Photo-generated cathodic protection performance of electrophoretically Co-deposited layers of TiO2 nanoparticles and graphene nanoplatelets on steel substrate

In this work, electrophoretic deposition (EPD) was employed to deposit TiO2 nanoparticles and graphene nanoplatelets composite films onto stainless steel in order to fabricate a photo-generated cathodic protection layer. The colloidal suspension used for the EPD was characterized by the measurement of the zeta-potential of the solution using a dispersion optical analyzer. The surface morphology of the EPD layers was investigated using scanning electron microscopy (SEM), and the relative composition of the EPD layer was estimated from the peak intensities using an X-ray diffractometer (XRD) with the distinct peak at 2θ = 26.5°. Moreover, the photo-generated cathodic protection abilities were characterized by measuring the open circuit potential (OCP) and the transient photo-generated current density response from the TiO2-graphene co-deposited samples with and without exposure to UV light. The TiO2-graphene EPD layer was found to be uniform, with no noticeable particle homo-aggregation. As a result of the OCP measurement, it was verified that the EPD layers efficiently provided photo-generated cathodic protection to the stainless steel because the potential of the photo-stimulated EPD layers was more negative than the corrosion potential of the stainless steel. When 10 wt.% graphene (vs. TiO2 nanoparticles) was used in the EPD layer, the generated photo-current increased significantly from 0.08 μA∙cm− 2 to approximately 0.15 mA∙cm− 2 due to the efficient separation of the electron-hole pairs and the increased electron conductivity of the EPD film. However, it was found that the excessive incorporation of graphene nanoplatelets can impede the photocatalytic activation of the TiO2 by reducing its light absorption intensity in the UV range.