Electrochemical corrosion behavior of Ni-containing hypoeutectic Al-Si alloy

Abstract

Electrochemical corrosion characteristics of the thermally treated 2 wt % Ni-containing Al-6Si-0.5Mg alloy were studied in NaCl solutions. The corrosion behavior of thermally treated (T6) Al-6Si-0.5Mg (-2Ni) alloys in 0.1 M NaCl solution was investigated by electrochemical potentiodynamic polarization technique consisting of linear polarization method using the fit of Tafel plot and electrochemical impedance spectroscopy (EIS) techniques. Generally, linear polarization experiments revealed a decrease of the corrosion rate at thermal treated Al-6Si-0.5Mg-2Ni alloy. The EIS test results showed that there is no significant change in charge transfer resistance (R_ct) after addition of Ni to Al-6Si-0.5Mg alloy. The magnitude of the positive shift in the open circuit potential (OCP), corrosion potential (E_corr) and pitting corrosion potential (E_pit) increased with the addition of Ni to Al-6Si-0.5Mg alloy. The forms of corrosion in the studied Al-6Si-0.5Mg alloy (except Al-6Si-0.5Mg-2Ni alloy) are pitting corrosion as obtained from the scanning electron microscopy (SEM) study.