The influence of porosity and precipitates on the corrosion behavior of A356 aluminum alloy

Abstract

In this article, the pore and precipitation phases of A356 aluminum alloy were regulated by adding element Cu, and the corrosion kinetic behavior was investigated by electrochemical experiments and salt spray test (SST), while the corrosion mechanism of A356 aluminum alloy was studied by scanning electron microscopy (SEM), 3D laser confocal microscopy (LSCM) and atomic force microscopy (SKPFM). The results of both electrochemical and salt spray experiments showed that the corrosion rate increased with increasing Cu content, and the average corrosion rate increased from 0.040 mm y-1 to 0.329 mm y-1 when the Cu content increased from 0 wt% to 7 wt%, and the Cu free alloy exhibited a greater charge transfer resistance. This is mainly due to the addition of Cu on the one hand to increase the number of precipitation phase, Al2Cu become the main precipitation phase, SKPFM test results show that the precipitation phase relative to the Al matrix potential difference in order: Al2Cu (350 ∼ 380 mV), Si (250 ∼ 275 mV), Mg2Si (80 ∼ 110 mV), the increase in potential difference between the two phases to promote the corrosion of occurrence. On the other hand, CT results showed that the average diameter of pores increased from 89.95 µm to 281.00 µm, and the volume fraction increased from 0.05 % to 0.18 %, and the larger and more porous pores help promote corrosion. Therefore, how to control the porosity and precipitation phase is an important factor in regulating the corrosion behavior of A356 aluminum alloy.