COLORLESS CHROMATE COATINGS FOR ALUMINIUM SURFACES

摘要

Colorless chromate film having good corrosion resistance and adhesive property on Aluminium, Aluminium alloy or Aluminium-coated steel when these materials are subjected to a pre-treatment stage wherein the material is rinsed with hot water after de-oiling and dried while the water film still lying on the surface is wiped by drawing rolls, a treatment stage wherein the material is processed with an aqueous solution of about 2 to 10g/l of CrO3, 0.05 to 1g/l Cr<+>3, 0.2 to 5g/l F<->, 0.01 to 5g/l of Ferricyanide and/or Ferrocyanide, 0.01 to 1g/l Al<+>3 and a post treatment stage wherein the material is processed with an aqueous solution containing water soluble copolymer of itaconic acid and acrylonitrile.