The only suitable black finish which would come close to meeting these requirements would be oxide black, produced by heating the parts at 1550-2200'F, for about 4-5 min. If the high temperature is not permissible, another alternative, although a more complicated one, is black chromium plating. This of course, will require a plating installation. In either case, the metal surface can be matted by abrasive blasting or by immersion in a solution of equal parts of 42' Baume ferric chloride and hydrochloric acid.
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