Understanding of the Mechanism of Intergranular Stress Corrosion Cracking for Supermartensitic Stainless Steel from Electrochemical Point of View

Electrochemical behaviour of supermartensitic stainless steel was discussed in order to understand the mechanism of intergranular stress corrosion cracking (IGSCC).  Electrochemical potentiokinetic reactivation (EPR) tests were carried out using supermartensitic stainless steels containing Mo and no Mo in various compositions of electrolytes.  The solution specified in ASTM G108 is too corrosive for the supermartensitic stainless steel to detect its intergranular corrosion.  A rise in current density that suggested intergranular corrosion was observed in the EPR test under the weaker electrolyte with an appropriate composition in a potential range of 0 to –200 mV vs SCE.  The results of EPR tests also showed the effect of post weld heat treatment to diminish susceptibility to IGSCC.  Electrochemical noise measurement was also discussed for a detection of intergranular corrosion.