THE ROLE OF TEXTURE AND MORPHOLOGY IN OPTIMIZING THE CORROSION-RESISTANCE OF ZINC-BASED ELECTROGALVANIZED COATINGS

Zinc-based electrogalvanized coatings have attracted increasing intere st from the automobile industry and steelmakers because of their excel lent corrosion resistance and good mechanical properties. The coating properties are closely related to the microstructure of electrodeposit s. Texture is an important factor which influences the coating propert ies. This study demonstrates a relationship between the corrosion beha vior of the electrogalvanized zinc, zinc-iran, and zinc-nickel coating s and their microstructure. Corrosion behavior is analyzed by the Tafe l extrapolation method from the potentiodynamic polarization curves. I n this study, it is found that the texture of coatings strongly influe nces corrosion resistance. The coatings with strong {0001} texture hav e better corrosion resistance than the coatings with weak {0001} textu re 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 t he desirable texture, morphology and alloy content of the deposit for better corrosion resistance. (C) 1998 Published by Elsevier Science Lt d. All rights reserved.