Accession Number : ADD016274

Title :   Trivalent Chromium Conversion Coatings for Aluminum.

Descriptive Note : Patent, Filed 27 Sep 93, patented 19 Apr 94,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Pearlstein, Fred ; Agarawala, S

Report Date : 19 Apr 1994

Pagination or Media Count : 6

Abstract : Corrosion resistant coatings are formed on aluminum by immersion in aqueous solutions containing chromic salts, a fluoride ion from compounds such as a fluosilicate with an alkali added near or slightly beyond the precipitation of the insoluble basic compounds. Trivalent chromium films formed on the aluminum surface when tested in 5% NaCl salt spray chamber showed corrosion resistance in excess of 96 hours. After a posttreatment with peroxide or permanganate solutions, the corrosion resistance for the aluminum substrates exceeded 168 hours. Trivalent chromium coated aluminum serves as an effective base for paint primers. Anodized aluminums were also afforded excellent corrosion resistance, after being treated in dilute/basic chromic sulfate solutions and post-treated with peroxide.

Descriptors :   *ALUMINUM, *CHROMIUM, *COATINGS, *CORROSION RESISTANCE, *PATENTS, *VALENCE, CHAMBERS, CORROSION INHIBITION, FILMS, FLUORIDES, IMMERSION, IONS, PAINT PRIMERS, PAINTS, PERMANGANATES, PEROXIDES, PRECIPITATION, PRIMERS, RESISTANCE, SALTS, SPRAYS, SUBSTRATES, SULFATES, SURFACES, CONVERSION, WATER, LIQUIDS, SILICATES, ALKALI METALS, ANODIC COATINGS, METALS

Subject Categories : Inorganic Chemistry
      Coatings, Colorants and Finishes
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE