温度对3%Cr管线钢CO_2腐蚀产物膜的影响

经济型低Cr合金钢具有较好的抗CO2腐蚀性能,利用高温高压反应釜研究了3%Cr管线钢的CO2腐蚀行为,采用X射线衍射(XRD)、扫描电镜(SEM)和能谱仪(EDS)等对腐蚀产物膜的微观形貌、化学成分以及结构进行分析,探讨了温度对3%Cr管线钢腐蚀产物膜的影响.结果表明,CO2分压0.8 MPa、液体流速1.0 m.s-1时,在40～140℃范围内,3%Cr管线钢均未发生局部腐蚀,其平均腐蚀速率呈先升高后降低的趋势,峰值温度在100℃左右.3%Cr管线钢的腐蚀产物膜具有两层结构:内层膜为致密的富Cr层(Cr富集程度可高达Cr/Fe=8/5),主要由含Cr化合物和非晶态FeCO3构成,并随着温度的升高,Cr富集程度增加,内层膜厚度降低;外层膜则由晶态FeCO3堆积而成.

Effect of temperature on CO2 corrosion production scales on 3%Cr pipeline steel

Economic low-chromium steels show superior resistance to CO2 corrosion.The corrosion performance of 3%Cr pipeline steel was studied with a high-temperature and high-pressure autoclave.In a CO2 environment,X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy-dispersive spectrometry(EDS) were used to analyze the morphologies and characteristics of corrosion production scales on 3%Cr steel.The formation of the scales at different temperatures was also discussed.The results show that when the CO2 partial pressure is 0.8 MPa and the flow velocity is 1.0m·s-1 within the temperature range of 40 to 140 ℃,the average corrosion rate first increases and then decreases with increasing temperature,and its maximum can be obtained at about 100 ℃.For all the test conditions no localized corrosion was observed.There is a two-layer structure in the scales.The inner layer,which is mainly composed of Cr compounds and amorphous FeCO3,is denser and more stable because of Cr enrichment.The Cr content of the inner layer increases with increasing temperature and the mass ratio of Cr to Fe can reach 8/5.The outer layer is formed from the precipitation of crystalline FeCO3.