Properties of Newly Developed Chromate Free Coated Hot Dip Galvanized Steel Sheet

by Akira Matsuzaki, Nobue Fujibayashi, Satoru Ando

Publisher - JFE Steel Corporation

Category - General Novel

In reply to the social requirement of eliminating hexavalent chromium, a variety of chromate-free coated galvanized steel sheets have been developed with various functions. Because of organic compounds contained in coated layers, some of the coated steel sheets have poor resistance to heat discoloration. We have developed a new inorganic type chromate-free coated hot-dip galvanized steel sheet. This product has superior performances for applications which require corrosion resistance and are exposed to high temperatures, due to its reduced vulnerability to heat discoloration. This paper describes properties of this new product such as corrosion resistance of flat and worked portions, spot weldability and coating appearance after heating. Comprised primarily of inorganic compounds, the chromate-free coating shows little discoloration from exposure to high temperature. An electrode tip life test revealed that spot weldability of this product is almost the same as that of chromate coated hot-dip galvanized steel sheet. This product also showed good white rust resistance in a salt spray test despite the thin coating layer suitable for weldability

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