Variable anodic thermal control coating

A method of providing a thermal control coating on an aluminum or aluminum alloy surface with the coating having selected values within the ranges of 0.10 to 0.72 thermal emittance (.epsilon..sub.T) and 0.2 to 0.4 solar absorptance (.alpha..sub.s) comprising the steps of

• providing an aluminum or aluminum alloy material having a thickness of at least 0.001 inch and a surface area thereon adapted to be subjected to elevated temperatures;
• cleaning the surface area by immersion in a metal cleaning bath at a temperature of 160.degree. F. to 200.degree. F. for five to ten minutes;
• removing the surface from the cleaning bath and rinsing in a room temperature water bath;
• placing the surface in a deoxidixer solution at a temperature of 150.degree. F. for two to five minutes;
• removing the surface from the deoxidizer solution and rinsing in a room temperature water bath with surface agitation to remove all particulates from the surface;
• drying the surface by forced filtered air and measuring the initial thermal emittance and solar absorptance at this point;
• immersing the dried aluminum surface in a chromic acid solution;
• applying a controlled voltage between the surface and the chromic acid solution at a rate and for a period of time required to provide an anodized coating on the surface exhibiting the desired thermal emittance and solar absorptance respective ranges of 0.10 to 0.72 and 0.2 to 0.4.