Inhibiting Corrosion of Mg Alloy AZ31B-H24 Sheet Metal with Lithium Carbonate

The objective of this work was to determine the effectiveness of dissolved Li₂CO₃ as a corrosion inhibitor for AZ31B-H24 sheet metal when immersed in NaCl (aq) at ambient temperature. Corrosion rates were determined by gravimetric mass loss and volumetric H₂ evolution measurements and the observed inhibition was investigated further using potentiodynamic polarization, scanning vibrating electrode technique, and x-ray photoelectron surface analytical measurements. It is shown that dissolved Li₂CO₃ significantly inhibits corrosion as it reduces the corrosion rate by a factor of 10. The manner in which inhibition is achieved is rationalized by the role played by the surface film produced during corrosion in inhibiting both the anode (anodic dissolution) and cathode (H₂ evolution) kinetics. Inhibition involves the suppression of the filament-like corrosion mode, albeit on the macroscale, and associated cathodic activation. By process of elimination, it is proposed that the Li⁺ cations play a key role in inhibiting the anodic dissolution and associated cathodic activation that is required to drive the filament-like corrosion.