SELF-HEALING ABILITY OF ZINC-PLATED STEEL COATED WITH MAGNESIUM ELECTRODEPOSITED FROM A MOLTEN-SALT

In order to clarify the reason for the excellent corrosion resistance of zinc-plated steel coated with magnesium which was electrodeposited from a molten salt, corrosion products in a 5 mass%NaCl aqueous soluti on were investigated by X-ray diffraction analysis and EPMA. It was fo und that thin MgO layer was rapidly formed on the surface and acted as a protective film. It was also found that thin MgO layers were formed along the cracks in the zinc-plated layer, and stopped up the cracks and prevented corrosion from proceeding through the cracks. The latter fact means that the magnesium-containing zinc-plated layer has a self -healing ability.