Change of pH of inside the crevice with time during crevice corrosion initiation and growth step of a duplex stainless steel

The objective in this study was to clarify the change of pH with time inside crevice in potentiostatic crevice corrosion test. Sensing plate to discoloration by the change of pH was made. The crevice corrosion of a duplex stainless steel in potentiostatic crevice corrosion test using a sensing plate was in situ observation. The change of pH with time inside crevice was measured by discoloration of the coating agent of the sensing plate. Crevice corrosion of duplex stainless steel occurred at the point where pH is lowered locally. And, it was found that pH of crevice corrosion tip was below the depassivation pH of both phases.