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

Abstract

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.