Study of filiform corrosion inhibition by a compact plasma electrolytic oxidation film on a AZ31 Mg alloy

Abstract

This work reports that the filiform corrosion of a AZ31B Mg alloy can be inhibited by compact plasma electrolytic oxidation (PEO) under a transient self-feedback control mode. Corrosion protection of the C-PEO film was investigated through an immersion test of 3.5 wt% NaCl solution and a simulative service environment test of NSST, respectively. The results revealed that compactness of the film significantly influenced the corrosion protection property of the C-PEO-coated Mg alloy, and the results are summarized as follows: (1) good compactness of the PEO film prevented the soluble ions from diffusing into the scratch; (2) the high insulation of the compact PEO film can slow down cathodic current; (3) the corrosion products could deposit on the scratch and block the active sites on the Mg alloy surface.