Korean Institute of Surface Engineering

pISSN : 1225-8024 | eISSN : 3399-8403

공학

한국표면공학회지 (50권6호 432-438)

Fabrication of Plasma Electrolytic Oxidation Coatings on Magnesium AZ91D Casting Alloys


Lee, Sung-Hyung;Yashiro, Hitoshi;Kure-Chu, Song-Zhu;


GEO Nation Co. Ltd.;Department of Chemistry and Bioengineering, Iwate University;Materials Function and Design, Nagoya Institute of Technology;

DOI : 10.5695/JKISE.2017.50.6.432

Abstract

AZ91D casting alloy requires an advanced plasma anodizing processing because large amount of defects are liable to generate during anodization. In this study, plasma electrolytic oxidation (PEO) of AZ91D Mg alloy was conducted by the application of either constant voltage or current using a pulse mode and its effects on pore formation, surface roughness and corrosion resistance were investigated. The PEO films showed a three-layer structure. The PEO film thickness was found to increase linearly with voltage. The surface roughness, Ra, ranged between $0.2{mu}m$ and $0.3{mu}m$. The corrosion resistance increased from RN 3.5 to 9.5 by the PEO treatment when evaluated according to the 72 hour salt spray test. The PEO-treated surface exhibited higher pitting potential than the raw material.

Keywords

AZ91D magnesium alloy;Unipolar pulse;Anodic oxidation;Plasma;Ceramic coatings;Corrosion resistance;Surface roughness;