Overall micro-arc oxidation treatment for AZ31B–6061 magnesium–aluminium dissimilar metal connecting parts

ABSTRACT

The magnesium–aluminium connecting parts are important application form for lightweight structural materials. But the conductive connect of magnesium and aluminium will cause serious galvanic corrosion problems. Therefore, the overall corrosion protective treatment is necessary. A ceramic coating was prepared via overall micro-arc oxidation to wrap the magnesium–aluminium connecting part integrally. The surface morphologies and compositions of the coatings were analysed by scanning electron microscopy and X-ray energy dispersive spectroscopy. The corrosion behaviour of the coatings was investigated with potentiodynamic polarisation tests in 3.5 wt-% NaCl solution. The growth process of ceramic coating on aluminium and magnesium surface was investigated, which showed the micro-arc oxidation reaction priority and the balanced growth process of ceramic coating under unbalanced micro-arc distribution. The results demonstrated that the overall micro-arc oxidation treatment improved the corrosion resistance and reduced the corrosion potential difference of each metal of magnesium–aluminium connecting part.

KEYWORDS:

• Micro-arc oxidation
• ceramic coating
• magnesium–aluminium dissimilar metals
• connecting part

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Jixue Zhou http://orcid.org/0000-0002-6159-0417

Hongtao Liu http://orcid.org/0000-0002-3583-8714

Additional information

Funding

This paper was supported by Chinese national key research and development plan (2016YFB0301105) and Key Technology of Science and Technology Department of Shandong Province (2016ZDJS02A09).