Study On Stray Current Corrosion Mechanism And Residual Strength Of Buried Pipeline

With the rapid development of rail transit has become a major strategic requirement in China,while resolving the traffic pressure,it also brings new problems.The stray current generated by rail transit operation seriously threatens the service safety of buried pipelines along the track.For buried steel pipelines around rail transit,serious electrochemical corrosion will occur when stray current flows in,resulting in pipeline corrosion,perforation,leakage and explosion accidents.Therefore,in-depth analysis of stray current corrosion mechanism and study of residual strength and residual life of stray current corrosion pipelines are of great significance for corrosion protection of buried pipelines.The numerical simulation method was applied to the study of stray current corrosion.The electrochemical corrosion module in COMSOL software was used to analyze the density,distribution and influence of stray current near the pipe-ground interface under specific conditions.The secondary current interface in COMSOL was used to model a pipeline in soil.The electrochemical reaction of stray current corrosion of buried pipeline was simulated.The electrode reaction process of stray current corrosion under different pipe-to-ground potential and soil conductivity was studied.The results show that in the process of stray current corrosion of buried pipelines,the stray current intensity is most significantly affected by the geopotential of the pipeline,followed by the soil conductivity.Oxygen reduction reaction current density,oxygen evolution reaction current density and iron oxidation reaction current density are significantly affected by tube ground potential.Based on the simulation of stray current corrosion,the effect of stray current on the corrosion behavior of buried pipelines was studied by means of polarization curve and impedance techniques through indoor electrochemical experiments,and the corrosion rates of buried pipelines under different reaction conditions were calculated.The test results show that the corrosion potential of buried pipeline will shift negatively with the increase of stray current intensity,and the self-corrosion electrorheology will increase with the increase of stray current voltage.In addition,in the corrosive environment,the movement of charged particles is accelerated.Hydrogen gas is generated during the reaction process.Hydrogen bubbles are precipitated on the metal surface,which destroys the anti-rust coating and accelerates the corrosion of the pipeline again.On the basis of electrochemical corrosion experiments and combined with stray current corrosion evaluation criteria,residual strength of defective pipelines corroded by stray current was studied by finite element method,and residual life of defective pipelines was calculated.The effects of different types and sizes of stray current corrosion defects on the residual strength of pipelines are analyzed.The results show that pitting corrosion pits and corrosion depth have the greatest impact on the residual strength of pipelines.