Effect of austenitization on microstructure and corrosion resistance of Al-10Si-xZn-yMg coating

Abstract

Through the heat treatment process of pre-alloying and then austenitizing, the effect of austenitizing on the microstructure and corrosion resistance of Al-10Si- x Zn- y Mg coating was investigated. After pre-alloying at 700 °C, the Al-Si alloy layer in the coating began to disappear. As the austenitizing temperature increased, FeAl and Fe 3 Al phases appeared in the coating. Moreover, as the austenitization time increased, the volume of the FeAl phase became bigger, and the volume of the Fe 2 Al 5 phase became smaller. The Si element and a small amount of Zn and Mg elements had always existed in the coating in the form of solid solution. The self-corrosion potential of Al-10Si and Al-10Si-10Zn-2Mg coatings after austenitization increased, while its self-corrosion current density first decreased and then increased, and was the smallest when the austenitizing temperature was 950 °C. Compared with Al-10Si coating, Al-10Si-10Zn-2Mg coating after austenitization at the same temperature had lower self-corrosion potential and self-corrosion current density. Therefore, the addition of Zn and Mg elements could improve the sacrificial protection and corrosion resistance of Al-10Si coatings. • Pre-alloying and then austenitizing were used in the heat treatment process. • Al-10Si- x Zn- y Mg coating after austenitizing was composed of Fe 2 Al 5 , FeAl and Fe 3 Al phases. • Zn and Mg elements dissolved in the Al-10Si-10Zn-2Mg coating after austenitizing. • Al-10Si-10Zn-2Mg coating can provide excellent cathodic protection for steel.