O-PHTHALIC ANHYDRIDE AS AN EXCELLENT VAPOR PHASE CORROSION INHIBITOR FOR Mg ALLOY AZ31B UNDER SIMULATED OCEAN-ATMOSPHERE ENVIRONMENT

Magnesium alloy with good application potential has a poor corrosion resistance, so it is essential to develop a new corrosion inhibitor and investigate the inhibition mechanism for magnesium alloy. In this work, three vapor phase corrosion inhibitors (VCIs) were used for AZ31B magnesium alloy under a simulated ocean–atmosphere environment, and the inhibition behaviors and mechanisms were studied. The inhibition performances of the three VCIs were evaluated by Digital Still Camera, electrochemical tests and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) combined with X-ray photoelectron spectroscopy (XPS) was used to further explore the inhibition mechanism. Compared to benzoic acid and ammonium benzoate, o-phthalic anhydride can provide the best protection for AZ31B magnesium alloy. The icorr was reduced from 11.18 μA cm−2 (blank) to 0.65 μA cm−2 and the (Rf + Rct) was increased from 1478.1 Ω cm2 (blank) to 3129.8 Ω cm2 with o-phthalic anhydride as VCI. O-phthalic anhydride combined with Mg2+ to form different complexes with different molecular weights, which developed a more compact protective film on the AZ31B surface. Overall, the o-phthalic anhydride can be utilized as an excellent VCI for AZ31B magnesium alloy in a simulated ocean–atmosphere environment.