Study On Corrosion Behavior Of High-Strength Pipeline Steel Under The Coupling Of Stray Current And Stress

The stress factors such as residual stress,conveying pressure and ground pressure during the operation of the high-strength steel pipe line will cause elastic or plastic deformation of the pipeline,and the thermodynamic and dynamic processes of the pipeline corrosion will change.In addition,AC transmission lines,DC traction power supply systems,and high-voltage or ultra-high-voltage transmission systems are often laid in parallel or cross-over with pipelines,causing pipelines to be disturbed by stray currents,threatening the safe operation of high-strength steel pipelines.At present,the corrosion research on high-strength pipeline steel mostly focuses on corrosion caused by single factors such as stray current or stress,while the corrosion behavior of high-strength pipeline steel under multi-factor coupling is less studied.To this end,this paper carried out the corrosion study of high-strength pipeline steel under the coupling of AC stray current,DC stray current,stress level,soil conductivity and other factors.The corrosion rate test of pipeline steel under the action of AC and DC stray current was carried out by weight loss method.It was found that under the action of AC stray current alone,the corrosion rate of pipeline steel did not increase linearly with the increase of AC current density.However,the growth rate of corrosion is inhibited due to pitting or corrosion product film on the surface of the sample.Under the action of DC stray current alone,the corrosion rate increases linearly with the increase of DC current density,and the DC corrosion rate can reach 17 times of the AC corrosion rate,and its damage is far greater than the AC stray current.The concentration of AC corrosion is stronger,and it is easy to induce local pitting,which is easy to cause perforation behavior.Although the corrosion of DC stray electricity is much larger than AC stray current,DC corrosion is comprehensive and uniform corrosion.Under the coupling of AC and DC stray current,when the DC current density is constant,as the AC current density increases,the corrosion potential of the pipeline steel moves negatively,the corrosion current density increases,the anode Tafel slope increases,and the corrosion behavior increases.When the AC current density is constant,as the DC current density increases,the corrosion potential moves positively,the corrosion current density increases,and the offset amplitude of the corrosion potential is significantly larger than the AC current,indicating that the addition of DC stray current promotes the AC corrosion behavior of pipeline.After applying the same stray current interference,the soil conductivity is higher,the corrosion potential of the pipeline steel is more negative,the corrosion current density is larger,and the corrosion rate of the pipeline steel is larger.The higher the grade of pipeline steel,the stronger the corrosion resistance.Under the coupling of DC stray current and stress,as the stress level increases from 0 to 100%Y_s,the corrosion rate of pipeline steel continues to increase,which is positively correlated.Under the coupling of DC stray current and stress,the corrosion morphology of the sample surface is more serious than that of DC current.The diameter and depth of the corrosion pit increase,the number of pits increases,and the strip-shaped corrosion morphology appears.Based on the above research,the effects of AC stray current,DC stray current,stress level and soil conductivity on high-strength pipeline steel were studied by weight loss method and electrochemical test and surface analysis technology.The corrosion behavior law under the single action and coupling effect of each influencing factor is obtained.