Corrosion behavior of electrodeposited amorphous Ni–P coating by laser-induced crystal modifier

Amorphous Ni–P coating generates great internal stress in the process of electrodeposition due to hydrogen evolution and internal chaotic structure, thus forming surface micro-cracks and decreasing the corrosion resistance. In this study, the amorphous Ni–P coating with three-dimensional (3D) morphology was electrodeposited using a solution containing the crystal modifier induced by laser irradiation. The results show that with increasing temperature and electrochemical deposition (ECD) time, the impact of the crystal modifier on the surface morphology became more significant. The roughness (Rz) value of the coating prepared by ECD (ECDed, 10 min) was 0.76 μm, whereas that of the coating prepared by laser-assisted ECD (LECD) (LECDed, 20 μJ, 10 min) was 2.97 μm. Meanwhile, the coating immediately exhibited hydrophobic properties, and the contact angle (CA, water) reached 112° ± 2°. After electrochemical corrosion, the surface was still hydrophobic, and the CA was 113° ± 2° when the laser single pulse energy was 20 μJ. The results of Tafel analysis and electrochemical impedance spectroscopy indicated that hydrophobic surfaces with a 3D microstructure have better corrosion resistance. This is because that the 3D surface morphology replaces the cracks to improve corrosion mode. Graphical abstract