Evaluations of microstructure and electrochemical characteristics of Al-Si-Cu/clay nanocomposites in two corrosive solutions

Abstract

Effects of manufacturing parameters on the electrochemical properties of aluminum-based nanocomposite with clay reinforcement have been investigated as a new study. Tafel polarization and electrochemical impedance spectroscopy tests at ambient temperature and in two corrosive environments were used to investigate the characteristics of the fabricated nanocomposites. Examination of different specimen microstructures was performed by optical and scanning electron microscopy before and after electrochemical tests. Electrochemical measurements indicated that nanocomposites had a higher corrosion rate in 0.6 M NaCl solution compared to the Al-Si-Cu matrix. The lower content of the Si and AlCu4 precipitates was a major parameter in reducing corrosion attacks. However, nanocomposites exhibited a higher corrosion resistance in comparison with the aluminum matrix in 0.02 M H3BO3 solution. Such an increase range was about 25.3–70.3 % concerning nanocomposites. The highest resistance was attributed to the nanocomposite stirred for 2 mins at 800 °C. In this situation, a higher content of Si precipitates (up to 30 %) with a small size was an effective factor in forming a passive layer at the matrix surface and acting as an obstacle for further corrosive ions diffusion toward the inner layer of the material.