Antibacterial Properties and Corrosion Resistance of Nitrogen-doped TiO2 Coatings on Stainless Steel

The Nitrogen-doped TiO2 (N-TiO2) coatings were fabricated on 304 austenitic stainless steel (SS) substrates by oxidation of titanium nitride coatings, which were prepared by plasma surface alloying technique. Microstructural investigation, corrosion tests and antibacterial tests were conducted to study the properties of N-TiO2 coatings. Composition analysis shows that the SS substrates were shielded by the N-TiO2 coatings entirely. The N-TiO2 coatings are anatase in structure as characterized by X-ray diffraction. The corrosion properties of N-TiO2 coated SS samples in Hanks' solution were investigated by a series of tests. The electrochemical measurements indicate that the corrosion potential positively shifts from −0.275 V for untrated SS to −0.267 V for N-TiO2, while the corrosion current density decreases from 1.3×10−5 A/cm2 to 4.1×10−6A/cm2. The corrosion resistance obtained by fitting the impedance spectra also reveals that the N-TiO2 coatings provide good protection for SS substrate against corrosion in Hanks' solution. Electrochemistry noise tests indicate that the N-TiO2 coatings effectively retard the local pitting and crevice corrosion of the SS substrate. The results of the antibacterial test reveal that N-TiO2 coatings give 304 austenitic SS an excellent antibacterial property.