Protective Micro-Arc Oxidation Surface Coating on AZ80 Forged Magnesium Alloy

Abstract

Magnesium alloys, with a high weight-to-strength ratio, have attracted considerable attention for lightweight applications, especially in automotive industry. However, their inferior corrosion properties when in contact with aqueous solutions, salt, and other metals have become a significant hindrance to more widespread use of magnesium alloys. Surface coating has been considered an economic and effective strategy for corrosion protection of magnesium alloys. In this work, the corrosion behavior of uncoated and micro-arc oxidation (MAO) coated cast, extruded, and forged AZ80 magnesium alloys has been studied using salt fog corrosion chamber test and microscopic characterization techniques. The influence of the forging process and MAO surface treatment on the corrosion properties of the AZ80 magnesium alloys was investigated. The experimental results showed that the low forging temperature of 250 °C led to fine grain size and uniform distribution of secondary phase in the magnesium alloy, resulting in higher corrosion resistance. The MAO coating provided significant corrosion protection of the AZ80 magnesium alloy substrates in the aggressive continuous salt fog environment.KeywordsMagnesium alloyCorrosion protectionForgingMicro-arc oxidationSurface coating