Method for producing a solar selective coating on aluminum

摘要

An improved process for producing a solar selective coating on aluminum comprises a preliminary treatment such as an etch or brightening followed by anodizing in phosphoric acid at a constant voltage of from 10-20 volts for a time period sufficient to provide a total current of from 90-175 coulombs per square decimeter of aluminum surface. Prior to sealing, the resultant anodized surface is subjected to a constant AC voltage coloring treatment in a concentrated metal sulfate solution containing at least 85 grams per liter of metal sulfates.