Characterization of the corrosion performances of as‐cast Mg–Al and Mg–Zn magnesium alloys with microarc oxidation coatings

Abstract

In the present study, corrosion-protective microarc oxidation (MAO) coatings were prepared on AZ31B, AZ80, and ZK60 cast magnesium alloy substrates in an alkaline silicate electrolyte. The corrosion performances of the uncoated and MAO-coated alloys were investigated using electrochemical and salt spray chamber corrosion tests. The microstructure characterization and experimental results show that among the three alloys studied, the ZK60 Mg alloy exhibited the best and AZ31B the least corrosion resistance under the salt spray conditions. The MAO coating provided robust corrosion protection of the Mg substrates and resulted in a significant decrease in the corrosion rate of the alloys by 3-4 orders of magnitude. The MAO coating on ZK60 alloy showed better corrosion protectiveness than that on the AZ series alloys due to the incorporation of different alloying elements in the coating, especially the Zn and Al elements, which are from the Mg substrate. The corrosion performances and mechanisms of the uncoated and MAO-coated Mg alloys are interpreted in terms of the microstructure and phase/chemical compositions of both the substrates and coatings. K E Y W O R D S electrochemical testing, magnesium alloys, microarc oxidation, salt spray corrosion test

Influence of Al Content on Degradation Behavior of Cu-Doped Mg-Al Alloys for Drill-Free Plugging Applications

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Fabrication and properties of the superhydrophobic ceria‐based composite coating on magnesium alloy

“…[3,4] The application of high-quality surface barrier layers can effectively improve the corrosion resistance of magnesium alloys, such as protective layers obtained by chemical conversion treatment, micro-arc oxidation treatment, electroplating, and electroless plating. [5][6][7] Chemical conversion treatment has been widely developed due to the concise preparation process. Rare earth conversion coatings are some of the most promising substitutes for traditional chromate conversion coatings, which is a toxic compound and has been prohibited from being used at present.…”

Ultrasonic Treatment Induced Fluoride Conversion Coating without Pores for High Corrosion Resistance of Mg Alloy

“…To protect Mg alloy against corrosion and to maintain their mechanical integrity, various kinds of anti-corrosion techniques have been developed, such as phosphating treatment, microarc oxidation and polymer coating [8][9][10][11][12]. Although these surface modifications are ways of preventing corrosion and maintaining the mechanical strength of Mg alloy to some extent [13], there are a lack of chemical bonding interfaces between Mg alloy substrate and the protective coating.…”