Photocathodic protection properties of NiP/TiO2 bilayer coatings by a combined electroless plating and sol–gel method

A combined electroless plating and sol–gel method was developed for preparing a NiP/TiO₂ bilayer coating to achieve an especial photocathodic protection effect for A3 low carbon steel. Photocathodic protection properties of the coating were investigated by the electrochemical method. Surface morphology and structure of the coating were characterized by scanning electron microscope (SEM) and X‐ray diffraction (XRD). The results show that the open circuit potential (OCP) of the NiP/TiO₂ coating electrode shifts to ?0.42 V under UV irradiation, which is lower than the corrosion potential of A3 low carbon steel. When the light is turned off, the photocathodic protection effect cannot be maintained. In addition, the mechanism of photocathodic protection for the coating was also explored.