Study On The Anti-Hydrogen Sulfide Corrosion Of Pipeline Steel

Pipeline steel is the main material of transmission pipeline for oil and natural gas. However, oil and natural gas often contains large amounts of hydrogen sulfide gas. Hydrogen sulfide gas in a wet environment will form an acidic aqueous solution of hydrogen sulfide which can easily cause pipeline corrosion. The corrosion of hydrogen sulfide gas to pipeline transport brings enormous security risks and economic losses. Therefore, how to improve the resistance to hydrogen sulfide corrosion is a significant topic.The addition of alloying elements is one effective manner to improve pipeline resistance to hydrogen sulfide corrosion. Therefore, this article chooses X80 pipeline steel which is applied universally domestic and abroad currently for the study. Reference GB smelting, forging and rolling, pipeline steel is made with the different amount of alloying steel. By the means of accelerated corrosion test in H2S-NACE saturated solution and electrochemical experiments, this paper invested the influence laws of rare earth, molybdenum, niobium and other alloying elements on the pipeline resistance to hydrogen sulfide corrosion and electrochemical characterization. Research to further improve the resistance to hydrogen sulfide corrosion pipeline has some theoretical significance.In our experimental conditions, the main conclusions were discussed:(1) The appropriate addition of RE can significantly improve the resistance to hydrogen sulfide corrosion pipeline, while the effect of molybdenum and niobium is less obvious.In this test steel's composition range, when the rare earth content of 0.018%, the resistance of pipeline to hydrogen sulfide corrosion is best.(2) The surface of pipeline in the corrosion process can produce two kinds of rust layers. One was the shedding of the porous honey-comb rust layer mainly composed of iron oxides and sulfide. The other one was the compact rust layer which is close to the matrix, mainly composed of iron sulfides.(3) At the frist stage of corrosion test, because of the formation of honey-combrust layer, the corrosion rate was relatively high as therust layer was thick. At the second stage, rust layer honey-comb began to resolve, the rust layer thickness greatly reduced, and due to the compact layer of rust protection effect, the corrosion rate significantly reduced.(4) The right amount of the addition of RE can significantly improve the electrochemical stability of the pipeline, makeing the pipeline corrosion potential increase and the corrosion current density reduce, thereby increasing the RE effectively improved the pipeline of anti-hydrogen sulfide corrosion. The change of molybdenum and niobium content on the effect to electrochemical stability of the pipeline is unobvious.(5) The compact rust layer promoted the pipeline's corrosion potential and decreased the corrosion current density, which significantly improved electrochemical stability.