Electrochemical Evaluation of Crevice Corrosion in Stainless Steels

摘要

An electrochemical method for the evaluation of crevice corrosion in stainless steels is described. Specimens are carefully abraded in order to give a large number of microcrevices when the specimen is placed in contact with a rubber o-ring. Twelve specimens are tested simultaneously in a purpose-built electrochemical cell. A constant potential is applied to the specimens and the temperature automatically raised at intervals until a current increase indicates the onset of crevice corrosion and thereby defines the critical crevice corrosion temperature (CCT).Testing has been performed on a wide range of stainless steels in 3.5% NaCl at +700mV SCE. The temperature was raised by 5°C every 70 minutes. Results show good reproducibility with a typical standard deviation of below 5°C. There is also excellent agreement with the ranking of crevice corrosion resistance for different steel grades which is obtained by immersion testing in 6% FeCl_3 solution.