Fractal characteristics and wettability of Nano-Al2O3/Ni-Co composite coating prepared by electrodeposition

Nano-Al2O3/Ni-Co composite coatings were formed on gray cast iron surface by electrodeposition method. The composite coating has a more flat surface and compact microstructure than the pure Ni-Co coating. The fractal surface structure parameters were calculated by fractal theory and the average fractal dimension is 1.301 3. The contact angles were measured and the maximum value reaches 105°. The relationship between wettability and fractal structure was explained by Cassie–Baxter equation. The results indicate that wetting behavior varies with the fractal dimension. But the change of contact angels is not directly proportional to the fractal dimension.