Mechanisms of Military Coatings Degradation: Accelerated 

and Outdoor Exposure Evaluations 

by John A. Escarsega, William S. Lum, and Philip H. Patterson 

ARL-TR-3085 September 2003 

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Army Research Laboratory 

Aberdeen Proving Ground, MD 21005-5069 

ARL-TR-3085 September 2003 

Mechanisms of Military Coatings Degradation: Accelerated 

and Outdoor Exposure Evaluations 

John A. Escarsega, William S. Lum, and Philip H. Patterson 

Weapons and Materials Research Directorate, ARL 

Approved for public release; distribution is unlimited. 
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Mechanisms of Military Coatings Degradation: Accelerated and Outdoor Exposure 

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John A. Escarsega, William S. Lum, and Philip H. Patterson 

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14. ABSTRACT 

The Weapons and Materials Directorate of the U.S. Army Research Laboratory (ARL) has completed a 4-year research 

investigation on identifying and quantifying key degradation mechanisms of legacy and newly developed coatings systems 

used by the U.S. Army, Marine Corps, and Air Force. This study has incorporated numerous analytical tools and methods in an 

effort to better understand the fundamental principles of environmental degradation that lead to coating failures. These 

environmentally related failures are broadly characterized in two different ways: one as minor, such as appearance changes 

(color loss/fade), and the other as catastrophic, such as film protection changes (substrate corrosion). This report will 

summarize the coatings’ appearance performances when exposed to enhanced ultraviolet radiation and to outdoor static 

weathering. Specifically discussed are the results obtained on the coatings’ change in color and specular gloss. These 

evaluations will serve as a performance baseline providing the knowledge required to formulate more durable military coatings. 

Additionally, when correlated with results obtained from other techniques, a failure analysis model can be established 

predicting a coating’s actual field service life. 

15. SUBJECT TERMS

coatings, weathering, color degradation, gloss 

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John A. Escarsega 

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iii

Contents 

List of Figures iv

List of Tables iv

Acknowledgments v

1. Introduction 1

2. Experimental 2

3. Conditions and Evaluations 3

4. Results and Discussions: Appearance Characterization 4

5. Conclusions and Observations 9

6. References 14

Distribution List 16 
iv

List of Figures 

Figure 1. A typical camouflage coating system..............................................................................1 

Figure 2. QUV exposure data: color change of coating systems...................................................7 

Figure 3. Florida exposure data: color change of coating systems................................................8 

Figure 4. Arizona exposure data: color change of coating systems...............................................8 

Figure 5. Gloss values after 27 weeks of QUV exposure.............................................................11 

Figure 6. Gloss values after 97 weeks of Arizona exposure.........................................................11 

Figure 7. Gloss values after 97 weeks of Florida exposure. .........................................................12 

Figure 8. Photographs displaying coating systems after 48 weeks of UV exposure. ...................12 

List of Tables 

Table 1. QUV exposure data: NBS color change from initial color..............................................5 

Table 2. Florida exposure data: color change (Delta E) from initial color....................................6 

Table 3. Arizona exposure data: color change (Delta E) from initial color...................................6 

Table 4. Summary QUV exposure data (averaged): color change from initial color.....................6 

Table 5. Summary of Florida exposure data (averaged): color change from initial color.............7 

Table 6. Summary of Arizona exposure data (averaged): color change from initial color. ..........7 

Table 7. Summary of gloss values for QUV after 27 weeks, radiant energy 

UV: 671.13 MJ/m2

..................................................................................................................10 

Table 8. Summary of gloss values for Arizona after 97 weeks, radiant energy 

UV: 603.52 MJ/m2..................................................................................................................10 

Table 9. Summary of gloss values for Florida after 97 weeks, radiant energy 

UV: 501.37 MJ/m2

..................................................................................................................10 
v

Acknowledgments 

This coating research was supported in part by the U.S. Department of Defense through the 

Strategic Environmental Research and Development Program under the task area of pollution 

prevention (PP-1133). The authors gratefully acknowledge the principal investigator, Ms. 

Wendy Kosik of the U.S. Army Research Laboratory, for her efforts in coordinating and 

managing the many facets of the program. 
vi

INTENTIONALLY LEFT BLANK. 
1

1. Introduction 

The U.S. Army, Marine Corps, and Air Force use polyurethane coatings as camouflage 

“topcoats” and epoxy coatings as “primers” on all tactical vehicles and aircraft. Pretreatments 

for the substrates vary depending upon the composition of the vehicle or aircraft and whether it is 

a refurbished item or a piece of original equipment from the manufacturer (OEM). In either 

case, it is typically a chromated wash primer for refurbished equipment and an alodine-based 

conversion coating for aluminum (Al) or zinc phosphate based material for ferrous substrates for 

OEMs. This “coating system” not only serves to provide camouflage for vehicles and aircraft 

but also provides protection against chemical warfare agents for the U.S. Army and Marine 

Corps with their chemical agent resistant coatings (CARCs). A visual schematic of the system is 

shown in figure 1. The coatings must retain their physical properties over a broad temperature 

range in widely varying climatic environments. The coating system is the first line of defense in 

preventing corrosion, thereby extending the life cycle of a military vehicle or aircraft. In an 

effort to specifically minimize overall vehicle corrosion and reduce costly refurbishment and 

maintenance expenditures, an ongoing tri-service research effort has been established to examine 

the mechanism and relationships involving the coatings’ degradation. Four polyurethane topcoat 

and epoxy primer coating systems representing the U.S. Army, Marine Corps, and Air Force 

were selected. Standard specification, as well as newly developed, “greener” materials, were 

evaluated. This report will present data on gloss, color, and general appearance changes 

occurring in samples exposed in Arizona and Florida, as well as in an accelerated ultraviolet light 

(QUV)* chamber. The weathering effects on topcoat degradation and “coating system” 

interaction will be discussed. 

Topcoat (50-75 microns)

-Aliphatic polyurethane

-Highly filled - flat paint

-CARC,signature, and other

 requirements

Primer (25-35 microns)

-BPA epoxy based

-Corrosion inhibited 

-Highly adherent

Substrate

Pretreatment

-Substrate dependent

-Provides bondable surface 

 and corrosion protection

Figure 1. A typical camouflage coating system.

 *

 QUV is a registered trademark of the Q-Panel Company. 
2

2. Experimental 

The coatings were sprayed onto two different metal substrates, cold-rolled steel (SAE 1008) 

panels pretreated with zinc phosphate (Bondrite 37*

) and a chromate sealer (Parcoolene 60 †) 

conforming to TT-C-490 (1) and 2024 T3 Al alloy panels pretreated with a chemical conversion 

(Iridite 14-2‡) conforming to MIL-C-5541 (2). Free films were also prepared with only the 

topcoats sprayed onto a low surface tension Tedlar polyvinyl fluoride (DuPont Inc., Buffalo, 

NY) release film. Additionally, a primer and topcoat system were also prepared onto a stainless 

steel mesh substrate for additional thermal analysis conducted by the Marine Corps. Only color 

data from the QUV exposures were obtained for these samples, due to their irregular surface. 

The panels and free films were sprayed to a dry film thickness of 50–65 μm for the topcoats and 

25–37 μm for the epoxy primers (applied to the metal panels only). Film thickness for the 

stainless steel mesh required additional primer and topcoat to adequately eliminate any surface 

defects and resulted in a total film thickness of 155 μm. The topcoat formulations reported in 

this paper were pigmented to conform with U.S. Army color number 34094 (Green 383) as 

stated in MIL-C-46168 (3), the military’s specification for two-component, chemical agent 

resistant, polyurethane coatings, and Air Force color number 36375 (Medium Gray) as 

referenced in MIL-PRF-85285 (4), the military’s specification for high-solids polyurethane 

coatings. 

The water-dispersible formulations are identified as Systems “B” and “D.” The solvent-based 

formulations are designated as “A” and “C.” The Army’s water-dispersible topcoat (Part of 

System “B”) is formulated with water-dispersible hydroxy-functional polyurethane and a 

water-dispersible polyisocyanate. The coating’s pigment package includes prime pigments used 

to make the Army’s camouflage color number 34094 (Green 383), as well as polymeric-type 

extenders for flattening purposes. While the water-dispersible topcoat of System “D” uses no 

polymeric flattening agents and is pigmented to Air Force color number 36375 (Medium Gray). 

The solvent based topcoats also use nonpolymeric flattening agents and incorporate their 

respective prime pigments for the Army color number 34094 (Green 383), System “A,” and the 

Air Force color number 36375 (Medium Gray), System “C.” 

Summary of Coating Systems: 

• A = MIL-C-46168, Army Control System

Top Coat: MIL-C-46168 TYPE IV solvent-based polyurethane (siliceous extender) 

 *

 Bondrite 37 is a registered trademark of ACT Laboratories, Inc. 

†

 Parcoolene 60 is a registered trademark of ACT Laboratories, Inc. 

‡

 Iridite 14-2 is registered trademark of the Q-Panel Company. 
3

Primer: MIL-P-53022 (5) solvent-based epoxy 

Surface Treatment: TT-C-490 zinc phosphate on a steel substrate 

• B = MIL-DTL-64159-TYPE II, Zero Hazardous Air Pollutants 

With Polymeric Flattening Agents (6, 7) 

Top Coat: Water Dispersible CARC polyurethane (polymeric bead extenders) 

Primer: MIL-P-53030 (8) water-based epoxy 

Surface Treatment: TT-C-490 zinc phosphate on a steel substrate 

• C = MIL-PRF-85285, Navy Control System 

Top Coat: MIL-PRF-85285 solvent-based polyurethane 

Primer: MIL-PRF-23377 (9) solvent-based epoxy 

Surface Treatment: MIL-C-5541 chemical conversion on Al substrate 

• D = MIL-PRF-85285 TYPE III (Zero VOC Top Coat) 

Top Coat: Zero VOC top coat water-based polyurethane 

Primer: MIL-PRF-85582 (10) water-based epoxy 

Surface Treatment: MIL-C-5541 chemical conversion on an Al substrate 

3. Conditions and Evaluations 

Three types of exposures were conducted, two at separate outdoor weathering locations (Florida 

and Arizona) and one in an accelerated UV weathering (QUV) chamber. The test procedures 

established for the Arizona and South Florida exposures conform to American Society for 

Testing and Materials (ASTM) G-7 (11) and ASTM G-147 (12). The exposure testing was 

performed in Miami, FL (26° N) and New River, Arizona (34° N) in accordance with the ASTM 

Governing Standards at a tilt angle of 5° from the horizontal facing south. The exposure 

intervals ranged from 7 to 97 weeks. The accelerated UV testing was conducted using a 

weathering chamber operated under the requirements established by ASTM G-53 (13). Cycling 

involved total UV light exposure with no condensation or water spray. A series of UVA 340 

lamps were used as the light source set to emit a spectral irradiance of 0.77 W/m2

. An automatic 

sensor controller kept this irradiance level measured at 340 nm, stable throughout the testing and 

was calibrated after every 400 hr of lamp operation. An exposure temperature of 60 °C was 

maintained inside the weathering chambers. The study was conducted following an elapsed time 

schedule, with the samples exposed to continuous UV over the intervals of 3–48 weeks. With 

each timed interval, the solar UV energy dosage was recorded as well. 

After each exposure interval, the samples were rinsed with deionized water and allowed to dry 

before color and gloss measurements were made. During the performance testing, all specimens 

were carefully handled to avoid marring, and the operators wore lint-free gloves in order to keep 

coating surfaces clean. 
4

For the outdoor exposures, color measurements were performed on a Hunterlab Ultrascan 

Colorimeter with a 6-in integrating sphere. Color measurements for the QUV exposures were 

made using a Data Color Chroma Sensor Spectrophotometer equipped with an 8-in integrating 

sphere. In both cases, the spheres were set up to include the specular component of the sample’s 

reflectance. All of the color readings were made in accordance to ASTM D-2244 (14) using a 

2° observer under illuminant C. 

Gloss measurements were made in accordance with ASTM D-523 (15) using a BYK Gardner 

GB4606 Haze-Gloss Reflectometer. The measurements were taken at 60 and 85°. The 

instrument was calibrated using the manufacturer’s reflectometer standard gloss tile. A 

BYK-Gardner Micro-Tri-Gloss portable glossmeter was used for the outdoor exposures. 

4. Results and Discussions: Appearance Characterization 

The results from all of color measurements made on the samples’ QUV, Florida, and Arizona 

exposures are provided in tables 1–3, respectively. Tables 4–6 are averaged measurements 

provided to simplify the data. Additionally, the averaged data are shown in figures 2–4. It 

should be noted that listed in the last eight columns of table 1 are color data obtained from 

specifically prepared samples. These coatings were prepared as either free films (T designation) 

or having a screen mesh (B designation) as its substrate. 

From reviewing table 4, it is apparent that of the four coating systems evaluated, System “A,” 

using the MIL-C-46168 solvent-based polyurethane topcoat, shows the most pronounced signs of 

appearance degradation due to accelerated UV exposure. Severe color fade/degradation (3.23 

color-difference units) occurs after just 6 weeks/149.1 MJ/m2

 (UV dosage) of exposure. The 

change is primarily due to an increase in the brightness of the coating’s color. It is interesting to 

note that this degradation trend continues throughout the remaining exposure intervals. 

Conversely, the UV color stability is best for the topcoats used in the water-based systems 

(“B” and “D”). This weathering characteristic is almost certainly related to the coatings’ 

extender pigment content for the topcoats (16). A comparison of the pigment to binder (resin) 

ratio is greatest for the System “A” topcoat (2:1 pigment/binder ratio), and the least is System 

“B” with “C” and “D” falling in between. 

The test results from Florida and Arizona outdoor weathering provide insight to the effects of 

humidity and moisture on the exposed coatings. Because the Arizona environment has very little 

humidity or moisture (i.e., rain), degradation effects are primarily the result of UV radiation. 

However, the Florida environment has a significant amount of humidity and moisture in 

conjunction with UV radiation that often accelerates the degradation of organic coatings. 

As table 5 shows, the System “B” topcoat, MIL-PRF-64159 (17), water dispersible polyurethane,

exhibited the smallest change in color of all the coatings exposed in South Florida. This 
5

Table 1. QUV exposure data: NBS color change from initial color. 

 Sample Code 

Exposure Time, Radiant UV Energy AA BA CA DA AN BN CN DN AM BM CM DM AMT AMB BMT BMB CMT 

3 weeks, 74.57 

MJ/m2

0.45 0.44 0.33 0.46 0.57 0.67 0.27 0.45 0.38 0.55 0.32 0.39 0.34 0.70 0.62 0.72 0.31 

6 weeks, 149.14 

MJ/m2

3.50 0.54 0.26 0.56 3.40 0.53 0.28 0.54 2.8 0.63 0.4 0.47 3.30 2.50 0.74 0.76 0.37 

12 weeks, 298.28 

MJ/m2

5.30 0.67 0.28 0.69 6.30 0.72 0.47 0.71 5.9 0.87 1.40 0.65 7.90 7.70 0.8 0.98 1.70 

18 weeks, 447.42 

MJ/m2

8.60 0.82 0.26 0.78 7.75 0.98 1.38 0.77 7.85 0.89 2.09 0.75 8.59 8.49 0.86 0.91 8.20 

27 weeks, 671.13 

MJ/m2

10.37 0.82 No 

data 

No data 

10.68 0.93 3.36 1.01 11.35 0.95 No 

data 

No data 

— — — — — 

36 weeks, 894.84 

MJ/m2

12.10 0.93 No 

data 

No data 

12.59 1.16 4.96 1.01 12.00 1.03 No 

data 

No data 

— — — — — 

48 weeks, 1193.12 

MJ/m2

12.86 1.04 5.47 0.74 13.30 1.34 5.99 1.15 13.35 1.30 6.13 0.68 — — — — — 

Notes: sample code key: 

First letter: A = Coating System “A,” B = Coating System “B,” C = Coating System “C,” and D = Coating System “D.” Second letter: A = Test Sample 1, N = Test Sample 2, and M = Test Sample 3. 

Third letter: T = samples tested as a free film, and B = sample films applied and tested on grid substrate. 
6

Table 2. Florida exposure data: color change (Delta E) from initial color. 

 Sample Code 

Exposure Time, 

Radiant UV Energy AA BA CA DA AN BN CN DN AM BM CM DM 

7 weeks, 75.03 

MJ/m2 0.11 0.90 0.39 0.96 0.13 0.95 0.35 0.99 0.20 0.78 0.39 0.86 

13 weeks, 91.15 

MJ/m2 0.54 1.12 0.34 1.31 0.42 1.1 0.44 1.32 0.42 1.15 0.18 1.28 

25 weeks, 151.41 

MJ/m2 2.60 1.12 0.59 1.34 2.31 1.22 0.42 1.43 2.73 1.26 0.42 1.34 

49 weeks, 270.65 

MJ/m2 4.90 1.32 0.79 3.33 4.67 1.32 0.87 2.73 5.14 1.22 0.92 3.91 

97 weeks, 501.37 

MJ/m2 7.70 1.53 2.74 2.70 7.31 1.57 2.61 3.25 7.26 1.59 2.52 2.83 

Table 3. Arizona exposure data: color change (Delta E) from initial color. 

 Sample Code 

Exposure Time, 

Radiant UV Energy AA BA CA DA AN BN CN DN AM BM CM DM 

7 weeks, 65.29 MJ/m2 0.33 0.59 0.14 0.23 0.51 0.76 0.165 0.21 0.65 0.71 0.16 0.21

13 weeks, 120.08 

MJ/m2 0.59 0.81 0.27 0.61 0.54 0.91 0.18 0.64 0.55 0.91 0.28 0.63

25 weeks, 203.40 

MJ/m2 3.02 1.23 0.46 0.95 3.46 1.24 0.52 0.95 3.29 1.30 0.48 0.87

49 weeks, 305.37 

MJ/m2 4.89 1.28 1.75 0.40 4.60 1.27 1.28 0.51 4.81 1.33 1.65 0.48

97 weeks, 603.52 

MJ/m2 9.03 1.30 4.12 1.98 9.39 1.30 3.80 1.45 9.31 1.32 3.59 1.75

Table 4. Summary QUV exposure data (averaged): color change from 

initial color. 

 Coating System 

Exposure Time, Radiant 

UV Energy A B C D 

3 weeks, 74.57 MJ/m2 0.47 0.55 0.31 0.43 

6 weeks, 149.14 MJ/m2 3.23 0.57 0.31 0.52 

12 weeks, 298.28 MJ/m2 5.83 0.75 0.72 0.68 

18 weeks, 447.42 MJ/m2 8.07 0.90 1.24 0.77 

27 weeks, 671.13 MJ/m2 10.80 0.90 3.36 1.01 

36 weeks, 894.84 MJ/m2 12.23 1.04 4.96 1.01 

48 weks, 1193.12 MJ/m2 13.17 1.23 5.86 0.86 
7

Table 5. Summary of Florida exposure data (averaged): color 

change from initial color. 

 Coating System 

Exposure Time, Radiant 

UV Energy A B C D 

7 weeks, 75.03 MJ/m2 0.15 0.88 0.38 0.94 

13 weeks, 91.15 MJ/m2 0.46 1.12 0.32 1.30 

25 weeks, 151.41 MJ/m2 2.55 1.2 0.48 1.37 

49 weeks, 270.65 MJ/m2 4.92 1.29 0.86 3.32 

97 weeks, 501.37 MJ/m2 7.42 1.56 2.62 2.93 

Table 6. Summary of Arizona exposure data (averaged): color 

change from initial color. 

Coating System 

Exposure Time, Radiant UV 

Energy A B C D 

7 weeks, 65.29 MJ/m2 0.50 0.69 0.16 0.22 

13 weeks, 120.08 MJ/m2 0.56 0.88 0.24 0.63 

25 weeks, 203.4 MJ/m2 3.26 1.26 0.49 0.92 

49 weeks, 305.37 MJ/m2 4.77 1.29 1.56 0.46 

97 weeks, 603.52 MJ/m2 9.24 1.31 3.84 1.73 

0.5

3.2

5.8

8.1

10.8

12.2

13.2

0.6

0.6

0.8

0.9

0.9

1.0

1.2

0.30.3

0.7

1.2

3.4

5.0

5.9

0.4

0.5

0.7

0.8

1.01.0

0.9

0

2

4

6

8

10

12

14

3 Weeks, 74.57

MJ/m2

6 Weeks, 149.14

MJ/m2

12 Weeks, 298.28

MJ/m2

18 Weeks, 447.42

MJ/m2

27 Weeks, 671.13

MJ/m2

36 Weeks, 894.84

MJ/m2

48 Weeks,

1193.12 MJ/m2

Exposure Time, Radiant UV Energy

Note: 270 MJ/m2 is equal to about 1 year of exposure

ColorUnits

MIL-C-46168, ARMY CONTROL SYSTEM

MIL-DTL-64159 TYPE II, ZERO HAPs 

MIL-PRF-85285, NAVY CONTROL SYSTEM

MIL-PRF-85285 TYPE III (ZERO VOC TOP

COAT) 

Figure 2. QUV exposure data: color change of coating systems. 
8

0.2

0.5

2.6

4.9

7.4

0.9

1.1

1.2

1.3

1.6

0.4

0.3

0.5

0.9

2.6

0.9

1.3

1.4

3.3

2.9

0

1

2

3

4

5

6

7

8

7 Weeks, 75.03 MJ/m2 13 Weeks, 91.15 MJ/m2 25 Weeks, 151.41 MJ/m2 49 Weeks, 270.65 MJ/m2 97 Weeks, 501.37 MJ/m2

Exposure Time, Radiant UV Energy

Note: 270 MJ/m2 is equal to about 1 year of exposure

Color Units

MIL-C-46168, ARMY CONTROL SYSTEM

MIL-DTL-64159 TYPE II, ZERO HAPs

MIL-PRF-85285, NAVY CONTROL SYSTEM

MIL-PRF-85285 TYPE III (ZERO VOC TOP COAT) 

Figure 3. Florida exposure data: color change of coating systems. 

0.5

0.6

3.3

4.8

9.2

0.7

0.9

1.3

1.3

1.3

0.2

0.2

0.5

1.6

3.8

0.2

0.6

0.9

0.5

1.7

0

1

2

3

4

5

6

7

8

9

10

7 Weeks, 65.29 MJ/m2 13 Weeks, 120.08

MJ/m2

25 Weeks, 203.4

MJ/m2

49 Weeks, 305.37

MJ/m2

97 Weeks, 603.52

MJ/m2

Exposure Time, Radiant UV Energy

Note: 270 MJ/m2 is equal to about 1 year of exposure

Color Units

MIL-C-46168, ARMY CONTROL SYSTEM

MIL-DTL-64159 TYPE II, ZERO HAPs 

MIL-PRF-85285, NAVY CONTROL

SYSTEM

MIL-PRF-85285 TYPE III (ZERO VOC TOP

COAT) 

Figure 4. Arizona exposure data: color change of coating systems. 
9

subtropical environment was most detrimental (loss of color retention) to the System “A” coating, 

which displayed a color difference value of 7.42 units at the final weathering interval. Also, at this 

interval, the topcoats from both System “C” and “D” showed significant color degradation (~3 

units). The color retention for the System “D” topcoat was actually compromised at the previous 

exposure interval, 49 weeks/270.6 MJ/m2 (UV dosage), whereas with System “C,” the color 

remained stable. It should be noted, this behavior for coating “D” did not manifest itself under the 

Arizona or the QUV exposures. This is an example of how humidity and moisture combined with 

UV radiation synergistically increase the degradation of a specific coating. 

As summarized in table 6, the color retention is good for all of the coating systems through the first 

13 weeks of weathering in Arizona. It is not until 25 weeks /203.4 MJ/m2

 (UV dosage) of 

exposure that the degradation trends begin to appear. As with the QUV exposures, the topcoat of 

System “A” is the first to show a visually significant color change (3.26 units). System “C,” using 

the MIL-PRF-85285, solvent-based polyurethane topcoat, was the second most susceptible coating 

to color degradation, with a major color change (3.84 units) occurring after 97 weeks/603.5 MJ/m2 

(UV dosage) of exposure. Overall, the degradation trend and performance ranking for these 

coatings are in line with the results obtained from the QUV exposures. 

The coatings’ gloss values for both 60 and 85° are summarized in tables 7–9 and charted in figures 

5–7. The data were taken from the final evaluation interval (97 weeks) for the outdoor exposures 

and 27 weeks for the QUV exposure. This QUV interval was chosen to match, as closely as 

possible, the total UV energy dosage to that of the outdoor exposures. The gloss changes for the 

low matte samples, Systems “A” and “B” is minimal. Even the change in the 85° gloss reading 

(1.2 unit increase) for the “System “B” topcoat, under the Florida exposure, is an acceptable 

difference. For the higher gloss coatings, Systems “C” and “D,” all of the weathering results show 

a similar gloss change trend; that is, a decrease in 60° gloss and an increase in the 85° gloss. The 

one exception to this trend was the loss of 85° gloss for System “D” in Florida, although in its 

previous exposure interval (49 weeks), the 85° reading did indeed rise. No explanation for this 

data reversal is readily apparent. These gloss degradation trends are best explained by the way in 

which formulators generally use larger particle-sized pigments to lower the 85° gloss reading. As 

the coating film weathers and the binder degrades, these pigments are lost and a new surface 

topography develops that is generally smoother, thus giving rise to the 85° reading and a lowering 

of the 60° reading. 

5. Conclusions and Observations 

• The protective film properties of all of the “Coating Systems” remained intact. No 

catastrophic failures (i.e., cracking, checking, blistering, and delaminating) occurred under 

any of the exposure conditions. 
10

Table 7. Summary of gloss values for QUV after 27 weeks, radiant 

energy UV: 671.13 MJ/m2

. 

QUV Initial Final Initial Final 

System Gloss 60° Gloss 60° Gloss 85° Gloss 85° 

A 0.6 0.7 2.9 2.5 

B 0.7 0.8 1.6 2.2 

C 2.3 1.6 3.6 3.8 

D 2.1 1.4 4.4 4.3 

Table 8. Summary of gloss values for Arizona after 97 weeks, radiant 

energy UV: 603.52 MJ/m2

. 

Arizona Initial Final Initial Final 

System Gloss 60o Gloss 60o Gloss 85o Gloss 85o

A 0.6 0.6 3.6 3.4 

B 0.6 0.6 2.2 2.5 

C 2.1 1.4 4.1 8.7 

D 2.0 1.3 5.4 6.6 

Table 9. Summary of gloss values for Florida after 97 weeks, radiant 

energy UV: 501.37 MJ/m2

. 

Florida Initial Final Initial Final 

System Gloss 60° Gloss 60° Gloss 85° Gloss 85° 

A 0.6 0.5 3.2 4.4 

B 0.7 0.6 2.2 2.8 

C 2.2 1.6 4.5 6.4 

D 1.9 1.0 5.3 3.7 

• The water dispersible coatings “B” and “D” provided much better resistance to color 

changes than their solvent-based counterparts, “A” and “C,” when weathered under the 

QUV conditions (figure 8). The Arizona results paralleled these findings, an indication 

that the coatings’ degradation pathways (i.e., photolysis) are similar. 

• For the Florida exposures, as with the other two exposure conditions, coating “B” 

outperformed coating “A” for color retention. However, for the Air Force systems, coating 

“D” reversed its excellent color retention behavior, as seen in the Arizona/QUV exposures. 

This system was actually the first of all the coatings to show significant color deterioration. 

This reversal indicates that for this coating, the subtropical environment created or 

enhanced a degradation mechanism that adversely impacted color durability greater than 

that of the arid exposures.
11

0.6

0.7 2.9

2.5

0.7

0.8

1.6

2.2

2.3

1.6

3.6

3.8

2.1

1.4

4.4

4.3

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

G loss 60o G loss 60o G loss 85o G loss 85o

Initial F inal Initial F inal

Gloss Units

M IL-C -46168, AR M Y C O N TR O L SYSTEM

M IL-D T L-64159 T YP E II, ZE R O H A P s 

M IL-PR F-85285, N AVY C O N TR O L SYSTEM

M IL-P R F-85285 T YP E III (ZE R O V O C T O P C O A T ) 

Figure 5. Gloss values after 27 weeks of QUV exposure. 

0.60.6

3.6

3.4

0.6

0.6

2.2

2.5

2.1

1.4

4.1

8.7

2.0

1.3

5.4

6.6

0

1

2

3

4

5

6

7

8

9

1 0

G loss 60o G loss 60o G loss 85o G loss 85 o

Initial F inal Initial F inal

Gloss Units

M IL-C -46168, AR M Y C O N TR O L SYST EM

M IL-D TL-64159 T YPE II, ZER O H APs

M IL-PR F-85285, N AV Y C O N TR O L SYST EM

M IL-PR F-85285 TYPE III (ZE R O VO C TO P C O A T) 

Figure 6. Gloss values after 97 weeks of Arizona exposure. 
12

0.6

0.5

3.2

4.4

0.7

0.6

2.2

2.8

2.2

1.6

4.5

6.4

1.9

1.0

5.3

3.7

0

1

2

3

4

5

6

7

G loss 60o G loss 60o G loss 85o G loss 85o

Initial Final Initial Final

Gloss Units

M IL-C-46168, ARM Y CO NTRO L SYSTEM

M IL-DTL-64159 TYPE II, ZERO HAPs

M IL-PRF-85285, NAVY CO NTRO L SYSTEM

M IL-PRF-85285 TYPE III (ZERO VO C TO P CO AT) 

Figure 7. Gloss values after 97 weeks of Florida exposure. 

Figure 8. Photographs displaying coating systems after 48 weeks of UV exposure. 
13

• The topcoat formulation with the lowest pigment to binder ratio (System “B”) provided the 

best overall appearance stability. The performance of this camouflage coating was not 

enhanced by the addition of UV inhibitors or Hindered Amine Light Stabilizers, but rather 

through the selection of durable and effective flattening agents (extender pigments) that 

kept the gloss down while maintaining the low pigment-to-binder ratio. 

• Overall, the weathering exposures had little significant impact on the gloss behavior of the 

coating systems. The gloss changes that did occur, in most instances, were within the 

tolerances as set forth in the coating’s respective specification. 

• Systems “A” and “B” (383 Green pigmentation) have lower reflectance values than “C” 

and “D” (Air Force Medium Gray color number 36375). It is generally accepted that 

higher reflectance properties result in lower ambient operating temperatures (18). 

Therefore, by formulating a topcoat “B” binder system with medium gray pigmentation 

and polymeric flattening agents, color retention would improve due to higher pigment 

reflectance properties and to superior polymer durability. 

• The changes in surface appearance properties affected by environmental exposures are but 

one way of evaluating a coating’s durability. Changes can occur on the surface that may or 

may not impact the bulk of the material. This research included additional degradational 

analysis that measured some of the coatings’ intrinsic properties. The details of the 

instrumental analysis characterizing the functional changes involving the coatings’ 

chemical and mechanical properties will be discussed in a future technical report. 
14

6. References 

1. TT-C-490, Revision D. Cleaning Methods for Ferrous Surfaces and Pretreatments for 

Organic Coatings 1993. 

2. MIL-C-5541, Revision E. Chemical Conversion Coatings on Aluminum and Aluminum 

Alloys 1990. 

3. MIL-C-46168, Revision D. Coating, Aliphatic Polyurethane, Chemical Agent Resistant

1987. 

4. MIL-PRF-85285, Revision D. Coating: Polyurethane, Aircraft and Support Equipment

2002. 

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

1988. 

6. Crawford, D. Analysis and Performance of Water-Dispersible Camouflage Coatings. 

International Waterborne, High-Solids, and Powder Coatings Symposium, New Orleans, 

LA, 6–8 February, 2002. 

7. Escarsega, J. A.; Crawford, D. M.; Duncan, J. L.; Chesonis, K. G. Water-Reducible PUR 

Coatings for Military Applications. Modern Paint and Coatings 1997. 

8. MIL-P-53030. Primer Coatings, Epoxy, Water Reducible, Lead and Chromate Free 1992. 

9. MIL-PRF-23377. Primer Coatings: Epoxy, High Solids 2002. 

10. MIL-PRF-85582. Primer Coatings: Epoxy, Waterborne 2002. 

11. ASTM G-7. Standard Practice for Atmospheric Environmental Exposure Testing of 

Nonmetallic Materials 1999. 

12. ASTM G-147. Standard Practice for Conditions and Handling of Nonmetallic Materials for 

Natural and Artificial Weathering Tests 1999. 

13. ASTM G-53. Standard Practice for Operating Light and Water Apparatus-Fluorescent 

Ultraviolet (UV)/Condensation Type-for Exposure of Nonmetallic Materials 1991. 

14. ASTM D-2244. Standard Test Method for Calculation of Color Differences From 

Instrumentally Measured Color Coordinates 1995. 

15. ASTM D-523. Standard Test Method for Specular Gloss 1995. 

16. Patton, T. C. Paint Flow and Pigment Dispersions, 2nd ed; John Wiley Interscience: New 

York, 1979. 
15

17. MIL-PRF-64159. Coating, Water Dispersible Aliphatic Polyurethane, Chemical Agent 

Resistant 2002. 

18. Akbari, H.; Davis, S.; Dorsano, S.; Huang, J.; Winnett, S. Cooling Our Communities: A 

Guidebook on Tree Planting and Light-Colored Surfacing; 22P-2001; U.S. Environmental 

Protection Agency: Washington, DC, January 1992. 
NO. OF NO. OF 

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