A study was undertaken to determine the durability of nickel-black chromium plated aluminum in an outdoor rural industrial, and seacoast environment. Test panels were exposed to these environments for 60, 36, and 13 months, respectively. The results of this study showed that no significant optical degradation occurred from exposure to either of these environments, although a considerable amount of corrosion occurred on the panels exposed to the seacoast environment. The rural and industrial atmosphere produced only a slight amount of corrosion on test panels

Lowery, J. R.

English

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MBFC - Form 3190 (Rev jam 1971)
NASA TECHNICAL
MEMORANDUM
NASA TM•82454
(NASA—Ttl-81454) A(
E,'tHc VCHBCMIUtl A (NASA) BI 13Tp OF
	
N82-19357
E.LECZAOPLAT ED BL
tiC A02	 CSCL 
11F/tlF A01	 unclas
G3/26 09180
ENVIRONMENTAL DURABILITY OF ELECTROPLATED
BLACK CHROMIUM
By James R. Lowery
Materials and Processes Laboratory
December 1981
MC^A ^CNASA
B^1Z9Z
George C. Marshall Space  Fli ht Centerg
Marshall Space  Flig ht Center, Alabama
i
a
5
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7=IftYYA!!AA awsAa♦ AWAIAN %oft TITi f MAA n '
1. REPORT NO. Z. GWMNWW ACCESSION N0. s. 49CIPINWOO CATALOG NO.
NASA TM-82454
4. TITLE AND SUSTITLE s. RNPORT OATH
December 1981
Environmental Durability of Electroplated Black Chromium G. PERFORMING ORGANIZATION CODE
7. AUTNORIS
James k. Lowery
N. PERFORMING ORGANIZATION Repair N
s. PERFORMING ORGANIZATION NAME AND ADDRESS 10. WORK UNIT, N0.
George C. Marshall Space Flight Center
Marshall Space Flight Center, Alabama	 35812
11. CONTRACT OR GRANT NO.
is. TYPE OF REPORT	 PERIOD COVERED
12. SPONSORING AGENCY NAME AND ADDRESS
National Aeronautics and Space Administration Technical Memorandum
Washington, D.C.
	 20546 14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Prepared by Materials and Processes Laboratory, Science and Engineering.
IS. ASSTRACT
A study was undertaken to determine the durability of nickel-black chromium plated aluminum
in an outdoor rural, industrial, and seacoast environment.
	 Test panels were exposed to these environ-
ments for 60, 36, and 13 months, respectively.
	 The results of this study showed that no significant
optical degradation occurred from exposure to either of these environments, although a considerable
amount of corrosion occurred on the panels exposed to the seacoast environment.
	 The rural and
industrial atmosphere produced only a slight amount of corrosion on test panels.
17. KEV WORDS	 IS. "	 'TRISUTION STATEMENT
19. SECURITY CLASSIF. (d this nptl 20. SECURITY CLASSIF. (6t tha Mp) 21. N0. OF PAGES 22.	 PRICE
Unclassified Unclassified NTIS
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TABLE OF CONTENTS
Page
	
INTRODUCTION ................................................................	 I
	
EXPERIMENTAL PROCEDURE ....................................................	 I
	
DISCUSSION AND RESULTS .....................................................	 2
	
RuralEnvironment ......................................................... 	 2
	
SeacoastEnvironment ...................................................... 	 2
	
Industrial Environment ...................................................... 	 3
	
CONCLUSIONS........ ......................................................... 	 3
	
REFERENCES ..................................................................	 9
LIST OF ILLUSTRATIONS
Figure	 Title	 Pap
1. "Roll-Bond" panel design ................................................... 	 4
2. Atmospheric exposure test racks, located at MSFC ............................. 	 4
3. Nickel-Black chromium electroplated "Roll-Bond" panels after atmospheric
exposure at MSFC, exposure time 60 months .................................	 5
4. Atmospheric exposure racks located on the beach at KSC ....................... 	 S
5. Nickel-black chromium electroplated "Roll-Bond" panels after atmospheric
exposure at KSC, exposure time 13 months .................................. 	 6
6. Atmospheric exposure site, located at the top of an office building at
ACIPCO in Birmingham, Alabama ........................................... 	 7
7. Nickel-black chromium electroplated "Roll-Bond" panels sfter atmospheric
exposure at AC1PCO in Birmingham, Alabama, exposure time 36 months .......... 	 7
LIST OF TABLES
'fable	 Title	 Page
I.	 Effect of Rural Outdoor Environment on the Solar Energy
Absorption Characteristics of Black Chromium ................................ 	 8
'_.	 Effect of Seacoast Environment on the Solar Energy
Absorption Characteristics of Black Chromium ................................ 	 8
3.	 Ef'f'ect of an Industrial Environment on the Solar Energy
Absorption Characteristics of Black Chromium ................................ 	 8
I
a	 1
P*	 I
iv
TECHNICAL MEMORANDUM
ENVIRONMENTAL DURABILITY OF ELECTROPLATED
BLACK CHROMIUM
INTRODUCTION
One major component of a device for collecting molar energy is the receiving surface or solar
absorption panel. These panels are usually prepared from metals which are specially coated to increase
their solar absorptance without significantly lowering their emissivity. Such optically selective surfaces
are often expressed in terms of a solar absorptance /IR emittance ratio. Generally, the higher the ratio
the greater the efficiency of the surface in terms of collecting solar energy. However, it is considered
more beneficial to have coatings with very high solar absorptances (0.90 or higher) and moderately
high emittances (0.1 to 0.2). To obtain such optical selectivity, extremely thin coatings are required
which limit their ability to protect substrates front 	 environments. Even though collector
coven furnish substantial protection from such environments, this presents a problem in the coating
of solar panels because the receiving surface must remain essentially free from corrosion for the
absorption efficiency of the solar panel to remain high. Therefore, the absorber coating itself should
have good resistance to moisture and other corrosive environments, as well as the ability to protect
the substrate material.
Among several black absorber coatings that have shown good absorption characteristics (absorp-
tances higher than 0.9 and emittances around 0.0 is electroplated black chromium. .Results of labora-
tory accelerated corrosion tests j i 1 have also shown that its optical properties are not significantly,
affected by corrosive environments; and when plated over all 	 coating, such as nickel, it
protects substrate materials from corrosion. However, there appears to be no available data on the
results of long-term natural environmental tests. Because of the difficulty of correlating laboratory
test data with outdoor environments and because of the long life expectancy of solar collectors, a
program was conducted to determine the long-term durability of electroplated black chromium in
several different outdoor environments. This report presents the results of the study.
EXPERIMENTAL PROCEDURE
The test panels used in this program were 0.61 m by 0.91 in (2 ft by 3 ft) in size and in the
form of flat sheets containing integral flow passages fabricated by the silk screen/hot roll process.
The panels, constructed of 1100 aluminum, were manufactured by the Olin Brass Company and
marketed under the trade name "Roll-Bond." The panel design was identical to Absorber panel€ in
solar collectors used in a solar residential heating and cooling system develol nient program, conducted
by NASA at the Marshall Space Flight Center (MSFC) (21. A sketch of the panel design is shown
in Figure 1. The aluminum panels were first plated with bright nickel to a thickness of approximately
0.0127 mm (0.0005 in.) to furnish better corrosion protection. The black chromium was then plated
over the nickel (ail the plating was done in a commercial facility) to a thickness sufficient to produce
a high solar absorptance yet thin enough to maintain the low emittance (high infrared reflectance) of
the bright nickel.
W,
The durability of the nickel-black chromium electroplate was established for three different
natural corrosive environments by exposing the panels outside at MSFC, on the coast at Kennedy
Space Center (KSC), and at the American Cast Iron and Pipe Company (ACIPCO) in Birmingham,
Alabama, these exposure sites representing a rural, a seacoast, and an industrial environment. The
panels were exposed bare to represent a worst-case condition. The optical properties of test panels
were determined by taking the average of at least three measurements made at different locations on
each panel (generally in the middle and at each end). These determinations were made before,
periodically during the exposure periods, and at the end of the test. Degradation in optical properties
(decrease in solar absorptance and increase in emittance), as well as visual corrosion, were the criteria
used for establishing the panel durability.
All optical measurements were made with a portable Gier Dunkle Solar and IR Reflectometer.
The solar energy absorptances were determined by computing the difference between the solar energy
reflectance and unity; the emittances were determined similarly by computing the differences between
the 1R reflectance and unity.
DISCUSSION AND RESULTS
Rural Environment
This exposure site, located at MSFC near Huntsville, Alabama, represents an environment that
is low in, or essentially free from, the common pollution agents normally present in industrial or sea-
coast areas (such as hydrogen sulfide, sulfur dioxide, ammonia, nitrite, chlorides) that accelerate the
corrosion of metals. The test rack and general area are shown in Figure 2.
Duplicate "Roll-Bond" panels plated with black chromium were exposed to this environment
for a total of 60 months, positioned at a 45-degree angle facing south as shown in the figure. The
results of the tests showed that the panels had excellent corrosion resistance to this environment. At
the end of the test period, some minute specks surrounded by small areas of discoloration were
present. but this condition had no significant effect on the optical properties. A representative test
panel after 60 months exposure is shown in Figure 3. The optical properties (average of duplicate
panels) before, during, and at the end of the test period are shown in Table I. As shown in the
table, no change in the solar energy absorptance had occurred at the end of the test; and the emitt-
ance had increased only slightly.
Seacoast Environment
This test site, located at Kennedy Space Cer ter near Titusville, Florida, represents an environ-
ment which causes extremely high corrosivity because of the sea spray. Test specimens were exposed
for a total of 13 months at two different locations in this area: (1) approximately 120 ft from the
mean high tide line and (2) 1 mi inland. The panels were mounted at a 30-degree angle on racks
that were facing the ocean in an easterly direction. A typical rack is shown in Figure 4.
At the end of the test period, the panels showed a considerable amount of corrosion; but the
optical properties were not severely degraded. Corrosion in the form of small gray to white pits was
observed on the panels located on the beach a few days after the initiation of the test. Similar pits
were observed on the panels located 1 mi inland about 4 weeks after exposure. After 13 months, the
panels at both sites were covered with numerous spots of white corrosion ranging from approximately
2
0.32 cm to 0.48 cm (0.13 in. to 0.19 in.) in size, but, as expected, were more numerous on those
located on the beach. The black chrome and nickel coatings were lifted from the substrate in most
of these corroded spots. Representative test panels are shown in Figure 5, and the optical properties
(average of duplicate panels) are shown in Table 2. Table 2 shows that no significant change occurred
in the solar energy absorptances, but the emittances showed a slight increase in the case of the panels
located I mi inland and a moderate increase in the case of those on the beach site. Overa!l, the
optical degradation was not considered severe. However, in view of the amount of corrosion present
on the panels, severe degradation would be expected to occur soon.
Industrial Environment
This test site, located at ACIPCO in the northern section of Birmingham, Alabama, represents
in area that is highly industralized. A test specimen, mounted on a rack designed to hold it at a
45-degree angle, was located on the top of a multi-story office building at ACIPCO where it remained
exposed to this environment for a period of 36 months. Figure 6 shows the rack and pan':l at the
test site facing a southerly direction at the initiation of the test.
The results of the test showed the black chromium hud good resistance to this industrial
environment. At the end of the test period, the solar energy absorptance showed a slightly favorable
increase; but the emittance also increased slightly, indicating a degradation in this property. This
.mall change, in either case, was not considered significant. The optical data are shown in Table 3.
In appearance, the most significant change was the presence of numerous small brown spots scattered
over the entire panel surface. This appeared to have resulted from the deposition of minute cinder
particles onto the surface of the panel where they clung to the surface to form brown to red rust.
'these particles were apparently emitted from the ACIPCO metal furnaces. The brown spots covered
the entire panel surface, but were very small, rangin3 from approximately 0.04 cm to 0.09 cm (0.02
in. to 0.03 in.) in diameter. The test panel, at the end of the exposure period, is shown in Figure 7.
CONCLUSIONS
Corrosion was most severe on the seacoast panels, even though they were exposed for a shorter
period of time. The durability of the coating system in the rural and industrial environment -,as
much greater than in the seacoast environment, as was expected. The aggressiveness of the environ-
ment in the ACIPCO and the northern Birmingham area was not as great as expected. The panels
exposed to this environment were only slightly more corroded and optically degraded in 36 months
than the panels exposed to the rural environment in 60 months. Considering the rate of degradation
in the final 12 months of exposure, severe degradation in the ACIPCO environment for an additional
4	 24 months would not be anticipated. Based upon the results of these tests and the conditions under
which they were accomplished, it can be concluded that this coating system has exceptionally good
optical durability in each of the environments.
3
Atmospheric exposure test racks, located at MSFC.
ORIGINAL PAGE
BLACK AND WHITE PHOTOGRAPH
FLON►AS"I OtTAII
1.91 M
17 hl
t	 1
1.l^ ^w N.N iwl
0.32 so	 II iw
Lft so 4.376 iwl
I
SAI M
^	 y laft)
1(	Figure 1. "Roll-Bond" panel design.
mospheric exposure racks located on the beach at KSC.
ORIGINAL' PAGE
BLACK AND WHITE PHOTOGRAPH
Figure 3. Nickel-Black chromium electroplated "Roll-Bond" panels after atmospheric
exposure at MSFC, exposure time 60 months.
5
BEACH
INLAND
roplated "Roll-Bond" panels after atmospheric
:xposure time 13 months.
CMGMAL PACE
BLACK AND WHITE PHOTOGRAPH
-A
fLill
CI
ci
^I
^i
L
I I it u,e e.. Atnlo,phcrlc rxl,u,urr site, located at the top of an office building at
ACIPCO in lilrn Ingham, Alabama.
Figure 7. Nickel-black chromium electroplated "Roll-Bond" panels after atmospheric
exposure at AC HIM in Birmingham, Alabama, exposure time 36 months.
7
"TABIT' I EFFECT OF RURAL OUTDOOR ENVIRONMENT ON THE: SOLAR ENERGY
ABSORPTION CHARA("I T ERIS"TICS OF BLACK CHROMIUM
01),,w1
1'1opettics
Before
Exposure
Exposure Time	 Months
3 9 21 29 38 47 55 6G
Absorptance 0.90 U.96 U.94 0.96 U.94 0.94 0.94 U.90 0.96
I	 niitt.utce O.U8 0.08 0.08 0.08 0.10 0.09 0.11 0.10 0.10
I ANLI. 2. EFFECT OF SFACOAST ENVIRONMENT ON I'll[- SOLAR ENERGY
ABSORPTION CHARACTERISTICS OF BLACK CHROMIUM
Exposure
Time
Months
Before
Optical Properties Exposure 1	 13
Beach
Absorptance 0.94 0.96	 0.93
Emittance 0.11 0.12	 0.28
1 mi Absorptance 0.95 0.97	 0.94
Emittance 0.09 0.08	 0.13Inland
TABLE 3. EFFECT OF AN INDUSTRIAL ENVIRONMENT ON THE SOLAR ENERGY
ABSORPTION CHARACTERISTICS OF BLACK CHROMIUM
Optical
Properties
Before
Exposure
Exposure Time --- Months
2 9.5 13.6 26.5 36
Absorptance 0.93 0.94 0.89 0.92 C.93 0.96
Fntittance 0.09 0.10 0.13 0.12 0.17 0.14
♦ ,
OF 
H
REFERENCES
Lowery, James R.. Solar Fuleigy Absorption Characteristics anti the Effects of Nkat on the
Uptiral Properties of Several Coatings. George C. Marshall Space Flight Center, NASA TM-
82414, April 19H I .
George C. Marshall Space Flight ('enter, "The Development of a Solar-Powered Residential
Ileating and Cooling system" , May 10, 1974.
9


Environmental durability of electroplated black chromium

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