The role of texture and morphology in optimizing the corrosion resistance of zinc-based electrogalvanized coatings

Abstract

Zinc-based electrogalvanized coatings have attracted increasing interest from the automobile industry and steelmakers because of their excellent corrosion resistance and good mechanical properties. The coating properties are closely related to the microstructure of electrodeposits. Texture is an important factor which influences the coating properties. This study demonstrates a relationship between the corrosion behavior of the electrogalvanized zinc, zinc-iron, and zinc-nickel coatings and their microstructure. Corrosion behavior is analyzed by the Tafel extrapolation method from the potentiodynamic polarization curves. In this study, it is found that the texture of coatings strongly influences corrosion resistance. The coatings with strong {0001} texture have better corrosion resistance than the coatings with weak {0001} texture or a {101X} fiber texture. The influence of alloy content and phase composition upon corrosion behavior is also discussed. Consequently, methods are proposed for optimizing the deposition process to obtain the desirable texture, morphology and alloy content of the deposit for better corrosion resistance.