磁场对NaCl溶液中X52管线钢腐蚀行为的影响

Effect of Magnetic Field on Corrosion Behavior of X52 Pipeline Steel in NaCl Solution

采用开路电位、极化曲线、电化学阻抗谱及腐蚀形貌观察等技术,研究了不同磁场强度(0、0.9、1.9及2.8 kA/m)对3.5%NaCl溶液中X52管线钢腐蚀行为的影响。结果表明:磁场使腐蚀电位负移、腐蚀电流密度增大、电荷转移阻抗减小,并一定程度上改变腐蚀形貌;磁场强度越大,对电化学腐蚀行为的影响越大。机理分析表明,磁场对电化学反应过程的影响由电极表面磁感应强度、磁感应梯度以及电解质中离子磁性、浓度等多因素综合决定;Lorentz力加速Fe^(2+)扩散、减小双电层厚度及Kelvins力对Cl^(-)作用而增加电极界面氧含量等腐蚀促进作用大于Kelvins力使Fe^(2+)在电极表面聚集的腐蚀抑制作用,从而整体上促进了电化学腐蚀。

Magnetic flux leakage internal inspection is the main method for detecting metal damage in oil and gas pipelines.After the magnetic flux leakage testing is implemented,there will exist a residual magnetic field in the pipeline for a long time.The influence of such residual magnetic field on the corro-sion behavior of the pipeline steel is not completely clear yet.Therefore,the influence of different magnet-ic field intensities(0.9,1.9 and 2.8 kA/m respectively)on the corrosion behavior of X52 pipeline steel in 3.5%NaCl solution was investigated by means of open circuit potential,polarization curves,electrochemi-cal impedance spectroscopy and corrosion morphology observation techniques.The results indicated that the presence of magnetic field can shift negatively the corrosion potential,increased the corrosion current density,reduced the charge transfer resistance,and changed the corrosion morphology to a cer-tain extent.The greater the magnetic field intensity,the greater the influence on the electrochemical corro-sion behavior.Through mechanism analysis,it follows that the influence of magnetic field on the electro-chemical reaction process may comprehensively be determined by multiple factors such as the magnetic flux intensity near the electrode surface,the magnetic field gradient,the ion-magnetism and-concentra-tion in the electrolyte.The Loren magnetic force can accelerate the diffusion of Fe^(2+)and reduce the thick-ness of the electric double layer,while the Kelvin force can increase the oxygen content of the electrode interface,all the above factors could promote the corrosion process,the effect of which may be stronger than the corrosion inhibition effect induced by that the Kelvin force causing Fe^(2+)to accumulate on the electrode surface,so that the electrochemical corrosion process was generally promoted.