Heat Treatment Effect on Corrosion Resistance of Mg Coating Film on Hot-Dip Aluminized Steel

Abstract

Magnesium was coated on a hot-dip aluminized steel plate by the physical vapor deposition process. The effects of intermetallic compounds formed by heat treatment and crystal orientation on corrosion resistance were investigated. Furthermore, corrosion resistance was evaluated through various electrochemical corrosion tests, and corrosion products were investigated as well. In the salt spray test, the heat-treated Mg film showed higher corrosion resistance than non heat-treated Mg film as well as hot-dip aluminized steel plate due to various intermetallic compounds and increased interplanar spacing of aluminum. Moreover, higher film resistance in heat-treated Mg was confirmed through electrochemical impedance spectroscopy. Based on the results, the corrosion mechanism of the heat-treated Mg was suggested where MgAl2O4 played a major role in shielding corrosion factors in the intermediate stage of corrosion. The heat-treated Mg showed a robust potential as an alternative corrosion-resistant film to replace hot-dip and electroplated film.