A Comparative Study of Intergranular Corrosion of AISI 304 Stainless Steel and Chrome-Manganese Austenitic Stainless Steel

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The use of Chrome-Manganese austenitic stainless steel (Cr–Mn ASS) has tremendously increased in past few years in applications like home accessories, office appliances, light poles, etc and it is serving as an alternative to 300 series. But, the study related to sensitization behavior of these steels is scanty. Therefore, this paper aims a systematic comparison on intergranular corrosion of AISI 304 stainless steel and Cr–Mn ASS. The qualitative and quantitative comparison of degree of sensitization of these steels was carried out on the basis of optical microscopy (ASTM standard A-262 practice A test) and electrochemical test (double loop electrochemical potentiokinetic reactivation (DLEPR)) respectively. The isothermal time-temperature-sensitization diagrams were used to compare the effect of heat treatment on sensitization zone of both the steels. The DLEPR results showed that the AISI 304 SS starts to recover from sensitization when ageing time is prolonged beyond 2880 min. (at 700°C), whereas for Cr–Mn ASS, the degree of sensitization keeps on increasing to a very high value of 60.70% (11520 min.). Chromium depleted zone was identified and compared using Electron Probe Micro-analyzer (EPMA) line scan of both the steels. The depleted region of sensitized Cr–Mn ASS is found to be much wider than that of AISI 304 SS.