The effect of heat treatment on corrosion behaviour of Ni-P-3 gr/lit Cu nano-composite coating

In this investigation, the effect of heat treatment on corrosion behaviour of Ni-P-Cu nano-composite coating was studied. Initially, an Ni-P-(3 g l(-1)) Cu nano-composite coating was produced under the bath condition of pH = 4.5-5, RPM = 400. The coatings were then heat treated at 400 degrees C for 1h. Scanning electron microscope (SEM), electron dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed to analyse the coating characteristics. As well, corrosion resistance of the coatings in a solution of 1 M HCl was explored by potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Results show that heat treatment for 1 h at 400 degrees C crystallised the Ni-P-Cu coating and changed the amorphous morphology of the coating. This crystallisation also decreased corrosion resistance mainly due to P content reduction of the nano-composite coating. Finally, heat treatment reduced the P content of the coating as it formed different phases such as Cu3P, Ni8P3, Ni5P2 and CuP2.