A new study on the effects of clay nanoparticles on the corrosion performance of Al-Si-Cu matrix composites in both acidic and alkaline solutions

Abstract

In this paper, the influence of clay nanoparticles on the corrosion properties of the Al-Si-Cu matrix was investigated. The nanocomposite fabricating method was stir-casting when stirring times and temperatures were variables to change nanocomposite characteristics. Several corrosion tests were performed to examine the relationship between the microstructure and the degradation mechanism of various fabricated nanocomposites. Tafel polarization measurements indicated a lower corrosion rate for all nanocomposites compared to the Al-Si-Cu matrix in 0.1 M NaOH solution. The reduction range was 23.6–79.0% based on the smaller size of Si precipitates. In this situation, the interconnection of surface pores was lowest. However, electrochemical impedance spectroscopy (EIS) results showed that nanocomposite impedance would be increased up to 99.7% in comparison to the matrix without clay nanoparticles in 1 M HCl solution when the stirring temperature was 750 °C. EIS calculation also displayed that an increase (about 17.1–50.8%) in the nanocomposite resistance would be achieved when the stirring time was 2 min in 0.04 H2SO4 solution. The reason could be attributed to the larger size of Si particles since coarse precipitates were more effective agents to act as barriers for anodic dissolution of the lower layer of the Al-Si-Cu matrix when Tafel polarization tests demonstrated that the anodic reaction controlled the corrosion rate of the aluminum matrix.