Understanding the corrosion behavior by passive film evolution in Zn-containing Al-Si-Cu cast alloy

The effect of Zn addition on microstructure and corrosion behavior of Al-6Si-3Cu alloy are investigated. The addition of Zn improves the corrosion resistance of T6-treated Al-6Si-3Cu-xZn alloy, and excessive Zn addition weakens it. The addition of 0.97% Zn increases the corrosion resistance of the alloy by increasing the thickness of passive film from 1.124 to 1.399 nm, producing Zn-oxide layer on Si phase and reducing the potential difference between Si and Al matrix from 0.83 to 0.67 V. The addition of excessive Zn increased the corrosion rate by adsorbing Zn ions into the passive film and making it porous.