Effects of five additives on electrochemical corrosion behaviours of AZ91D magnesium alloy in sodium chloride solution

Additives usually affect the electrochemical corrosion behaviours of metals which are immersed in the electrolyte. In this study, five additives including thiourea (TU), thiosinamine (ATU), thiosemicarbazide (TSC), sodium benzoate (Bz) and sodium citrate (SC) were added into the electrolyte respectively to investigate the electrochemical corrosion behaviours of AZ91D magnesium alloy immersed in neutral 0.05 wt-%NaCl solution. Open circuit potential (OCP), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) measurements were employed in the electrochemical tests. The results revealed that TSC showed a good inhibiting effect, and TU as well as ATU slightly improved the corrosion resistance of AZ91D magnesium alloy in the studied solutions. A negative inhibiting effect with the addition of Bz or SC was also observed. Moreover, the electrochemical results were analysed by computational chemistry method and ultraviolet absorption spectra, and the possible inhibiting mechanism was also discussed in detail.