GB1175143A - Decorating anodized metals or alloys, especially aluminium. - Google Patents

Abstract

1,175,143. Colouring anodized surfaces. MARTIN-MARIETTA CORP. March 21, 1967 [March 29, 1966], No.13219/67. Heading C7B. Anodized metal or alloy, e.g. Al, A1-Mg-Si or Ti, is coloured e.g. black by impregnating e.g. spraying a porous anodized layer on the metal or alloy with an aqueous solution containing both a precipitant ion donor, preferably a sulphide donor such as sodium, potassium or ammonium thiosulphate, thiourea or a substituted thiourea, and a metal ion capable of forming a coloured precipitate with the precipitant ion, e.g. Co, Cu, Sb, Ni, Mo, Fe, Cd or Bi ion, and then heating the impregnated anodized layer at a temperature above 120‹C., e.g. 121‹C. to 593‹ C., for at least 1 minute, effective to form the coloured precipitate. The solution may also contain NaHS0 3 or KHSO 3 as stabilizer; a thickening agent, e.g. a colloidal suspension of boehmitetype aluminium oxide, soluble starches, hydroxy alkyl celluloses, polyvinyl alcohol, polyacrylamide, methyl vinyl ether copolymer with maleic anhydride, polyvinylpyrrolidone or an ethylene oxide polymer; and a finely divided inert substance as flattening agent, e.g. Ti0 2 , rouge (Fe 2 O 3 ), ground mica, fine stabilized clay. The metal ion may be added as chloride. For Mo ion, (NH 4 )6 Mo 7 O 24 may be used. For corrosion protecting, anodized and coloured aluminium may be treated with aliphatic compounds, lacquers, waxes, boiling water, heated aqueous salt baths e.g. of sodium dichromate or nickel acetate. The anodizing may be effected in an aqueous bath containing 4-30% by weight H 2 SO 4 using an anodic C.D. of 2À1-108ma/cm<SP>2</SP>.