O_2浓度对钢在超临界CO_2中腐蚀速率的影响

Effect of O_2 Concentration on Corrosion Rate of Steels in Supercritical CO_2

研究了油气输送管道中常用的两种碳钢C75和X65及3种不锈钢13Cr,2205和904 L在80℃,12 MPa含有不同浓度O2的超临界CO2环境中的腐蚀行为。结果表明,当超临界CO2中O2浓度较低时,即使是微量O2(1.50×10-6),也能显著地加速碳钢和13Cr不锈钢的腐蚀;在O2浓度很高时(5.70×10-2)出现钝化现象,与不含O2时相比,无论碳钢还是13Cr不锈钢的腐蚀速率均降低;2205和904 L不锈钢的腐蚀均不受O2浓度的影响。

The carbon capture and storage(CCS) in geological reservoirs is now considered to be one of the main options for achieving deep reductions in CO2 emissions. Generally, the purity of captured CO2 is only about 95% and can contain trace gases such as O2, CO, SOxand NOx. In the presence of a water phase, these trace gases can contribute to the corrosiveness of high pressurehigh temperature CO2(supercritical CO2) systems. In this study, corrosion experiments of supercritical CO2 with various amounts of O2 were carried out to study the effect of small concentrations of O2 on the corrosion rate of two kinds of carbon steels C75 and X65 and three kinds of stainless steels 13 Cr, 2205 and 904 L in aqueous supercritical CO2 at 80 ℃ under 12 MPa. The decay kinetics of small starting O2 concentrations were investigated and used for the experiments with continuous replenishment of used-up O2. The results indicated that constant O2 concentrations in supercritical CO2, even trace of O2(1.50×10-6), could enhance the corrosion rate of carbon steels tremendously(more than 100 mm/a). Under this condition, even the corrosion rate of 13 Cr stainless steel obviously increased. However, surprisingly, with high O2 concentrations seemed to exhibit passivation effect and the corrosion rates for carbon steels and 13 Cr stainless steel were relatively low. The2205 and 904 L stainless steels were unaffected by addition of O2 and showed high resistance(<0.01 mm/a) to the aqueous supercritical CO2 corrosion.