Silica nanoparticles enhanced polysiloxane-modified nickel-based coatings on Mg alloy for robust superhydrophobicity and high corrosion resistance

A stable composite coating with good superhydrophobicity and corrosion resistance was fabricated on the magnesium alloy surface. The composite coating consists of a rough nickel structure prepared by chemical deposition of nickel‑phosphorus alloy and electrodeposition of nano-cone-shaped pure nickel film sequentially, and a nanoparticles-doped superhydrophobic polysiloxane film. The successful construction of the composite coating was ascertained by characterizing the chemical structure , elements, bonding information, and surface morphology using X-ray diffractometer (XRD), X-ray electron spectroscopy (XPS), and scanning electron microscopy (SEM), etc. The wear resistance and wettability tests show that the pristine composite coatings modified with either SiO 2 (ELNi/ECNi/Ms) or ZnO (ELNi/ECNi/Mz) nanoparticles had good superhydrophobicity. However, the ELNi/ECNi/Ms. coating was more stable than the latter in wettability after abrasion. The ELNi/ECNi/Ms. composite coating with the addition of 2.0 wt% SiO 2 nanoparticle formed an optimal superhydrophobic surface showing the highest water contact angle (165.3° ± 1.5°) and the lowest water sliding angle (2.2° ± 0.7°). Electrochemical tests indicate that, in contrast to naked magnesium alloy , the low-frequency impedance modulus (| Z | ƒ =0.01 Hz ) and the corrosion current density of the ELNi/ECNi/Ms. composite coatings were respectively increased and decreased by nearly four orders of magnitude, demonstrating the excellent corrosion protection .