H2S/CO2共存环境中施加应力与介质流动对碳钢腐蚀行为的影响

采用带有磁力驱动轴的高温高压腐蚀测试釜,通过失重法研究了施加应力与介质流动对20#钢和L245NS钢在H2S/CO2共存环境中腐蚀行为的影响。采用SEM和XRD表征手段分析了浸泡腐蚀后四点弯曲试样表面的微观形貌及腐蚀产物的组成。结果表明:在H2S/CO2共存环境中的各实验条件下,20#钢的平均腐蚀速率均高于L245NS钢的。当施加应力和液态介质流动时,两种材料的腐蚀速率均增大;应力对腐蚀速率的影响更显著。推测腐蚀机理为:H2S在腐蚀过程中起主导作用,生成了具有保护性的FeS腐蚀产物膜。应力会导致腐蚀产物膜存在大量微观通道,促进了腐蚀过程的进行;流体流动加速了金属溶解和腐蚀性物质的扩散,表现出最大的腐蚀速率。

Effect of Applied Stress and Medium Flow on Corrosion Behavior of Carbon Steel in HS/CO Coexisting Environment

The effect of applied stress and medium flow on the corrosion behavior of 20# steel and L245 NS steel in H2 S/CO2 co-existence environment was studied by mass loss method using high-temperature and high-pressure corrosion test kettle with magnetic drive shaft. Then, the surface morphology and composition of corrosion products of the four-point bending specimens after immersion corrosion were characterized by means of SEM and XRD. Results show that the average corrosion rate of 20# steel is higher than that of L245 NS steel in H2 S/CO2 containing medium. When a stress is applied on the test piece and/or the medium flows, the corrosion rate of both materials increases. The effect of stress on corrosion rate is more significant. The corrosion mechanism is speculated as follows: H2 S plays a leading role in the corrosion process and produces a protective FeS corrosion product film. The stress will lead to the formation of a large number of microscopic channels in the corrosion product film, which promotes the corrosion process. Fluid flow speeds up the dissolution of metals and the diffusion of corrosive substances, resulting in enhanced corrosion rates.