Wettability Variation of Different Nickel Surface Morphologies Prepared by Electrodeposition and UV Illumination

Nickel coatings were fabricated onto the copper substrate by electrodeposition and UV illumination, to obtain long-term stability of the hydrophilic surface. The effect of different fabrication strategies on the surface morphologies was discussed, to reveal the relationship between wettability variation and surface characteristics. The scanning electron microscope, energy-dispersive x-ray spectroscopy, 3D digital microscope and optical contact angle measuring system were adopted to characterize the features of coating surfaces. The results show that the surface morphology, roughness and energy have a significant influence on the variation of surface wettability. The as-prepared coatings were hydrophilic and exhibited high surface free energy. Meanwhile, UV illumination on the virgin coatings led to a slight increase in surface roughness. When exposed to air, the surface with a hemispherical agglomerate structure was more likely to be oxidized and adsorbed airborne organic hydrocarbons, resulting in a significant decrease in surface energy, especially the Lewis acid–base interactions. However, rough surfaces with large pyramid-shaped architecture maintained higher surface energy. After high-temperature aging, the content of carbon elements on the coating surfaces decreased and exhibited better metal lyophilicity. This phenomenon is attributed to organic hydrocarbon particles adsorbed on the surface reacting with the air in a high-temperature environment and then detached from the surface microstructure. This paper provides a method to optimize the surface morphology of nickel coatings on the casting roll, which make the molten metal in a good metal lyophilicity, thus improving the production efficiency of the strip and reducing the production cost.