribed with an X, while the upper half 

was untouched. After the backs and edges were coated with beeswax, panels were exposed to 

100 cycles of GM 954OP [7]. During the course of the test, it was observed that the beeswax had 

melted and may have flowed on to the test panel surfaces, thus invalidating the test results. 

When this test is performed in future programs, beeswax will not be used. Evaluations were 

performed using ASTM D1654 [ 1 l] procedure A for creep from scribe (direct measurements 

were done in millimeters, not the l-10 scale provided) and any corrosion anomalies were noted. 

The unscribed regions performed well in this test without the blisters that characterized the salt 

fog test. This may be because the GM 9540P [7] is a cyclic test that provides the coating an 

opportunity to dry. There were spots on each series of panels, except series E, where rust 

9 
1000 Hours Sdl Fog. Blistering 

10 

9 

a 

7 

6 

5 

4 

3 

2 

1 

0 

Figure 1. Salt Fog Blistering Results. 

1000 Hour Sdt Fog. Scribed 

^ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..-.... . . . . ..-.. . . ._.... ._. . . . . . 

Pa-d IDS 8A26 8A23 mB19 mB21 W27 n C27 q !Dl9 B1D21 n E 19 =E21 

Figure 2. Salt Fog Creep Results. 

10 
bled through the coating. The most spots were seen on series B, followed by series C, A, and D. 

The problem is not particularly severe in that there were only four such spots on the most 

affected panel. However, this is probably indicative of a porous film that has borderline 

thickness thus allowing corrosive solution to the substrate in a short period of time. These 

features, once present, did not grow in size. The performance in the scribed regions exhibited 

distinct trends. At the halfway point of the test, series C had the greatest creep from scribe, with 

an average value of 3.35 mil. Series A and B followed with values of 2.5 mil, and series D and E 

each had averaged values of under 2 mil. The trend continued at 75 cycles, with series C turning 

in the worst performance, followed by series A and B. Series D and E continued to do best. At 

the conclusion of the test, series C had an averaged creep from scribe of 7.1 mil, followed by 

series A at 6.1 mil. Series B, D, and E performed comparably, with averaged creep of under 

5 mil. The panels in this study had less creep from scribe than comparable panels in the water 

reducible polyurethane matrix. Averaged creep was greater than 10 mm. However, these panels 

did not have any of the rust spots on their relatively small, unscribed areas. This performance is 

consistent with an even nonporous primer/topcoat layer, where all damage occurring at a 

manufactured coating defect at the metal-pretreatment interface. The choice of beeswax as a 

back and edge protector for GM 9540 will be avoided in the future, since the temperature 

reached in the high temperature dry off cycle causes the wax to soften or melt. The lower 

melting fractions may have helped protect the test surfaces of the panels by filling in porosity or 

by flowing into the scribe. Averaged performance and creep evaluations are illustrated in 

Figures 3, 4, and 5, respectively. 

As noted in section 1, all of the panels prepared by supercritical CO2 reduction had poor film 

properties, indicated by excessive voids and pinholes. Appearance problems included 

nonuniform color and gloss, and what appeared to be areas showing a “dry spray” appearance. 

In addition, closer inspection of these panels indicated that film porosity could be a problem. 

Examination under minimal magnification revealed apparent holes in these films that were not 

visible in films that had been applied conventionally, either with or without solvent reduction. 

These defects alone were sufficient to fail the panels on spraying properties. However, in order 

11 
Figure 3. GM 954OP [7] Performance Results. 

Figure 4. GM 954OP [7] Creep Evaluation Results. 

12 
A Panels 

B Panels 

C Panels 

Figure 5. Black and White Images. 

13 
D Panels 

E Panels 

Figure 5. Black and White Images (continued). 

to provide a less subjective means to compare all of the dried paint films, color photographs were 

electronically manipulated into black and white renderings in which the paint film was black and 

the holes were white. The following procedure was used to develop these’images. 

(1) All shots were done at 320x magnification, using a Wild Stereo Microscope, and lighted 

using an g-in ring light. 

(2) The color camera was in Y/S-video mode. 

14 
. 

(3) The micrographs were histographicahy adjusted to include the full tails of each 

histograph. 

(4) The micrograph was duplicated, and then adjusted to the peak of the histograph, 

converted to black and white and readjusted to that histographic peak. 

(5) The image was then inverted, followed by threshholding the image at 200 (out of a 

256level grey scale), where 0 = black and 255 = white. 

(6) All image manipulations were performed using Photoshop 5.02. 

Figure 5 illustrates the differences between the five panel sets. 

4. Discubsion 

TACOM and APL’s mutually developed test matrix helps bring to light the poor Elm 

application ability of supercritical CQ with pigmented coatings and the subsequent detrimental 

effects the porous film may impart upon the coating system in a corrosive environment. While 

many critical tests did pass, it is essential that all requirements be met to be an approved coating. 

5. Conclusion 

Detailed conversations between TACOM and ARL team members have resulted in 

requesting Union Carbide and Hen&en to rework both the formulation and application 

procedures to produce a void-free CARC film and to implement and provide an initial transfer 

efficiency baseline with the reformulated coating. This two-step approach would assist all 

interested parties as to the practicality and economical feasibility of implementing the 

supercritical (DJ process. Until this is accomplished and all performance requirements are met, 

the application CARC using the UNICARB (supercritical (DJ reduction) will continue to remain 

an unacceptable process and unapproved coating for the Army. 

15 
hTENTIONALLY LEFT BLANK. 

16 
6. References 

, 

1. 

I 2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

Defense Standardization Program Office. Standardization Directory. SD-6, August 1999. 

U.S. Department of the Army. “Primer, Epoxy Coating, Corrosion Inhibiting, Lead and 

Chromatic Free.“- MIL-P-53022, U.S. Army Research Laboratory, Aberdeen Proving 

Ground, MD, 1 June 1988.. 

U.S. Department of the Army. “Coating, Aliphatic Polyurethane, Chemical Agent 

Resistant.” M&C-46168, U.S. Army Research Laboratory, Aberdeen Proving Ground, 

MD, 19 May 1993. 

U.S. Department of the Army. “Coating, Aliphatic Polyurethane, Single Component, 

Chemical Agent Resistant.” MIL-C-53039, U.S. Army Research Laboratory, Aberdeen 

Proving Ground, MD, 19 May 1993. 

U.S. Department of the Army. Military specification draft. MIL-P-64159, U.S. Army 

Research Laboratory, Aberdeen Proving Ground, MD, in progress. 

American Society for Testing and Materials. “Salt Spray (Fog) Testing.” ASTM B117, 

1990. 

General Motors Corp. “Accelerated Corrosion Testing.” GM 954OP, December 1997. 

U.S. Department of the Navy. “Coating Epoxy, High-Solids.” MIL-PRF-22750, 31 May 

1994. 

American Society for Testing and Materials. “Materials, Nonmetallic, Operating 

Light-Exposure Apparatus (Xenon-Arc Type) With and Without Water for Exposure of.” 

ASTM G26,15 September 1993. 

American Society for Testing and Materials. “Materials, Nonmetallic, Operating Light- and 

Water-Exposure Apparatus (Fluorescent W-Condensation Type) for Exposure of.” ASTM 

G53,1993. 

11. American Society for Testing and Materials. “Specimens, Painted or Coated, Subjected to 

Corrosive Environments, Evaluation of.” ASTM D1654, 15 October 1992. 

12. American Society for Testing and Materials. “Paints, Blistering of, Evaluating of.” 

ASTM D714,28 July 1988. 

17 
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OMB ND. 07W-Ol88 

The Evaluation of Supercritical Ca Application of CARC 

uncan, Donovan Harris, and Christopher Miller 

ATIN AMSRL-WM-h4A 

Aberdeen Proving Ground, MD 21005-5069 Ala-m-2339 

AGENCV REPORT NUMBER 

At the request of the U.S. Army Tank-automotive and Armaments Command (TACOM), the Coating 

I’echnologies Team of the U.S. Army Research Laboratory (ARL), Weapons and Materials Research Directorate 

(WMRD), evaluated a chemical-agent resistant coating.(CARC) reformulated to be compatible with the supercritical 

CO2 application process. Test panels were prepared by the Concurrent Technologies Corporation (CTC) and 

submitted to ARL’s Experimental Products Program (EPP) for approval. Thus far, four different and separate 

formulations have been submitted, and all have Eailed, including the fourth and most recent submission prepared at 

the CTC on 12 November 1999. In each case, excessive voids and pinholes riddled the coating film applied with 

supercritical (2%. To date, the use of supercritical C@ has not been successful in demonstrating its ability to apply 

CAF2Cs fke of voids or pinholes. This report summarizes the test program and the results through 

24 November 1999. 

UNCLA!SIFTED 
hJTENTIONALLY LEFT BLANK. 

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Street or P.O. Box No. 

City, State, Zip Code 

(Remove this sheet, fold as indicated, tape closed, and mail.) 

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DEPARTMENT OF THE ARMY 

I 

I BUSINESS REPLY MAIL 

FIRST CLASS PERMIT NO WDl ,APG,MD I 

NECESSARY 

UNITED STATES 

POSTAGE WILL BE PAID BY ADDRESSEE 

DIRECTOR 

US ARMY RESEARCH LABORATORY 

ATTN AMSRL WM MB 

ABERDEEN PROVING GROUND MD 21OD5-5069