Fabrication and properties of a superhydrophobic film on an electroless plated magnesium alloy

Abstract

A superhydrophobic coating is an outstanding barrier layer isolating the substrate from the corrosive medium, thus enhancing corrosion resistance. In this paper, a superhydrophobic film on the electroless Ni–P plated AZ61 magnesium alloy was fabricated via hydrothermal method and subsequently immersed in stearic acid solution to improve its anti-corrosion properties and self-cleaning performance. The surface morphology, structure, chemical composition and properties were investigated using scanning electron microscope (SEM), X-ray diffractometer (XRD), Fourier-transform infrared spectrophotometer (FTIR), micro-Raman spectrometer, optical contact angle meter and electrochemical workstation. The results showed that the plated Ni–P surface was hydrophilic, but it turned superhydrophobic after modification by hydrothermal reaction and stearic acid. We found the temperature and time of hydrothermal reaction could influence the morphology and wettability of the superhydrophobic nature deeply, and the petal-shaped nanosheets resulting at higher temperature had a higher hydrophobicity than the lemongrass-like nanostructures at the lower temperature. The maximum contact angle of 155.6 ± 0.3° and a sliding angle about 2° were obtained under conditions of reaction temperature of 120 °C and reaction time of 15 h. Meanwhile, the chemical stability, mechanical durability and self-cleaning performance of the formed superhydrophobic film were examined. And the potentiodynamic polarization and electrochemical impedance spectroscopy results indicated the corrosion resistance of the AZ61 substrate was improved a lot in 3.5% NaCl.