海洋环境下金属管道力-腐蚀电场耦合特性分析

Characteristic analysis of the coupling stress-electric field of metal pipe corrosion under marine environment

对于存在预紧力和腐蚀缺陷的金属管道,在缺陷处经常发生局部弹塑性形变,并影响金属管道的腐蚀电场特性。以存在椭球形腐蚀缺陷的20#钢金属管道为研究对象,建立了金属管道弹塑性应力应变与局部电化学腐蚀的力学-电化学耦合模型,研究了不同拉伸位移对金属管道应力分布和腐蚀电场特性的影响。结果表明,不同拉伸位移下,Mises应力、腐蚀电位、腐蚀电流密度和腐蚀电场模值大小均相对缺陷中心对称分布,最大值均出现在腐蚀缺陷中心处,且数值均随着拉伸位移增大而增大。塑性变形阶段对缺陷局部电化学特性的影响显著大于弹性变形阶段。腐蚀缺陷处的腐蚀由一系列微小原电池组成,拉伸位移增大将加快缺陷处腐蚀速度。

For metal pipe with pretension and corrosion defects,local elastic-plastic deformation often occurs at the defects and affects the corrosion electric field characteristics of the metal pipe.This paper takes 20#steel metal pipe with ellipsoidal corrosion defect as the research object,and establishes a mechanical-electrochemical coupling model of elastic-plastic stressstrain and local electrochemical corrosion to study the effects of different tensile displacements on stress distribution and corrosion electric field characteristics of metal pipes.The results show that mises stress,corrosion potential,corrosion current density and corrosion electric field mode are symmetrically distributed with respect to the defect center under different tensile displacements,with the maximum value occurring at the defect center,and the values all increase with the increase of tensile displacement.The influence of plastic deformation stage on the local electrochemical characteristics of defects is significantly greater than that of elastic deformation stage.The corrosion at the defect is composed of a series of small galvanic cells,and the increase of tensile displacement can accelerate the corrosion rate at the defect.