Preparation and Corrosion Behavior in Marine Environment of MAO Coatings on Magnesium Alloy

Yuhong Yao; Wei Yang; Dongjie Liu; Wei Gao; Jian Chen

doi:10.3390/ma13020345

Preparation and Corrosion Behavior in Marine Environment of MAO Coatings on Magnesium Alloy

Materials (Basel). 2020 Jan 12;13(2):345. doi: 10.3390/ma13020345.

Authors

Yuhong Yao¹, Wei Yang¹, Dongjie Liu², Wei Gao¹, Jian Chen¹

Affiliations

¹ School of Materials Science and Chemical Engineering, Xi'an Technological University, Xi'an 710032, China.
² School of Materials Science and Engineering, Xi'an University of Technology, Xi'an 710048, China.

Abstract

To improve the corrosion performance of magnesium alloys in the marine environment, the MAO, MAO-Cu₂CO₃(OH)₂·H₂O and MAO-Cu₂P₂O₇ ceramic coatings were deposited on AZ91D magnesium alloys in basic electrolyte and the discoloration mechanism of the Cu-doped MAO coatings and the corrosion behavior of the three MAO coatings in the artificial seawater solution were investigated by SEM, EDS and XPS. The results indicated that the formation and discoloration mechanism of the brown MAO ceramic coatings were attributable to the formation of Cu₂O in the coatings. Though the three MAO coatings had a certain protective effect against the corrosion of AZ91D substrate in the artificial seawater, the distinctive stratification phenomenon was found on the MAO-Cu₂P₂O₇ coated sample and the corrosion model of the MAO-Cu₂P₂O₇ coatings in the immersion experiment was established. Therefore, the brown Cu-doped MAO coatings were speculated to significantly reduce the risk of the magnesium parts in marine environments.

Keywords: MAO coating; corrosion behavior; magnesium alloy; marine environments; stratification phenomena.