Anodic oxidation of aluminium - giving coloured, high corrosion resistant surfaces

摘要

A method for coloured anodic oxidation of Al and Al alloyl using aq. baths as in DT 1913574.1 contg. 2.5-10 wt.% (pref. 6-8 wt.%) maleic acid and/or anhydride, 0.5-3.5 wt.% (pref. 1.5-2.5 wt.%) 4-sulphopthalic acid and/or 5-sulphoisophthalic acid and/or 3-sulphophthalic acid, 0.5-1 wt.% sulphuric acid and/or an equivalent amount of metal, ammonium or metal ammonium sulphate w.r.t. H2SO4 content at r.t. and 0.5-5.0 A/dm2. The method provides smooth, hard, highly corrosion resistant oxide surface coatings ranging from brown to black.