CHROMATE-ORGANIC PRE-TREATED STEEL FOR HIGH CORROSION RESISTANCE AND IMPROVED PAINTABILITY

摘要

A process of applying additional coatings to zinc coated steel or zinc alloy coated steel to improve at least the corrosion resistance and paintability of zinc or zinc alloys coated steel, comprises: Applying to the zinc or zinc alloy coated steel a first composition comprising an aqueous emulsion of an organic acrylic polymer in a chromic acid solution to form a first additional coating; and Subsequently applying to the steel a second composition, being an aqueous composition comprising a polyurethane polymer, one or more crosslinking agents and one or more silicates, to form a second additional coating.