Electrochemical investigation of the corrosion behavior of heat treated Al-6Si-0.5Mg-xCu (x=0, 0.5 and 1) alloys

Abstract

The corrosion behavior of heat treated Al-6Si-0.5Mg-xCu (x=0, 0.5 and 1 wt %) alloys in 0.1 M NaCl solution was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization curves reveal that 0.5 wt % Cu and 1 wt % Cu content alloys are less prone to corrosion than the Cu free alloy. The EIS test results also showed that corrosion resistance or charge transfer resistance (R_ct) increases with increasing Cu content into
Al-6Si-0.5Mg alloy. Maximum charge transfer resistance (R_ct) was obtained with the addition of 1 wt % Cu and minimum R_ct value was for Cu free Al-6Si-0.5Mg alloy. Due to addition of Cu and thermal modification, the magnitude of open circuit potential (OCP), corrosion potential (E_corr) and pitting corrosion potential (E_pit) of Al-6Si-0.5Mg alloy in NaCl solution were shifted to the more noble direction.