通过高温高压反应釜模拟普光气田集输环境, 研究H2S和CO2分压及Cl-浓度对普光气田用集输管线钢L360QCS钢腐蚀行为的影响。采用失重法测试腐蚀速率, 用四点弯曲法进行应力腐蚀试验, 结合宏观形貌观察和扫描电镜(SEM)微观观察及能谱(EDS)分析, 进行了综合研究。在H2S和CO2分压比固定的情况下, 随着H2S压力升高, 腐蚀速率先降后升。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, 氢鼓泡减少或者消失。腐蚀速率随着Cl-浓度的升高而增大, 达到临界值后, 腐蚀速率随着Cl-浓度的升高而降低; 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, 腐蚀产物的沉积可以抑制点蚀的生成, 从而使材料的应力腐蚀开裂敏感性降低。

The influences of partial pressure of H2S and CO2 and concentration of Cl- on corrosion behavior of L360QCS steel as gathering and transportation pipeline in sour environment simulating Puguang natural gas field were investigated in an autoclave. Weight-loss method and four point bending method were used to investigate the corrosion rate and SSCC(sulfide stress corrosion cracking ) susceptibility respectively. Microscopy, SEM and EDS were employed for studying the surface morphology, microstructure and composition of the corrosion products. At the same H2S/CO2, corrosion rate of L360QCS decreased at the beginning and increased later with the increase of sour gas pressure. Hydrogen blister was observed at a low pressure. When the pressure increased, the hydrogen blister was depressed and finally disappeared. There was a critical value of Cl-. When Cl- concentration was less than its critical value, the corrosion rate increased with increasing the Cl- concentration and the Cl- also induced pit corrosion and then SCC. Contrarily, when Cl- concentration was greater than the critical value, the deposition of corrosion products would improve the pitting corrosion resistance and thus reduce SCC susceptibility.