Corrosion behaviour of hot-dip Al-Zn-Si and Al-Zn-Si-3Mg coatings in NaCl solution

The corrosion behaviour of hot-dip Al-Zn-Si and Al-Zn-Si-3Mg coatings on steel sheets in NaCl solution were investigated by microstructural characterization, weight loss tests, and electrochemical methods Localized corrosion of the Al-rich phase in the Al-Zn-Si coating was observed. The exposure of the intermetallic layer was supposed to present galvanic corrosion and remarkably accelerate the consumption of remnant Al-rich phase. The MgZn2 phase was detected in the interdendritic Zn-rich region of the Al-Zn-Si-3Mg coating. The presence of the MgZn2 and Mg2Si phases contributed to delaying the occurrence of localized corrosion.