Passivity degradation and photocorrosion of X52 carbon steel under visible light illumination in concentrated carbonate/bicarbonate solutions

Corrosion of an X52 carbon steel under visible light illumination was investigated in a concentrated carbonate/bicarbonate solution. The steel is passivated in the solution without and with light illumination. The passive films are photosensitive and show the property of an n-type semiconductor. The most important finding is that the light illumination degrades the steel passivity, but the occurrence of pitting corrosion in the presence of chloride ions can be mitigated by the illumination. This is possible only under the condition that the corrosion potential of the steel is more positive than the flat-band potential of the passive film.