交流干扰对阴极保护下X80管线钢腐蚀行为的影响

Electrochemical Impedance Spectroscopy Studies on the AC Interference on Corrosion of X80 Steel

采用电化学阻抗谱法(EIS)研究了交流电对阴极保护下X80钢腐蚀行为的影响,EIS结果表明,EIS曲线包含两个时间常数,即高频电容弧和低频电感,通过等效电路LR(RQ)拟合表明,容抗弧随着交流电压的增加而减小,其电荷传递电阻(Rc)值从无交流干扰时的1669Ω.cm2减小到9V交流干扰时的566Ω.cm2,从而使腐蚀速率加快,降低阴极保护的保护程度。研究还表明,提高阴极保护电压的方法,将无法有效抑制交流干扰。

Alternating current(AC) induced-corrosion of X80 steel under cathodic protection protection(CP) condition was studied by electrochemical impedance spectra(EIS).Experiments show that: EIS curves contain two time constants which represent high-frequency capacitance arc and low-frequency inductive loop,respectively.The equivalent circuit LR(RQ) fitting data show that the AC interference can cause the interface electric double layer between the X80 specimens and simulated soil electrolyte solution instability and its capacitance decreases,thus exacerbate the extent of corrosion.Under the CP voltage of-0.77 V(vs.SCE),with the AC interference voltage increasing from 1 V to 9 V,the arc of the Nyquist diagram of the capacitance gradually shrink,the charge transfer resistance(Rc) value decreases from 1669 Ω·cm2 without AC interference to reduce to 566 Ω·cm2 with 9 V AC interference,that is,accelerate the corrosion rate,thus reduce the degree of protection of the cathodic protection.The research also indicated that the method of improve the cathodic protection voltage will not be effective to inhibit AC interference.This study can provide strong scientific basis for design of CP system and evaluation of corrosion in presence of AC interference.