Enhancement in intergranular corrosion resistance of the stabilised ultra-pure 430LX ferritic stainless steel by tin addition

The intergranular corrosion (IGC) susceptibility of the Ti-Nb-stabilised ultra-pure 430LX FSSs with 0-0.47 wt-% tin addition was investigated using double loop electrochemical potentiokinetic reactivation (DL-EPR) and oxalic acid etch tests. The result of DL-EPR test reveals that IGC resistance increases with the increase in tin content. The specimens with different contents of tin exhibit the same microstructural evolution based on oxalic acid etch test. M23C6 precipitates form along grain boundaries, inducing Cr-depleted zones and finally resulting in the susceptibility to IGC. Tin addition gives rise to the formation of SnO2 on the FSSs surface, thus inhibiting the attack of corrosive ions towards Cr-depleted zones.