Repassivation Method for Determining the Critical Potential for Initiation of Stress-Corrosion Cracking

One point of technological importance in the use of stainless steels for natural water environments such as sea and fresh waters lies with their liability to stress-corrosion cracking.The stress-corrosion crack initiation in these environments is almost always via localized corrosion such as pitting or crevice-corrosion.Although the critical potentials for initiation of pitting and corrosion-crevice have been clearly defined and the experimental method of determination has been well standardized, neither definition nor standard method has been established for stress-corrosion cracking.In this paper, the critical conditions for initiation of the kind of stress-corrosion crack that originates from a corrosioncrevice have been discussed with intergranular stress-corrosion cracking occuring in the sensitied Type 304 stainless steel/neutral chloride solution environment system as an example.Following conclusions were drawn : (1) The repassivation potential for stress-corrosion cracks, ER, sCC, can be determined in the cyclic polarization tests using a specimen provided with an artificial crevice and applying a static load on it, (2) the ER, scc thus determined was about 100 mV lower than the repassivation potential for corrosion-crevice, ER, CREV, determind for the same specimen but with no load applied, (3) effects of applied stress, degree of sensitization, test temperature, and NaCl concentration on ER, scc were documented, and (4) the ER, scc agreed with the critical potential for initiation of stresscorrosion cracking, Vc, scc, determined in the potentiostatic holding test.