A Comparative Investigation on corrosion Behaviors of High Pressure Die-cast Al-Si Alloys in 3.5% NaCl solution

High pressure die-cast aluminum-silicon (Al-Si) alloys have been widely used to produce the power battery shell for new energy vehicles, and their corrosion resistance directly affects the durability of the battery. In this study, the corrosion behaviors of the high pressure die-cast AlSi10MgMn and AlSi9MnMoZr alloys were studied systematically for the first time by electrochemical, salt spray and immersion tests, and compared with the A356.2 and A380 alloys. The results indicated that all Al-Si alloys were composed of α-Al matrix and single-phase pure Si phase, while the presence of the Al15(FeMn)3Si2 phase and Al12Mn3Si2 phase was discovered in the AlSi10MgMn alloy and the AlSi9MnMoZr alloy, respectively. The potential of those phases was similar to that of the matrix, which made them better corrosion resistance. Potententiodynamic polarization studies revealed that the AlSi10MgMn and AlSi9MnMoZr alloys had obvious passivation regions compared with the A356.2 and A380 alloys. Salt spray and immersion test results showed that the AlSi9MnMoZr alloy had the lowest corrosion rate in the early period of the tests. Thus, the AlSi9MnMoZr alloy has the best corrosion resistance among the four alloys and is the ideal high pressure die-cast Al-Si alloy for power battery shells.