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

Through the heat treatment process of pre-alloying and then austenitizing, the effect of austenitizing on the microstructure and corrosion resistance of Al-10Si-xZn-yMg 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 Fe3Al phases appeared in the coating. Moreover, as the austenitization time increased, the volume of the FeAl phase became bigger, and the volume of the Fe2Al5 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.