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Deposition time effects on structure and corrosion resistance of duplex MAO/Al coatings on AZ31B Mg alloy

Xue-Jun Cui (School of Materials Science and Engineering, Sichuan University of Science and Engineering, Zigong, China)
Ying-Jun Zhang (School of Materials Science and Engineering, Sichuan University of Science and Engineering, Zigong, China)
Bao-Jie Dou (School of Materials Science and Engineering, Sichuan University of Science and Engineering, Zigong, China)
Xian-Guang Zeng (School of Materials Science and Engineering, Sichuan University of Science and Engineering, Zigong, China)
Xiu-Zhou Lin (School of Materials Science and Engineering, Sichuan University of Science and Engineering, Zigong, China)

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 5 June 2017

Abstract

Purpose

This paper aims to investigate the effects of deposition time on the structure and anti-corrosion properties of a micro-arc oxidation (MAO)/Al coating on AZ31B Mg alloy.

Design/methodology/approach

The study describes the fabrication of the coating via a combined process of MAO with multi-arc ion plating. The structure, composition and corrosion resistance of the coatings were evaluated using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and electrochemical methods.

Findings

The Al-layer is tightly deposited with a good mechanical interlock along the rough interface due to the Al diffusion. However, the Al layer reduces the anti-corrosion of MAO-coated Mg alloy because of structural defects such as droplets and cavities, which act as channels for corrosive media infiltration towards the substrate. Fortunately, the Al layer improves the substrate corrosion resistance owing to its passive behaviour, and the corrosion resistance can be enhanced with increasing deposition time. All results indicate that a buffer layer fabricated through the duplex process improves the interfacial compatibility between the hard coating and soft Mg alloys.

Originality/value

An MAO/Al duplex coating was fabricated via a combined process of MAO and physical vapour deposition. MAO/Al duplex coatings exhibit obviously passive behaviours on AZ31 Mg alloy. The structure and corrosion resistance of MAO/Al coatings were investigated.

Keywords

Acknowledgements

This work was funded by the Science and Technology Planning Project (2016JZ0032) of Sichuan Province, China, the key research project (16ZA0244 and 15ZB0205) of Sichuan Education Department, China. The authors thank Jie Yang for his assistance in the experiments.

Citation

Cui, X.-J., Zhang, Y.-J., Dou, B.-J., Zeng, X.-G. and Lin, X.-Z. (2017), "Deposition time effects on structure and corrosion resistance of duplex MAO/Al coatings on AZ31B Mg alloy", Anti-Corrosion Methods and Materials, Vol. 64 No. 4, pp. 357-364. https://doi.org/10.1108/ACMM-04-2016-1666

Publisher

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Emerald Publishing Limited

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