Effect of Zn content on corrosion resistance of as-cast Al-6Si-3Cu alloy

• Proper Zn addition improves the corrosion resistance of as-cast Al-Si-Cu alloy. • Excessive Zn addition enhances the tendency of Si phase as a cathode. • Adding ~1% Zn to Al-6Si-3Cu alloy reduces the corrosion rate by 19.8%. In order to improve the corrosion resistance of as-cast Al-Si-Cu alloy, in this work, the effects of Zn content are investigated by using SEM, EDS and electrochemical studies. The results show that with Zn content increasing, the corrosion resistance of Al-6Si-3Cu alloy first becomes stronger and then weaker. The alloy with 0.97 wt% Zn exhibits the best corrosion resistance. Its corrosion rate is lower than that of Al-6Si-3Cu alloy. The addition of Zn produces a Zn-rich area around Al 2 Cu phase and weakens the corrosion process between Al 2 Cu phase and Al matrix. However, excessive Zn addition changes the morphology of Al 2 Cu phase and makes it act as electron transfer channel between Si phase, which shows a negative effect on corrosion resistance.