Dissolution behavior of duplex stainless steels in crevice corrosion growth step

Aoki, So  ; Nada, Yushi*; Sakai, Junichi*

The objective of this study is to clarify dissolution behavior of duplex stainless steels in crevice corrosion growth step. Crevice corrosion grew on the duplex stainless steels by holding potential at various values. After a certain period, dissolution behavior of the crevice corrosion was analyzed based on observation of corroded area. Change in crevice corrosion dissolution behavior with time was also investigated by means of in-situ observation. Four types of dissolution regions could be observed in the corrosion area from outside toward inside direction, i.e. tip of the corroded area toward initiation point, in a crevice; they were passive region, the preferential dissolution region of austenitic phase, both phase dissolution region, and the preferential dissolution region of ferritic phase. The crevice corrosion which maintained that four dissolution regions grew toward the edge of the crevice. This dissolution behavior was given at all the potential where crevice corrosion occurred. The result is described by the micro galvanic cell between inside and outside the crevice consists of IR drop.