Microstructural evolution and corrosion resistance of super-hydrophobic electrodeposited nickel films

Superhydrophobic coatings have become a hot research topic in recent years due to their excellent properties and wide practical applications. In the present work, hierarchical nickel films having intrinsic super-hydrophilic property were fabricated on copper substrate by two-step electrodeposition process. The surface structure and composition were characterized by means of scanning electron microscopy (SEM), X-ray diffraction pattern (XRD) and atomic force microscopy (AFM). The contact angle of water droplets on the hierarchical structure of nickel films increased over time, eventually becoming large enough to classify the surface as superhydrophobic. The surface morphology of nickel film at micro/nano scale was characterized at different deposition current densities (10-70 mA cm(-2)). Results showed that the value of roughness and the size of micro/nano cones were decreased by increasing the current density. The nickel film deposited at 20 mA cm-2 displayed the highest superhydrophobicity with water contact angle of 155 degrees, which could be attributed to its pine cone-like structure. Electrochemical measurements and long-term immersion test showed that the superhydrophobic nickel films greatly enhanced the corrosion resistance of copper substrate in neutral 3.5 wt.% NaCl solution. The corrosion protection of superhydrophobic films was attributed to small area of real contact with the aggressive solution. (C) 2015 Elsevier B.V. All rights reserved.