Current Developments in Improving the Corrosion Resistance of Zinc Coated Steel Sheets

Abstract

Practical experience and theoretical interpretation on the role of alloying elements on corrosion resistance are the main themes of this paper. Theoretically all the cathodic alloying elements in zinc coatings are expected to improve the corrosion resistance of the coating. However, lab studies and field exposure tests show that it is true only when the cathodic alloying is to a considerable extent. A microalloying, rather has deleterious effect on the corr-osion resistance of zinc coatings. It is further shown that a judicious combination of alloying elements have considerable influence on corrosion resistance of the coatings. A great deal of mismatch is observed between the lab and field exposure data. It is shown that a proper method of lab evaluation technique to indicate the actual performance of zinc coatings is very much required for development of future corrosion resistant zinc coatings. In addition to these aspects the paper also describes the future scopes for developments on this area.