Photocathodic Protection of TiO2 Composite Material on 304 Stainless Steel

TiO₂ and other semiconductor materials were found to have photocathodic protection effect for the metal coupled with these semiconductors film, as the potential of the metal shifted to a more negative value than its corrosion potential and the corrosion of the metal was prevented. TiO₂ has been one of the most important semiconductors because of its good environmental friendliness and chemical stability. However, due to the wide band gap of TiO₂ (3.2 eV) and the recombination of the photogenerated electron-hole (e^–-h⁺) pairs, it can only absorb the light with the wavelength less than 380 nm, and it is hard to maintain the cathodic protection in the dark. In this paper, CdSe and other materials were applied to improve the photocathodic protection property.

TiO₂ nanotubes was prepared by anodization method, and CdSe was deposited on the TiO₂ nanotube arrays by cyclic voltammetry method, and the optimum condition was selected from different cycles. The surface morphology and crystal phase of the composite was investigated by scanning electron microscopy (SEM), X ray diffraction (XRD) method.

The photocathodic protection property of the composite material for 304 stainless steel in seawater was investigated by the electrochemical method including open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and the tafel polarization curves method. The experimental results showed that open circuit potential of 304 stainless steel decreased from -190mV to -500mV when the light was turned on, and the electrode potential slowly rises to about -250mV after the light was turned off. The composite material still could maintain the protective effect on stainless steel after the light was turned off.

The work was supported by the Project of National Development and Reform Commission, the Nantong Science Project (BK2014008), and National Basic Research Program of China (2014CB643304).