Cathodic polarization characteristic of wedge-shaped crevice of X70 pipeline steel

Cathodic polarization characteristic of a wedge-shaped crevice of X70 pipeline steel was studied under impressed current cathodic protection in simulated solution of desert soil of Ku'erle in Xinjiang of China. The influences of applied control potentials (-775 mV, -925 mV) and -1075 mV (vs SCE)) and crevice thicknesses (0.15 mm, 0.30 mm and 0.45 mm) on polarization potentials, polarization current and pH value in crevice were investigated. It was shown that the gradients of polarization potential and current in crevice gradually decreased with time. Moreover, with lowering of opening control potential and growing of crevice opening thickness, the polarization potentials in crevice decreased and the polarization current and the pH value in crevice increased. More negative shift of the control potentials and bigger crevice opening thickness can make the growth rate of pH value decrease.