Abstract
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 initiation potentials of pitting and crevice corrosion have been clearly defined and the experimental method of determination been well standardized, neither definition nor standard method has been established for stress-corrosion cracking. In this paper, the critical initiation conditions have been discussed for the kind of stress-corrosion crack that originates from corrosion crevice with intergranular stress-corrosion cracking occurring in the sensitized Type 304 stainless steel/neutral chloride solution environment system as an example. Following conclusions have been drawn: (1) The Stress-corrosion repassivation potential, 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 ER,CREV, the corrosion-crevice repassivation potential determined 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 initiation potential for stress corrosion cracking, VC,SCC, determined in the potentiostatic holding test.
