Photocathodic protection effect of TiO2 films for carbon steel in 3% NaCl solutions

Titanium dioxide (TiO2) films were prepared by anodization of titanium foils at different voltages in dilute NaOH solutions and characterized by XRD and scanning electron microscopy (SEM) techniques. The thin TiO2 films are mainly composed of anatase phase in the form of nano-crystallites. The photoelectrochemical behavior and photocathodic protection effect for these films were also investigated in 3% NaCl solutions by using electrochemical measurement techniques and coupling test. The tremendous decrease of film resistance and open circuit potential of each TiO2 film takes place under ultraviolet (UV) illumination. TiO2 film formed at 120 V can serve as photoanode and supply a protective photocurrent about 8 μA/cm2 to carbon steel, when it is connected to carbon steel in test solution with an area ratio of 2:1. But TiO2 films can accelerate the corrosion of carbon steel in the dark. In addition, electrochemical impedance spectroscopy (EIS) characteristics and coupling behaviors for TiO2 films were discussed in detail.