Effect of Process Parameters on the Corrosion Resistance Properties of PEO Coatings Produced on AZ31B Magnesium Alloy

摘要

Plasma electrolytic oxidation (PEO) can reduce the corrosion susceptibility of Mg alloys by producing a protective oxide layer. The present investigation examined the influence of PEO processing parameters on the corrosion resistance of the resulting coatings. Changes in the oxidation time, applied current density, and electrolyte temperature were shown to alter the thickness of the coating as well as its phase composition. Increasing the coating time was found to increase the thickness and uniformity of the coating. Application of a greater current density was found to increase the thickness of the outer layer, resulting in a more porous structure with reduced corrosion resistance. Elevating the temperature of the electrolyte resulted in partial dissolution of the coating, producing a thinner coating than that produced in an electrolyte at a lower temperature. The resistance to corrosion initiation was considered to be related to through-film pores in the coating, via electrochemical impedance modelling.