2011 Volume 60 Issue 8 Pages 363-367
Relationship between preferential dissolution behavior and the holding potential and its duration of the potentiostatic test of a duplex stainless steel in simulated solution inside corroding crevice was investigated. In the active region (−370, −300 and −260 mV vs. SCE), the current density decreased towards a certain value after the measurement started, then it stayed rather constant value until the end of the measurement, i.e., for 24 h. In the passive region (−200 and −150 mV), it decreased greatly towards certain values after the measurement started, then it stayed lower value until the end of the measurement. In all potential regions, current density values determined by potentiostatic tests showed about one order of magnitude lower than those of the dynamic anodic polarization curves. At the less noble potential (−370 mV) of the active region, ferritic phase preferentially dissolved, while that of noble (−260 mV) of the active region, the austenitic phase dissolved preferentially. In the passive region, both phases dissolved evenly. These dissolution behavior were observed in the potentiostatic tests for 15 min as well as for 24 h. Chemical composition of dissolved metal ions after dissolution tests at certain potentials in the active region was also analyzed. Chemical composition of dissolved metal ions was almost same as chemical composition of a preferential dissolution phase of the specimen at each holding potential. It would appear that chemical composition of dissolved metal into crevice solution reflects to the preferential dissolution phase.
