Development of Cast AZ63 Magnesium Alloys for Cathodic Protection Applications via Alloying Additives

Abstract

Applying sacrificial anodes to safeguard structures requires better exposure resistance. The effect of adding Ca (x = 0.1, 0.4, 0.7, and 1.0 wt%) and Ti (x = 0.1, 0.2, 0.3, 0.4, and 0.5 wt%) on the microstructure and electrochemical properties of AZ63 magnesium anode alloy has been studied. The corrosion resistance was examined in 3.5 wt% NaCl utilizing electrochemical impedance spectroscopy and potentiodynamic polarization. The microstructure of the base alloy, comprised of primary α-Mg and secondary phase Mg₁₇Al₁₂, extended to grain boundaries. The corrosion resistance was amended by adding the Ti element, which is correlated to the morphology and dispersion of the TiAl₃ phase at the grain boundary. Adding Ca over 0.1 wt% increased the corrosion rate due to the formation of a highly reactive Mg₂Ca phase. It implies that AZ63 alloy anodes are viable.