Li2CO3 Surface Pre-Treatment for Improved Corrosion Control of Mg Alloy Sheet Metal

The objective of this work was to determine the extent to which a Li2CO3 surface-pretreatment can control corrosion of ZEK100 Mg alloy sheet metal product for automotive applications. The Li2CO3 surface treatment was applied through a dip coating processing using an alkaline Li salt aqueous solution. The structure and composition of the coating was determined using XRD and electron microscopy and associated techniques. The extent of corrosion control was determined using conventional electrochemical measurements including open-circuit potential, potentiodynamic, and electrochemical impedance spectroscopy measurements conducting in 0.1 M NaCl (aq). The performance of the surface pre-treatment was benchmarked against a commercial hexafluro-titanate/zirconate-based conversion coating. Cyclic corrosion testing was also conducted to gauge corrosion control under more realistic conditions, following a commercial OEM testing protocol. The results show that the Li2CO3 surface pre-treatment offers improve corrosion control relative to the commercial baseline coating. The manner in which the dissolution chemistry controls corrosion of the substrate will be discussed in this presentation.