A metal oxide coating is plated onto a metal substrate at the cathode from an acid solution which contains an oxidizing agent. The process is particularly useful for producing solar panels. Conventional plating at the cathode avoids the presence of oxidizing agents. Coatings made in accordance with the invention are stable both at high temperatures and while under the influence of high photon flux in the visible range

Mcdonald, G. E.

English

NASA Technical Reports Server

4,350,574 
McDonald [45] Sep. 21, 1982 
[111 United States Patent [I91 
1541 METHOD FOR DEPOSITING AN OXIDE 
COATING 
[75] Inventor: Glen E. McDonald, Strongsville, 
4,094,750 6/1978 Mackey ............................. 204/56 R 
4,111,760 9/1978 Chen et al. ............................ 204/48 
4,239,604 12/1980 Mahdjuri .......................... 204/56 R 
4,296,182 10/1981 Matsubayashi et al. .............. 204/51 
Ohio 
Primary Examiner-R. L. Andrew 
Attorney, Agent or Firm-Norman T. Musial; John R. 
~ ~ ~ ~ i ~ ~ ;  G~~~ E. Shook 
[73] Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 1571 ABSTRACT 
[21] Appl. No.: 246,772 According to the invention a metal oxide coating is 
[22] Filed: Mar. 23, 1981 plated onto a metal substrate at the cathode from an 
acid solution which contains an oxidizing agent. The 
process is particularly useful for producing solar panels. [51] Int. (3 .3  C25B 1/02 
[58] Field of Search ...................................... 204/56 R ~onventional Plating at the Cathode avoids the Presence 
of oxidizing agents. Coatings made in accordance with 
~561 References Cited the invention are stable both at high temperatures and 
while-under the influence of high photon flux in the 
................................................ 
[52] U.S. (3. .................................................. 204/56 R 
U.S. PATENT D 
2,733,199 VI956 Wick ..... ........ 204/56 range* 
49080,269 311978 Scholz et al. ..................... 204/56 R 
2,844,530 2/1958 Wesley et al. ........................ 204/40 
3,723,261 311973 Byers et al. ........................... 204/51 
4 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=19830002224 2020-03-21T23:21:07+00:00Z
4,350,574 
1 2 
A process for depositing an oxide layer from a solu- 
tion containing a metal salt and isopropynol is disclosed 
in Mackey U.S. Pat. No. 4,094,705. The patent fails to 
mention the solar absorption properties of the oxide 
Schardein et a1 U.S. Pat. No. 4,104,136 describes a 
METHOD FOR DEPOSITING AN OXIDE 
COATING 
ORIGIN OF THE INVENTION 5 layer. 
The invention described herein was made by an em- 
ployee of the United States Government and may & 
manufactured and used by or for the Government for 
process for 
for 
thin 'Oatin@ to a substrate 
energy absorption* The process provides for 
electrochemically plating a clean aluminum surface in a 
DISCLOSURE OF INVENTION 
According to the present invention the metal coating 
is oxidized as it is deposited. This produces a black 
An appropriate quantity of an oxidizing agent is 
governmental purposes without the payment of any 
royalties thereon or therefor. 
TECHNICAL FIELD 
10 solution containing ammonium molybdate. 
This invention is concerned with coating a substrate 
with a black metal oxide film that is highly absorbing. 15 metal oxide film that is highly absorbing. 
The invention is particularly directed to an improved 
tors. 
sion to heat and electrical power. These devices utilize 2o avoids the presence of oxidizing agents. 
flat panels to collect the energy. 
It has been suggested that the heating panels be selec- 
tively coated to increase the energy absorbing proper- 
ties. Such solar heating panels may be coated with black 
process for producing collec- added to a plating solution. The metal coating is then 
plated at the cathode. Such devices collect energy from the sun for conver- Conventional plating at the cathode rigorously 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
A metal substrate to be coated in accordance with the 
paint which is inexpensive and absorbs energy* 25 present invention may have any ofa number of different 
However* such a coating is not very because configurations. By way of example, the substrate may 
paint flake and paint much be a plate, bar, or tube. Also, the substrate may or may 
If there is no concern about emittance of the collector 
been used for solar heating panels* Black is a 30 but only with obtaining a stable, low cost, high & s o p  
good heat conductor, but coatings of this material are tance coating, then the metal oxide may be plated di- 
chrome loses some Of its rectly onto the substrate. If both high absorptance and 
stability at high operating temperatures. low emittance are desired, metal oxide may be 
ust have h has low emittance. 
high absorptance in the visible range and low emittance 35 Also in this situation the coating may be plated onto a 
in the infrared range for Optimum results. These coat- suitable low emittance foil. Further, the metal oxide 
should be stable both at high temperatures and coating may be electroplated on a coating which has 
while under the influence of high Photon flu% in the been deposited previously onto the metal substrate. 
visible range. The coatings should be able to be applied According to the present invention a metal oxide 
equipment in an ~Conomical man- 40 coating is plated onto the metal substrate at the cathode 
from an acid solution which contains an oxidizing 
have been used to Coat substrates agent. By way of example, a black cobalt oxide has been 
for use in solar h e a t h  Panels. However, many of these plated from a solution having the following composi- 
coatings were unsatisfactory because they were either tion at the listed parameters: 
not stable at solar collector operating temperatures or 45 
not have low emittance. of the absorbed energy to be lost by emittance. 
Coatings of both black nickel and black chrome have 
to moisture* 
The coatings used for solar heating pan plated on a metal substrate 
4 ounces/gal. of cobalt sulfate 
6 ounces/gal of cobalt chloride 
5 ounces/gal of boric acid 
PH of 3.5 
S. Pat. NO. 2,733,199 discloses a process for Temperature of 115" F. 
ly depositing chromium films on metal from a 50 Current density-& amps/sq. ft. 
solution while Wesley et al U.S. Pat. No. 2,844,530 An oxidizing agent, such as 10 mlniter of 30 percent 
position of a black nickel coating Hz02, is added to the solution and plated for a sufficient 
time to produce an oxide coating of 1 to 2 micrometers. 
U.S. Pat. No. 2,917,817 to Tabor is directed to thin Practices known to the trade in creating a uniform 
exposed light absorptive and heat transparent surface 55 current density across the surface are utilized. Also, an 
coatings, which are in heat conductive relation to a addition of plating assisting agents, such as wetting or 
bright metal base. Solar heating panels utilizing these surface tension adjusting agents, may be used. 
atings have been expensive and difficult to produce. Other oxidizing agents known to the trade may be 
McDonald U.S. Pat. No. 4,055,707 describes a black used. Also. other acids and/or buffers may be used for 
sive and difficult to apply. 
BACKGROUNDART 
chrome coating for solar panels which is electroplated 60 plating at the stated PH. It is contemplated these other 
onto a metal substrate. Several electroplating solutions materials may be used for plating at other PHs between 
are described in this patent. 1.0 and 6.0. 
Scholz et al U.S. Pat. No. 4,080,269 discloses a It is further contemplated that other concentrations 
ethod for producing a black coating which is highly of H202 may be used. Air agitation or mechanical agita- 
absorbant in the solar spectrum range using electrode- 65 tion of the solution may be desirable. Also, the plating 
may be performed in an unstirred solution. 
It is further contemplated that the cobalt may be 
d in varying amounts with other metals, or com- 
4,350,574 
3 4 
binations of other metals. These substitute metals in- 
clude, but are not limited to, nickel, chromium, manga- 
nese, and vanadium. These other metals can produce 
properties in the deposited oxide coating which may be 
mal stability. 
It is further contemplated that other current densities 
may be used to obtain certain desirable results. One 
tion of both high absorptance in the visible range and 
low emittance in the infrared range. 
While the preferred embodiment of the invention h a  
been described, it will be appreciated that various modi- 
ing from the spirit of the invention and the scope of the 
subjoined 
I claim: 
In a method of coating a substrate with a black 
current densities than black chrome can be deposited. selected from the group consisting essentially) of cobalt 
I+br to coating the metal substrate to be Plated is sulfate, about 6 ounces per gallon of cobalt chloride, 
suitably cleaned in accordance with known pratices. and about 5 Ounces per gallon of boric acid having PH 
The substrate is then rinsed with clean water and elec- 15 in the range between about 1.0 and about 6.0 at a tem- 
troplated at the cathode in the solution as aforemen- perature of about 115" F. (, nickel, chromium, and man- 
tioned. ganese) to form a solar collector that is highly absorb- 
The coatings produced in accordance with the de- ing, the improvement comprising 
scribed process are adherent and stable at temperatures adding an oxidizing agent to said Plating Solution, 
such as cobalt oxide, has high absorptance in the visible 
spectrum, m i s  absorptance may be 95 percent or 
higher. This absorptance is stable to temperatures in 
excess of 1200" F. 
The materials described for making the solution are 
much lower in cost than conventional electroplating 
solutions required to produce conventional electro- 
plated coatings. 
process is that control of the current density produces a 
black coating of sufficient thicluless to be highly absor- 
bant, and it can be produced on a surface of low emit- 
desired, such as altered absorptance spectrum or ther- fications may be made to the procedure without depart- 
advantage of the Process of the present invention is that 10 metal oxide film from an electroplating solution con- 
a deposit of an oxide can be produced at much lower taining about 44 Ounces per gallon (a s& of a metal 
higher than 1200" F. Certain of these oxide coatings, 20 mounting said substrate in Said Solution t0 form a 
cathode, and 
electrodepositing cobalt (said metal) from said solu- 
tion onto said substrate at said cathode by passing a 
current of about 40 amps per square foot of sub- 
strate therethrough while simultaneously oxidizing 
the same. 
2. A method as claimed in claim the oxi&- 
ing agent is H ~ ~ ~ .  
3. A method as claimed in claim 2 wherein 10 ml/liter 
Another beneficial technical effect resulting from this 30 of 30 percent ~~0~ is added to the electroplating solu- 
tion. 
4. A method as claimed in claim 1 wherein the elec- 
troplating solution has a PH of about 3.5. 
25 
tance in the required thicknesses to have the combina- * * * * *  
35 
40 
45 
50 
60 
65 
UNITED STATES PATENT OFFICE 
CERTIFICATE OF CORRECTION 
Patent No. 4 , 3 5 0 , 5 7 4  Dated September 21, 1982 
Inventor ) Glen E. McDonald 
It i s  c e r t i f i e d  that error appears i n  the above-identified patent 
and that said Letters Patent are hereby corrected as shown below: 
Claim 1, lines 11 and 12, cancel If(, salt of a metal selected 
from the group consisting essentially)" 
lines 16 and 17, cancel 'I (, nickel, chromium, and 
manganese) 
line 22, cancel It (said metal)" 
Signed and Sealed this 
Seventh 10 a y 0 f December 1982 
ISEALJ 
Attest: 
Attesting Officer 
GERALD J MOSSINGHOFF 
Commistrunrr o J Parents and Tmdemarhs 


Method for depositing an oxide coating

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