A STUDY ON CREVICE CORROSION OF PIPELINE STEEL UNDER DISBONDED COATING HOLIDAY IN SIMULATED SOLUTION OF KU'ERLE SOIL WEST OF CHINA

摘要

Generally, crevice corrosion of steels would take place within corrosion block section between coating and steels. Disbonded coating holiday leads to heavy crevice corrosion to pipeline steels. A wedge-shaped crevice cell used to model previously disbonded coating holiday of X70 pipeline steels under impressed current cathodic protection in simulated solution of Ku'erle (west of China) soil. Potentials and current distributions along long direction of a wedge-shaped crevice were measured at different opening applied potentials (-850mV, -1000mV and -1150mV vs CSE), at various polarization time and at three kinds of crevice opening size (0.15mm, 0.30mm and 0.45mm). The influence of applied potentials and crevice size on distributions of polarization potentials, current and pH value in crevice were investigated. It was shown that the gradients of polarization potential and current in crevice gradually decreased with increase of measure time. It was found also that, with negative shift of the applied potential and increase of crevice opening size, the polarization potentials decreased, the polarization current and pH value increased for all samples in crevice.