Raman spectroscopy study on intergranular corrosion sensitivity of 304 austenitic stainless steel

• Characteristic Raman peak of intergranular corrosion is 1492 cm −1 . • The sensitized weld revealed higher degree of intergranular corrosion. • The higher the degree of corrosion, the stronger the characteristic peak intensity. • Raman mapping provides a quantitative method for intergranular corrosion detection. Composition and intergranular corrosion characteristics of 304 austenitic stainless steel before and after sensitization were studied by inductively coupled plasma (ICP), X-ray diffraction (XRD) and Raman spectroscopy. Chromium content in the matrix and weld components revealed an evidenced decrease by 39.41 % and 95.26 % respectively after sensitization treatment. The characteristic peak at 1492 cm −1 by Raman spectroscopy was related to the Fe 2+ presence with consideration of the intergranular corrosion (Fe-2e→Fe 2+ ). In comparison, the weld part after sensitization treatment revealed a higher intensity of such characteristic peak than the unsensitized part. In addition, Raman mapping results at 1492 cm −1 revealed that the most severe corrosion occurred in the areas with higher precipitate concentrations within the sensitized weld region.