Corrosion resistance of a superhydrophobic dodecyltrimethoxysilane coating on magnesium hydroxide-pretreated magnesium alloy AZ31 by electrodeposition

Abstract

Superhydrophobic coatings can remarkably improve the anti-corrosion performance of many materials. In this study, a fluorine-free superhydrophobic Mg(OH) 2 /DTMS composite coating was successfully fabricated on the surface of Mg alloy AZ31 by hydrothermal process and electrodeposition of dodecyltrimethoxysilane to enhance corrosion resistance. The corrosion resistance of the coating was tested using a potentiodynamic polarization scan, electrochemical impedance spectroscopy (EIS), and hydrogen evolution measurements. The superhydrophobicity was investigated by measuring water contact angles and sliding angles. The results showed that the Mg(OH) 2 /DTMS composite coating was composed of walnut-like micro/nanostructures and exhibited superhydrophobicity with a contact angle of 165.1° ± 2.1° and a sliding angle of 3.5° ± 0.6°. Moreover, the corrosion current density of the composite coating (1.777 × 10 −8 A·cm −2 ) decreased about three orders of magnitude compared with uncoated AZ31 substrate (7.342 × 10 −5 A·cm −2 ), suggesting that the composite coating had excellent corrosion resistance. Finally, the anti-corrosion mechanism of the composite coating was also addressed. To improve the anti-corrosion performance of magnesium alloys, a superhydrophobic Mg(OH) 2 /DTMS composite coating was successfully fabricated on the surface of Mg alloy AZ31. The biomimetic micro/nanostructures and low surface energy coating has been successfully obtained, which exhibit high self-cleaning performance. Moreover, the results not only provide the composite coating effectively reduce the direct contact of the AZ31 substrate with corrosive species, but also served as a physical barrier to corrosive agents. This new composite coating was anticipated to find promising applications for Mg alloys.