White chromate treatment an excellent way to paint performance and corrosion resistance

摘要

PURPOSE: To impart excellent corrosion resistance and coatability to nonferrous metal plated steel sheets or nonferrous metallic materials by forming chromate films by using a treating liquid having a specific compsn. ;CONSTITUTION: The compsn. of the chromate treating liquid to be formed is formulated to contain (a) 7.5 to 10g/l, in terms of chromic anhydride, reduced chromic acid of 3/7 to 7/3 compsn. ratio of Cr⁺³/Cr⁺⁶, (b) 0.5 to 3.0 phosphoric acid compd. by weight in terms of the chromic anhydride of the reduced chromic acid, (c) 0.5 to 5.0 silica and/or colloidal silica of silicate by weight in terms of the chromic anhydride of the reduced chromic acid and (d) 1.0 to 20g/l phosphonic acid or phosphate compd. This treating liquid is applied on the material surfaces and is dried by heating, by which the chromium films of 7.5 to 100mg/m² per one surface in terms of Cr are formed.;COPYRIGHT: (C)1995,JPO