Comprehensive investigation of corrosion resistance of magnesium–titanium, aluminum, and aluminum–vanadium alloys in dilute electrolytes under zero-applied potential conditions

Abstract MgTi alloy exhibited the highest corrosion values (0.242–6.081 mm/year) in H 2 SO 4 compared to values obtained for Al4032, Al4004, and AlV alloys which varied from 0.270 to 1.795, 0.233 to 2.002, and −0.125 to 3.779 mm/year. The plot configuration of MgTi and other alloys showed a decrease in corrosion values with respect to exposure time. Corrosion of MgTi, Al4032, Al4004, and AlV in NaCl were significantly lower compared to H 2 SO 4 . The highest corrosion rate occurred at 0.5% NaCl and the lowest at 4.5% NaCl. MgTi alloy exhibited the highest corrosion rate with the optimal value from 0.180 to 0.794 mm/year compared to Al4032 (−0.141 and −0.458 mm/year). The corrosion rate of the alloys in acid–chloride is visibly higher compared to NaCl but significantly lower than H 2 SO 4 . MgTi exhibits the most electronegative open circuit potentials (OCPs) in acid, NaCl, and acid–chloride solution with final potential values of −1.591 and −0.233 V from 0.00625 M H 2 SO 4 and 0.1 M H 2 SO 4 , −1.631 and −1.542 V from 0.5 and 4.5% NaCl, and −1.598 and −1.576 V from acid–chloride solution. Al4032 displayed the most electropositive OCPs at −0.464 and 2.418 V from H 2 SO 4 and 2.710 and −0.650 V from NaCl solution. Optical microscopy shows MgTi and Al4004 depicting morphological degradation over its surface. Al4032 shows extensive localized deterioration while AlV depicts flake-like deterioration. Extensive morphological deterioration is visible on MgTi, Al4032, Al4004, and AlV alloys from the acid, chloride, and acid–chloride solution. The degree and type of deterioration vary with the electrolyte, electrolyte concentration, and metallurgical properties of the alloys.