The Photogenerated Cathodic Protection of Steel Using the Thin Layers of Photoactive Nanocomposite Fabricated By Electrophoretic Deposition

The photogenerated cathodic protection of steel can be achieved by a photoactive coating layer. It is recently attracting attention because it can overcome the limitations of the sacrificial cathodic protection method. In theory, it can provide permanent cathodic protection because it used energy from solar light rather than to consume itself to protect against corrosion of steel. In the present work, a novel nano-structured layer for the photogenerated cathodic protection was coated on steel using electrophoretic deposition (EPD). Through EPD, thin photoactive composite films can effectively be fabricated on conductive substrates using the colloidal suspension of functional nanoparticles with the simple application of an electrical field. Firstly, crystalline TiO₂ nanoparticles were deposited on a steel substrate by the EPD process for the photo-generated cathodic protection. To improve the cathodic protection ability of the photo-stimulated layer, graphene nanoplatelets were incorporated into the TiO₂ composite layer by the simultaneous co-deposition of graphene and TiO₂ nanoparticles using EPD. Despite the superior cathodic protection afforded by a photo-stimulated TiO₂ EPD layer, the coating only works when exposed to solar irradiation during the daytime. However, steel suffers from corrosion at all times. There have been many attempts to overcome this drawback. The incorporation of various photo-electron storing materials into the coating layer is the most promising strategy for maintaining the efficacy of the cathodic protection that is provided by TiO₂ in the absence of sunlight. WO₃ nanoparticles were used in this study to impart photo-generated cathodic protection to the EPD layer at all times. Moreover, the graphene was exploited as a barrier to protect steel from corrosion because it forms a better barrier to molecules. A graphene film was prepared on steel using EPD with a suspension of graphene oxide in water. When graphene was used as an underlying film for the organic coating, the corrosion resistance of the coated steel improved significantly.