Abstract
Many methods have been reported on improving the photogenerated cathodic protection of nano-TiO2 coatings for metals. In this work, nano-TiO2 coatings doped with cerium nitrate have been developed by sol–gel method for corrosion protection of 316 L stainless steel. Surface morphology, structure, and properties of the prepared coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The corrosion protection performance of the prepared coatings was evaluated in 3 wt% NaCl solution by using electrochemical techniques in the presence and absence of simulated sunlight illumination. The results indicated that the 1.2% Ce-TiO2 coating with three layers exhibited an excellent photogenerated cathodic protection under illumination attributed to the higher separation efficiency of electron–hole pairs and higher photoelectric conversion efficiency. The results also showed that after doping with an appropriate concentration of cerium nitrate, the anti-corrosion performance of the TiO2 coating was improved even without irradiation due to the self-healing property of cerium ions.
Highlights
The applications of TiO2 coatings for photocathodic protection of steels under ultraviolet (UV) illumination have attracted considerable interest because of their unique optical and electrical properties [1,2,3,4,5,6,7]
The principle of photocathodic protection lies in the fact that when a metal coated with a thin TiO2 coating is exposed to UV irradiation, electron–hole pairs are generated in the TiO2 coating [8]
The metal substrate is maintained under a photogenerated cathode protection condition, which is caused by the sudden creation of photogenerated electron–hole pairs in the cerium ion-doped TiO2 coating
Summary
The applications of TiO2 coatings for photocathodic protection of steels under ultraviolet (UV) illumination have attracted considerable interest because of their unique optical and electrical properties [1,2,3,4,5,6,7]. The photogenerated electrons transfer to the metal substrate thereby making its electrode potential more negative than its corrosion potential. In this photoelectrochemical anticorrosion system, the TiO2 coating functions as a nonsacrificial anode when used for cathode protection of steel. The pure TiO2 coating cannot provide photogenerated cathodic protection in dark condition.
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