Corrosion Mechanisms and Cosmetic Corrosion Aspects of Zinc-Aluminium-Magnesium and Zinc-Chromium Alloy Coated Steel Strip

摘要

Corrosion mechanisms and cosmetic corrosion behaviour of Zn-AI-Mg alloy coating (ZM/HDG) and Zn-Cr alloy coating (ZCE/EG) in comparison to conventional zinc coating (Z/HDG) are presented.The outstanding corrosion protection performance of the new zinc-alloy type coatings is based on the formation of special corrosion inhibiting layers. In the case of ZM/HDG the nature of the corrosion product layer is based on Hydrotalcite. Up to six fold corrosion protection was observed even with half of the coating thickness of ZCE/EG coatings and paint creepage is reduced down to 50% in comparison to conventional zinc coatings (Z/HDG, ZE/EG).This clear improvement in corrosion protection is surely one of the most important product properties.