Preparation and corrosion resistance of basic carbonate coating on ZK61M magnesium alloy

In this study, a simple in-situ preparation method for coating on Mg-Zn alloy in a carbonic acid solution was investigated. The formation of a precursor carbonate layer on the alloy surface was observed. As the soaking time increased, the solution gradually turned alkaline, leading to the transformation of the precursor into a basic carbonate coating with a layered hydroxide structure. The corrosion potential (Ecorr) of the coated samples initially decreased and then increased with increasing the soaking time. After 2 h of soaking, the lowest corrosion potential observed was approximately −1.5105 V. At 12 h, the corrosion potential reached around −1.4645 V, which was comparable to that of the ZK61M magnesium alloy. After 48 h, the corrosion potential was measured to be approximately −1.3507 V.