H_2S/CO_2分压和Cl^-浓度对L360QCS腐蚀行为的影响研究

STUDY ON THE EFFECT OF H_2S AND CO_2 PARTIAL PRESSURE AND Cl^- CONCENTRATION ON L360QCS CORROSION

通过高温高压反应釜模拟普光气田集输环境,研究H2S/CO2分压、Cl-浓度对普光气田用集输管线钢L360QCS腐蚀行为的影响。采用失重法计算腐蚀速率,四点弯曲法进行应力腐蚀试验,宏观形貌观察和扫描电镜(SEM)微观观察及能谱(EDS)分析进行综合研究。在H2S/CO2分压比固定的情况下,随着H2S压力升高腐蚀速率呈现先降后升。压力较低时,L360QCS应力腐蚀试样表面均出现不同程度的氢鼓泡,当压力升高时,氢鼓泡很少或者消失。腐蚀速率随着Cl-浓度的升高而增加,达到临界值后,腐蚀速率随着Cl-浓度的增加而降低;在低浓度条件下,Cl-浓度的增加会促进点蚀的发生,进而诱发裂纹的产生;而当Cl-浓度增加到临界值时,抑制点蚀的生成,从而使材料的应力腐蚀开裂敏感性降低。

The influence of H2S/CO2 partial pressure and Cl-concentration on L360QCS corrosion was investigated by simulating the environment of Puguang gas field gathering and transportation pipeline.Weight-loss method,four point bending method were used to calculate the corrosion rate and SCC susceptibility respectively.And microscope,SEM and EDS were used to study the surface morphology,microstructure and composition of the corrosion products.Under the circumstances of fixed H2S/CO2 partial pressure ratio,corrosion rate of L360QCS decreased at the beginning and then increased later with the increasing of H2S pressure,hydrogen blister was observed when pressure was lower.When the pressure increased,the hydrogen blister reduced and finally disappeared.If Cl-concentration was less than the critical concentration,the corrosion rate increased with the increase of Cl-concentration,the Cl-also induced pit corrosion.Contrarily,when Cl-concentration was greater than the critical value,Cl-improved the pitting corrosion resistance and decreased SCC susceptibility.