Influence of UV Irradiation on Corrosion Behavior of 304L SS in 0.1M H2SO4 and 0.5M NaCl

This paper describes an experimental study on the effect of Ultra-Violet (UV) exposure on the electrochemical corrosion behavior of 304L stainless steel in 0.1M H2SO4 and 0.5M NaCl medium. The results of study demonstrate that in NaCl medium, exposure of both UV-A and UV-C shifts the Open Circuit Potential (OCP) in active direction (less noble) as compared to the specimen without UV exposure which indicates less stable passive film. While in sulphuric acid both UV-A and UV-C shifts OCP in noble direction which reflects the stability nature of passive film. In H2SO4 medium, exposure of both UV-A and UV-C assist in improving passivity which is indicated by lower passive current density. In NaCl medium, exposure of both UV-A and UV-C, decrease the pitting corrosion resistance as indicated by lower Epit (pitting potential) and higher Icorr (corrosion current density). In H2SO4 uniform dissolution was observed after each polarization experiment as shown in optical micrographs. In NaCl medium pitting sites are more under both type UV exposures as revealed by microstructure after polarization experiment. EIS (Nyquist plots) showed that exposure of both UV-A and UV-C in NaCl medium specimens have lower polarization resistance (Rp) than without UV exposure. Lower Rp confirms lesser protectiveness of passive film. In case of H2SO4, higher arc radius (Rp) is observed under UV exposure for both UV-A and UV-C.