Effect of adding rare-earth cerium on the microstructure and acid rain corrosion resistance of the ADC12 alloy

The effect of adding cerium on the microstructure and acid rain corrosion resistance of the AlSi11Cu3 alloy was investigated by means of optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. The AlSi11Cu3 alloy was doped with varying stoichiometries of cerium to generate AlSi11Cu3- x Ce, where x = 0, 0.5, 1.0, and 1.5 wt.%. The results show that the α-Al, eutectic Si, and β-Al${}_5$FeSi phases in the AlSi11Cu3-1.0Ce alloy are significantly refined. Electrochemical tests demonstrated an increase in the self-corrosion potential value of the AlSi11Cu3-1.0Ce alloy from –670 mV to –628 mV relative to the untreated alloy. In addition, the AlSi11Cu3-1.0Ce alloy has the lowest corrosion current density (8.4 μA · cm${}^{-2}$). Immersion corrosion testing on the AlSi11Cu3-1.0Ce alloy revealed a corrosion rate of 0.71 mg · cm${}^{-2}$ · d${}^{-1}$, constituting a 72% reduction in the corrosion rate compared to the untreated alloy. These results indicate that the AlSi11Cu3-1.0Ce alloy has a high resistance to acid rain corrosion, which is the result of a refinement of the cathode phases.