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The effects of T6 heat treatment and 0.6 wt% (Pr+Ce) addition on microstructure, microhardness, and corrosion of AlSi5Cu1Mg alloy were investigated. Optical microscopy and scanning electron microscopy revealed that the T6 heat treatment and the addition of 0.6 wt% (Pr+Ce) effectively refined the α-Al and eutectic Si phases, which were uniformly distributed with Al 2 Cu phase in the alloy. Microhardness, weight loss, hydrogen evolution, Tafel polarization, and EIS tests showed that the combination of T6 heat treatment and 0.6 wt% (Pr+Ce) addition resulted in the best corrosion resistance and microhardness of the alloy. The microhardness of the AlSi5Cu1Mg+0.6 wt% (Pr+Ce)/T6 (115 HV) was 27.8% higher than that of the matrix (90 HV). At the same time, the corrosion current density of the alloy also reached the minimum value (38.4 μA cm −2 ). The T6 heat treatment and the addition of (Pr+Ce) can significantly decrease the average grain size, change the redistribution of the precipitated Al 2 Cu phase, refine the Si phase, and increase the pitting formation position, thus reducing the sensitivity of exfoliation corrosion.

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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-xCe, where x = 0, 0.5, 1.0, and 1.5 wt.%. The results show that the α-Al, eutectic Si, and β-Al5FeSi 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.