Fabrication Of TiO₂ Composite Films And Research On Its Antibacterial And Anti-corrosion Properties In Seawater

With the development of science and technology, the exploitation of marine is becoming urgent for the forecast of energy crisis in the world. The marine materials are needed in almost all the area of exploitation of marine, such as transport in ocean and marine engineering. However, marine is a very hard corrosive environment to the materials. Corrosion of marine materials, especially the corrosion caused by marine microbe could result in huge economic losses. Therefore, research on the fabrication of marine functional materials with antibacterial and anti-corrosion properties is of great importance for the exploitation of marine.In this paper, marine functional materials with antibacterial and anti-corrosion properties were fabricated to relieve the serious corrosion condition caused by attachment of marine microbe on stainless steel. The antibacterial and anti-corrosion properties of the as-obtained materials were tested by investigating the relationship between the attachment of marine microbe and the electrochemical properties.In present work, sulphate-reducing bacterium(SRB) from Qingdao offshore was obtained by isolation and purification method, for SRB was a main bacterium which caused the corrosion of metals. The growth pattern of SRB was confirmed by analyzing its growth curve, and the properties of as-obtained materials were studied in environment in which SRB existed.TiO2 film and TiO2 composite films were prepared on 304 stainless steel, in which silver ion and cerium ion were doped for their antibacterial activity. The process parameters of fabrication were discussed, on the basis of which, the optimum fabrication technology was obtained. The spectral response of TiO2 films was researched by analyzing the UV-VIS transmittance spectra. A noticeable shift of absorption edge to the visible light region was observed for TiO2 composite films, and an enhanced absorption peak appeared in the visible region, which was propitious to the photocatalytic effect of TiO2 under visible light.TiO2 film and TiO2 composite films exhibited an additional cathodic protective function to 304 stainless steel exposed to SRB in seawater by investigating their photoelectrochemical properties. Bactericidal ratio confirmed that the TiO2 films appeared strong bactericidal activity and most of SRB could be killed in seawater. Moreover, the TiO2 films could exhibit stronger bactericidal activity for the silver ion and cerium ion dopant.The antibacterial and anti-corrosion properties were investigated by means of scanning electron microscopy(SEM) and electrochemical method, comparing bare 304 stainless steel with the ones coated with TiO2 films immersed in SRB medium for different time. The results of SEM suggested that TiO2 films could prevent the attachment of SRB on substrates and decrease the extent of corrosion for 304 stainless steel immersed in SRB medium. The measurements of potentiodynamic polarization suggested that TiO2 films decreased the corrosion currents densities(Icorr), corrosion rates, which implied the inhibition of corrosion for 304 stainless steel. Furthermore, the results of electrochemical impedance spectra(EIS) showed that the impedance value decreased with immersion time, but the impedance value of TiO2 films were higher than that of bare 304 stainless steel. Utilizing the equivalent circuit models to interpret the EIS data, it could be obtained that the existence of TiO2 films increased the charge transfer resistance, and inhibited the corrosion rate of 304 stainless steel exposed to SRB in seawater.