X70管线钢楔型缝隙的阴极极化特性

CATHODIC POLARIZATION CHARACTERISTIC OF WEDGE-SHAPED CREVICE OF X70 PIPELINE STEEL

应用楔型缝隙模型研究了X70管线钢在新疆库尔勒土壤模拟溶液中的阴极极化特性．研究了极化时间(1-30 h)、缝口控电位(-775,-925和-1075 mV(vs SCE))和缝口尺寸(0．15,0．30和0．45 mm)等因素对缝内的极化电位、极化电流以及对应介质pH值的影响．结果表明,随着极化时间的延长,从缝口到缝底的极化电位梯度和极化电流梯度逐渐减小;随着缝口控电位的降低和缝口尺寸的增大,缝内试样的极化电位逐渐降低,而极化电流却逐渐增大,缝内试样对应介质的pH值也逐渐提高,进一步降低缝口控电位与增加缝口尺寸将使pH值的增加速度减小．

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.