Formation of Superhydrophobic Composite Electrochemical Coatings Zn-Al2O3

In this study, superhydrophobic coatings based on a zinc composite with micro- and nanosized aluminum oxide particles were obtained. Electrodeposition of the composite was used to achieve the required polymodal roughness of the metal surface, and stearic acid was used as a surface energy-reducing agent. Metal crystallite microstructures were formed during zinc deposition. To obtain submicrostructures in the coating, Al2O3 nanoparticles with a size of ~40 nm were introduced into the electrolyte. However, to achieve a sufficient density of nanostructures on the surface, the concentration of Al2O3 nanoparticles should be greater than 10 g/L, which inevitably led to the formation of large agglomerates (>1000 nm) even with intensive stirring. To break up the agglomerates, larger Al2O3 particles with a size of ~10 μm and at a higher concentration were used. It was assumed that, having a greater mass than loose agglomerates, microparticles would act as grinding bodies, colliding with agglomerates during mixing and breaking the latter into smaller agglomerates (<250 nm) and individual particles. Composite coatings Zn-Al2O3 demonstrated high anticorrosion properties; they retained superhydrophobic properties (θc > 150°) for at least 100 h in the corrosive conditions of neutral salt mist. To evaluate the mechanical properties of the obtained superhydrophobic Zn-Al2O3 coatings, they were put to a water jet test and remained superhydrophobic for 10 min of testing.