Coated surface withstands space environment with negilgible change in radiation characteristics and physical properties. Process can be used with any porous substance, as long as pores are large enough to allow molecules of reacting solutions to enter and yet not so large as to allow nickel sulfide to be leached out of pores before sealing

Progar, D. J.

English

NASA Technical Reports Server

NASA TECH BRIEF 
Langley Research Center S
August 1973
	 B73-10238 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Applying High-Emittance and Solar-Absorptance Coating to Aluminum 
.
A process has been developed at Langley Research 
Center for producing a surface coating which has a 
high, total hemispherical emittance and a high ab-
sorptance, over the 0.25- to 25-micrometer wavelength 
range, and a relatively flat spectral distribution. The 
values of emittance (covering the wavelength range of 
from 1 to 25 micrometers) and solar absorptance 
(covering the range of from 0.25 to 2.6 micrometers), 
obtained by the process to be described, are 0.93 and 
0.97, respectively. A surface coated in this manner is 
able to withstand the space environment (which includes 
high vacuum, ultraviolet radiation, micrometeoroids, and 
ionizing radiation) with negligible change in its radiation 
characteristics and its physical properties. 
This coating can be applied to aluminum or aluminum 
alloy as thin as 0.003 inch (0.076 mm), with negligible 
weight increase. 
The application of this coating process is accomplished 
in three steps: (1) the surface is anodized, (2) then it is 
dyed with inorganic nickel sulfide, and (3) the coating 
is sealed. 
The initial step is to clean the aluminum or aluminum 
alloy of surface contaminants, using standard techniques, 
The sulfuric acid method is then used for anodization 
under the following conditions: 
Electrolyte - 15% sulfuric acid; 
Current density - 0.01725 A/cm2; 
Temperature - 302 to 305 K; and 
Time - 45 to 120 minutes. 
This produces a coating of aluminum oxide which is a 
highly porous, noncrystalline honeycomb film. 
The second step involves formation of nickel sulfide 
by reacting two different solutions inside the pores of 
the film. To accomplish this, the anodized aluminum is 
placed in a solution of nickel acetate (50 gIl, pH of 6) at
room temperature for 2-3 minutes. It is immediately 
immersed into concentrated ammonium hydrosulfide 
for 2-3 minutes and then rinsed in demineralized or 
distilled water. This cycle is repeated three or four 
times, or until the material is black. 
The coating is sealed by placing the dyed anodized 
material into water for a period of 10 minutes. The water 
should be at a temperature between 90.5 0 and 93.30 C 
and have apH of 5.5 to 5.8. 
This process can be used with any porous substance, 
as long as the pores are large enough to allow the 
molecules of reacting solutions to enter and yet not so 
large as to allow the nickel sulfide to be leached out of 
the pores before sealing. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Langley Research Center 
Mail Stop 139-A 
Hampton, Virginia 23665 
Reference: B73-10238 
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Patent Counsel 
Langley Research Center 
Code 456 
Hampton, Virginia 23665 
Source: Donald J. Progar 
Langley Research Center
(LAR-1015 1) 
Category 04, 08 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
.
https://ntrs.nasa.gov/search.jsp?R=19730000238 2020-03-17T07:15:42+00:00Z


Applying high-emittance and solar-absorptance coating to aluminum

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