Fluoride-dominated coating on Mg alloys fabricated by plasma electrolytic process in ambient non-aqueous electrolyte

ABSTRACT

In this work, the non-aqueous NH₄F-EG electrolyte was utilized for plasma electrolytic oxidation (PEO) process on AZ91 alloy to fabricate MgF₂-dominated coating at room temperature. Results revealed that the coating had a homogeneous composition and porous microstructure. Compared with the bare AZ91 samples, the coated samples showed a 109 mV nobler corrosion potential and two orders of magnitude lower corrosion current in neutral 3.5 wt% NaCl solution, while a 54 mV nobler corrosion potential and one orders of magnitude lower corrosion current in acidic 3.5 wt% NaCl solution (pH=3). Thus, it’s unveiled a novel possibility to prepare non-oxide coating on Mg alloy by PEO process in non-aqueous electrolyte. And the MgF₂ coating provided effective corrosion protection for Mg alloy both in neutral and acid corrosive media.

KEYWORDS:

• Plasma electrolytic oxidation
• non-aqueous electrolyte
• MgF₂ coating
• magnesium alloy
• plasma electrolytic fluorination

Acknowledgments

This work was supported by One-Three-Five Strategic Planning of Chinese Academy of Sciences (CAS). The authors are grateful to Mr Guantao Kou and Dr Dongmei Li for the SEM and XRD characterization, respectively.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by One-Three-Five Strategic Planning of Chinese Academy of Sciences (CAS).