| With the rapid development of the world economy and the continuous improvement of environmental protection requirements,the development of clean energy has attracted more and more attention.The large gas fields currently developed in my country,such as Puguang and Kela,are all（high）sulfur-containing natural gas fields.During their development,due to the decrease in temperature and pressure,the solubility of elemental sulfur（elemental sulfur）in H2S is reduced and precipitated.It also deposits on the surface of pipeline steel and causes corrosion to pipeline steel in the H2S-CO2-Cl-coexisting corrosion system.The perforation and leakage of pipeline steel are major safety hazards for natural gas gathering and transportation pipelines.Exploring the corrosion mechanism of elemental sulfur in gathering and transportation pipelines,especially the pitting corrosion mechanism,is of great significance for establishing corrosion control measures.In this paper,the weight loss method was used to study the corrosion behavior of L360steel in the H2S-CO2-Cl-coexisting corrosion system under temperature,corrosion time,Cl-concentration and S content.The corrosion product film was studied by SEM,XRD and other characterization methods.For the morphology and composition,three electrochemical testing methods including electrokinetic potential scanning,electrochemical impedance spectroscopy,and cyclic polarization curve are used,combined with corrosion morphology,to study the effects of reaction temperature,reaction time,Cl-concentration and elemental S content on L360 steel The influence of electrochemical corrosion behavior;and the mechanism of pitting corrosion is revealed,and the main conclusions are as follows:（1）The corrosion rate of L360 steel gradually increases with the increase of the corrosion temperature.When the corrosion temperature is 60℃,the corrosion rate is the largest,which is 0.48822 mm/a,and its pitting corrosion pits also increase with the increase of the corrosion temperature.Gradually increase.The cyclic polarization curve shows that as the reaction temperature increases,the breakdown potential Ebvalue decreases,the protection potential Epvalue decreases,and the Eb-Epvalue increases.When the corrosion temperature is60℃,the Ebof L360 steel is the smallest,which is 0.7395 V,The minimum value of and Epis0.4189V,and the value of Eb-Epis the maximum value,0.3505V,which means that when the reaction temperature is 60℃,the resistance to pitting corrosion of L360 steel decreases,and pitting corrosion is more likely to occur.（2）The corrosion rate of L360 steel increases with the increase of the reaction time.When the reaction time is 14d,the corrosion rate is the largest.From the potential scanning curve and the cyclic polarization curve,it can be found that with the increase of the corrosion time,the self-corrosion potential has a negative shift.When the reaction time is 14d,the Ecorrvalue is the smallest,which is-0.5707V.At this time,the point of L360 steel The corrosion tendency is the greatest,the stability of the product film of the substrate is the weakest,and the product film has the weakest protection to the collective.（3）The corrosion rate of L360 steel increases with the increase of Cl-concentration in the solution.When the Cl-concentration is 40g/L,the corrosion rate of L360 steel has a maximum value of 0.4882 mm/a.It can be seen from the impedance spectrum that the impedance spectrum is a semicircle of a single capacitive reactance arc,showing capacitive reactance characteristics.With the increase of Cl-concentration,the radius of the capacitive reactance arc decreases,indicating that the increase of Cl-concentration makes L360 stainless steel During the electrochemical reaction,the resistance is reduced,the corrosion resistance is reduced,the stability of the passivation film becomes worse,and the corrosion is accelerated.（4）The presence of elemental sulfur greatly promotes the corrosion of L360 steel in the H2S-CO2-Cl-system,and with the increase of elemental sulfur content,the corrosion rate of L360 steel first increases and then decreases.The corrosion rate is the largest at 20 g/L,which is 1.53439 mm/a.The Ecorrof L360 steel gradually shifts negatively with the increase of the elemental S content.When the elemental sulfur content is 20 g/L,the Ecorrof L360 steel is the smallest at-0.4368V,and the corrosion current density(Icorr)is the largest at 8.9768×10-5A·cm-2,from a dynamic point of view,the larger the Icorr,the faster the corrosion rate.With the increase of the elemental S content in the corrosion system,the EIS maps mostly show two capacitive arcs and pitting corrosion characteristics.This shows that the corrosion surface film of L360 steel has been ruptured to varying degrees after elemental sulfur is added.Pitting corrosion occurs.At this time,the film resistance（Rf）and the charge transfer resistance（Rt）are obviously reduced,the protection of the passivation film is reduced,and the corrosion rate increases.When the S content continues to increase to 50 g/L,Rtstarts to increase gradually,and the corrosion rate starts to decrease.（5）When elemental sulfur is not added to L360 steel,the reaction mechanism is electrochemical corrosion mechanism.After elemental sulfur is added,the reaction mechanism becomes electrochemical corrosion mechanism and direct corrosion mechanism. |
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