Corrosion resistance of dodecanethiol-modified magnesium hydroxide coating on AZ31 magnesium alloy

A hydrophobic surface coating on AZ31 magnesium alloy was fabricated by combining hydrothermal treatment and subsequent chemical modification with 1-dodecanethiol (DT). The structure and morphology of the coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The roughness of samples was examined by atomic force microscope (AFM). The corrosion resistance of the hydrophobic coatings was investigated by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The results revealed that the hydrophobic coatings effectively improved the corrosion resistance of the AZ31 alloy. The hydrophobic surface obtained in presence of 10 mmol L⁻¹ DT showed a maximum static water contact angle of 105.5° and optimum corrosion resistance. There exists a “threshold” DT concentration for achieving hydrophobic coating on AZ31. Addition of an excess of DT decreased the water contact angle and corrosion resistance of coating. In the discussion part of this paper, a comparison was made with previous works. Finally, a corrosion mechanism of the coating was proposed and discussed.