Fabrication of adhesive superhydrophobic Ni-Cu-P alloy coatings with high mechanical strength by one step electrodeposition

High mechanical strength superhydrophobic Ni-Cu-P alloy coatings with strong adhesion force were one-step galvanostatically electrodeposited onto low alloy steel substrates, from a citrate- and sulphate-based bath. Surface morphologies of as-deposited Ni-Cu-P coatings were investigated by Scanning Electron Microscope (SEM). The chemical composition, structure, mechanical properties and adhesive/hydrophobic properties of coatings were characterized by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), nano-indenter, and contact angle meter, respectively. Results showed that Ni-Cu-P coatings had cauliflower-like micro-nano structures and exhibited stable hydrophobicity under different pH values and high adhesive properties without any chemical modification. Hardness test results showed that hydrophobic Ni-Cu-P alloy coatings exhibited a high hardness of about 8.5 GPa. The deposition process of coatings was proposed to illustrate the formation of cauliflower-like micro-nano structures. The mechanism of the hydrophobic and high adhesion characteristic of this surface was explained by Cassie impregnating model. This method of fabricating hydrophobic surface has potential in practical applications such as micro-droplet transportation, corrosion protection and nano patterning.