Investigation of photocathodic corrosion protection of ZnO/ZnS thin film for AISI 304 stainless steel in 3.5 wt% NaCl solution

Photocathodic protection is an alternative cathodic protection technique to protect metals by photo-generated electrons from a coupled semiconductor film under solar light. In this report, ZnO nanorods and heterostructure ZnO/ZnS nanorod films on FTO substrates were studied for their photocathodic protection for 304 stainless steels (304 SS) in a 3.5 wt% NaCl solution. The ZnO and ZnO/ZnS nanorods were fabricated on FTO substrates by spray pyrolysis and hydrothermal processes. The photocathodic performances of the ZnO and ZnO/ZnS photoanodes coupled with 304 SS samples were examined by Open-Circuit Potential (OCP), polarization curve analysis, and electrochemical impedance spectra (EIS). The ZnO/ZnS photoanodes showed better photocathodic performance than the ZnO photoanodes with larger negative potential shifts and higher photo-generated current density under light illumination. The ZnO/ZnS heterostructure films show promising photocathodic protection for 304 SS under chloride atmosphere. However, both ZnO and ZnO/ZnS failed to provide any protection under dark conditions.