湿气环境中CO_(2)-H_(2)S在α-Fe(110)密排面上吸附与点蚀机理研究  

Adsorption and Corrosion Mechanism of CO_(2)-H_(2)S onα-Fe(110)Close-packed Plane in Humid Environment

作　　者：李金灵[1,2] 马文骏 朱世东[3,4] 屈撑囤[1,2] 付安庆 LI Jinling;MA Wenjun;ZHU Shidong;QU Chengtun;FU Anqing(Shaanxi Province Key Laboratory of Environmental Pollution Control and Reservoir Protection Technology of Oilfields,College of Chemistry and Chemical Engineering,Xi'an Shiyou University,Xi'an 710065,China;Shaanxi University Engineering Research Center of Oil and Gas Field Chemistry,Xi'an Shiyou University,Xi'an 710065,China;School of Materials Science and Engineering,Xi'an Shiyou University,Xi'an 710065,China;Key Laboratory of Corrosion Protection and New Materials for Oil and Gas Fields of Shaanxi Higher Education Institutes,Xi'an Shiyou University,Xi'an 710065,China;National Key Laboratory of Oil and Gas Drilling and Transportation Equipment,CNPC Tubular Goods Research Institute,Xi'an 710077,China)

机构地区：[1]西安石油大学化学化工学院、陕西省油气田环境污染控制技术与储层保护重点实验室 [2]西安石油大学油气田化学陕西省高校工程研究中心,西安710065 [3]西安石油大学材料科学与工程学院,西安710065 [4]西安石油大学油气田腐蚀防护与新材料陕西省高等学校重点实验室,西安710065 [5]油气钻采输送装备全国重点实验室中国石油集团工程材料研究院有限公司,西安710077

出　　处：《表面技术》2024年第20期82-93,共12页Surface Technology

基　　金：国家自然科学基金(51974245,52071338);西安市科技计划(24GXFW0077);中国石油集团科技开发项目(2022DQ0527)。

摘　　要：目的从微观尺度探究CO_(2)-H_(2)S(CO_(2)和H_(2)S共存)在湿气管道顶部的吸附特性,进而揭示点蚀机理。方法基于密度泛函理论的第一性原理,利用Materials Studio构建CO_(2)、H_(2)S和CO_(2)-H_(2)S在α-Fe(110)密排面的吸附模型,对CO_(2)、H_(2)S和CO_(2)-H_(2)S在α-Fe(110)面的吸附能、局域态密度、分波态密度和差分电荷密度进行仿真;利用高温高压釜模拟CO_(2)-H_(2)S-Cl^(-)腐蚀环境,分析L360钢在湿气环境中的腐蚀行为;最后,揭示含Cl^(-)湿气管道顶部CO_(2)-H_(2)S吸附机制与点蚀机理。结果CO_(2)、H_(2)S、CO_(2)-H_(2)S及CO_(2)-H_(2)S-Cl^(-)在最稳定位置时的吸附能分别为-4.065、-3.961、-8.538、-12.775e V,表明相较于CO_(2)与H_(2)S单独吸附,CO_(2)-H_(2)S在α-Fe(110)面的吸附能更负,Cl^(-)会进一步降低CO_(2)-H_(2)S的吸附能;且CO_(2)在与H_(2)S竞争环境电子中占优势;Cl^(-)会使CO_(2)-H_(2)S的局域态密度峰值降低,转移趋势为失去电子,基体和腐蚀介质的电子向着低能级跃迁释放出更多能量,进而加强了Fe与CO_(2)-H_(2)S间的化学键强度;Cl^(-)的2p轨道与Fe的3d轨道在-6.8 eV和-5.7 eV发生重叠,Cl^(-)被吸附到Fe表面并与Fe形成化学键生成氯化物,进而改变腐蚀产物膜的组分与结构,削弱产物膜的致密性和稳定性,减弱腐蚀阻抗力。在含Cl^(-)湿气的CO_(2)-H_(2)S环境中,液相中的Cl^(-)浓度升高,使L360钢的气相平均腐蚀速率逐渐增大,最高达2.935mm/a,点蚀越发严重。结论CO_(2)与H_(2)S在α-Fe(110)面吸附存在一定的协同和竞争作用,协同促进金属的腐蚀,FeCO3会优先沉积成膜,但H_(2)S会抑制FeCO3的生长,腐蚀产物以FeS为主;Cl^(-)会增强CO_(2)-H_(2)S与α-Fe(110)面间的作用力,弱化腐蚀产物膜层的保护性,进一步加速金属腐蚀、尤其是点蚀。CO_(2)and H_(2)S gas and the droplets containing Cl^(-)often co-exist on the top of the pipelines used for transporting oil and gas,which is different from the bottom environment of the pipelines,resulting that the corrosion processes are complex and the pipelines suffer from more serious local corrosion.Up to now,there are numerous studies about the effects of CO_(2)or/and H_(2)S on pipeline corrosion,but most of them mainly focus on the corrosion protection and control,material selection and corrosion protection systems,etc.,there are relatively few reports on the generation and evolution of corrosion from the perspective of theory,especially from the electron structure at the microscopic level.While revealing the mechanism of corrosion occurrence and evolution from the microscopic level is an important basis for formulating effective anti-corrosion measures.In this paper,the adsorption and corrosion characteristics of CO_(2)-H_(2)S on theα-Fe(110)close-packed plane in the humid environment containing Cl^(-)were studied,and the adsorption and pitting mechanism was explored from the microscopic scale,in order to provide theoretical basis for the corrosion mechanism study and effective protection technology application of pipelines in oil and gas fields.Based on the first-principle method of Density Functional Theory(DFT),Materials Studio software was applied to establish an adsorption model of CO_(2),H_(2)S and Cl^(-)onα-Fe(110)surface.The adsorption energy,local density of states(LODS),partial density of states(PDOS)and differential charge density of CO_(2),H_(2)S,CO_(2)-H_(2)S and CO_(2)-H_(2)S-Cl^(-)onα-Fe(110)surface were calculated,respectively.The results showed that the adsorption energy of CO_(2),H_(2)S,CO_(2)-H_(2)S and CO_(2)-H_(2)S-Cl^(-)at the most stable position ofα-Fe(110)was−4.065 eV,−3.961 eV,−8.538 eV and−12.775 eV,respectively indicating that the adsorption energy of CO_(2)-H_(2)S on theα-Fe(110)surface was more negative than that of CO_(2)and H_(2)S alone,and Cl^(-)further reduce

关 键 词：CO_(2)-H_(2)S Cl^(-) 第一性原理 α-Fe(110)密排面 吸附特征 腐蚀机理 

分 类 号：TE88[石油与天然气工程—油气储运工程]