This study investigated the photo-to-current conversion properties and photoelectrochemical cathodic protection performance of g-C3N4 in 304 stainless steel under visible or white light illumination for the first time. The results showed that the g-C3N4 thin film could provide 304 stainless steel with very good cathodic protection in the presence of light irradiation. The application of this material represents a potential breakthrough in photoelectrochemical cathodic protection technology. (C) 2012 Elsevier Ltd. All rights reserved.