Development of a new organic composite coating for enhancing corrosion resistance of 55% Al–Zn alloy coated steel sheet

A new organic composite coating for enhancing corrosion resistance of 55% Al–Zn alloy coated steel sheet has been developed. The new coating is composed of an insoluble chromic compound, phosphate, organic resin and specially developed corrosion-preventive additives, which effect a self-healing action in cracks generated on the surface of the steel sheet while forming. This coating is superior to usual products with inorganic chromate coating and organic resin coating in corrosion resistance of flat and formed part, good appearance and chromium insolubility.