Corrosion resistance and electrical conductivity of V/Ce conversion coating on magnesium alloy AZ31B

A V/Ce conversion coating was deposited in the surface of AZ31B magnesium alloy in a solution containing vanadate and cerium nitrate. The coating composition and morphology were examined. The conversion coating appears to consist of a thin and cracked coating with a scattering of spherical particles. The corrosion behavior of the substrate and conversion coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Compared with AZ31B magnesium alloy, the corrosion current density of the conversion coating is decreased by two orders of magnitude. The total impedance of the V/Ce conversion coating rise to 1.6 × 10³ Ω·cm² in contrast with 2.2 × 10² Ω·cm² of the bare AZ31B. In addition, the electrical conductivity of the coating was assessed by conductivity meter and Mott-Schottky measurement. The results reveal a high dependence of the conductivity of the coating on the semiconductor properties of the phase compositions.