SURFACE TREATMENT OF STEEL PLATE COATED WITH ALUMINUM BY HOT DIPPING

摘要

PURPOSE:To enhance the corrosion and slipping resistances of a steel plate coated with Al by hot dipping by forming a chromate film contg. a prescribed amount of Cr on the plate and by carrying out surface treatment with a prescribed organosilicon water repellent. CONSTITUTION:A chromate film having 5-40mg/m<2> total Cr content is formed on a steel plate coated with Al by hot dipping. A treating agent is prepared by adding silica sol to an organosilicon water repellent of silicone oil emulsion type, silicone varnish emulsion type or silicone varnish type so as to adjust the amount of SiO2 to 30-180% of the amount of silicon resin in the repellent. Said chromate film is treated with the treating agent to form an organosilicon film having 0.01-20mum thickness on the surface of the chromate film. Thus, a surface with superior corrosion and slipping resistances is obtd.