Improvement in electrochemical corrosion resistance of Mg–Al–Zn alloy by 250 keV carbon ions irradiation

Abstract

Mg–Al–Zn alloy (AZ91D) was irradiated with carbon ions at different doses (1 × 1013, 5 × 1013, 1 × 1014, 5 × 1014 and 1 × 1015 ions cm−2) by using Pelletron Accelerator. Ion energy was kept constant at 250 keV for all the irradiated samples. The range of carbon ions inside the alloy was found to be 0.67 μm. X-ray diffraction results indicated that the carbon ions irradiation of Mg alloy increases the intensity of Mg (002) plane. The average crystallite size of Mg alloy was decreased at 1 × 1013 ions cm−2 whereas an increase in the crystallite size was observed by further increasing the ion dose. The FTIR data indicated C–H, C–O, C=O and C-C vibrational modes in the irradiated samples. The electrochemical corrosion of Mg–Al–Zn alloy was investigated through potentiondynamic polarization tests in 0.9% NaCl solution. The open circuit potential (OCP) did not change at lower ion doses (up to 1 × 1014 ions cm−2), however, the OCP became more positive as the ion dose was increased to 1 × 1015 ions cm−2. Similarly, corrosion current density and corrosion rate were significantly decreased after carbon irradiation at 1 × 1015 ions cm−2. The SEM results revealed severe surface pitting of the unirradiated alloy that was reduced after the carbon ions irradiation.