Superhydrophobic composite coating for reliable corrosion protection of Mg alloy

Abstract

Endowing Mg alloy surface with superhydrophobicity solves its poor corrosion resistance for broadening the wide application fields. However, the superhydrophobicity is vulnerable to failure under service environments due to the exfoliation and degradation of surface material. Hence, a bilayer composite coating composed of microarc oxidation layer and superhydrophobic layer was fabricated to protect Mg alloys by modulating superhydrophobic coating/substrate interface. The bilayer coating with a water contact angle of 158.3° possesses excellent water-repellent, and self-cleaning properties. In addition, the bilayer coating consistently remains superhydrophobicity in acid, alkaline, high/low temperature, and ultraviolet radiation environments, indicating the excellent environmental stability. Notedly, the lowest-frequency impedance value of bilayer coating (6.78 × 106 Ω·cm) increases five orders of magnitude compared with that of Mg alloy (60.2 Ω·cm), and the inhibition efficiency is calculated to be 99.99 %. The excellent corrosion resistance of coating is attributed to the synergistic barrier protection of microarc oxidation layer and superhydrophobic layer, implying that it provides effective protection for Mg alloy. Therefore, the as-prepared bilayer coating has great application prospects in corrosion protection of Mg alloys toward different service environments.

Keywords

• Magnesium alloys
• Superhydrophobic coating
• Microarc oxidation
• Synergistic protection
• Anticorrosion