NH_(4)^(+)浓度对N80钢在饱和CO_(2)的3%NaCl溶液中腐蚀行为的影响

Effect of NH_(4)^(+)Concentration on Corrosion Behavior of N80 Steel in CO_(2)-saturated 3%NaCl Solutions

利用失重法和电化学方法研究了N80钢在不同NH_(4)^(+)浓度下饱和CO_(2)的3%NaCl溶液中的腐蚀行为,通过SEM、3D轮廓仪、XRD和XPS对腐蚀形貌和腐蚀产物进行表征,阐释了腐蚀机理。结果表明,NH_(4)^(+)浓度对N80钢的腐蚀速率产生促进和抑制双重效果。当NH_(4)^(+)浓度为0~500 mg/L时,N80钢的均匀腐蚀速率随NH_(4)^(+)浓度增加而增加;当NH_(4)^(+)浓度增加至1000~2000 mg/L时,N80钢的均匀腐蚀速率随NH_(4)^(+)浓度增加而降低,且点蚀速率随NH_(4)^(+)浓度的变化规律与均匀腐蚀基本相同;当NH_(4)^(+)浓度为500 mg/L时,均匀腐蚀速率和小孔腐蚀速率最大。当NH_(4)^(+)浓度≤500 mg/L时,NH_(4)^(+)和Cl^(-)在金属表面发生了竞争吸附;当NH_(4)^(+)浓度大于500 mg/L时,NH_(4)^(+)在金属表面发生吸附对腐蚀起抑制作用。

NH_(4)Cl was one of the important factors causing corrosion of tubing steel in shale oil environment.Herewith,the effect of NH_(4)^(+)concentration on the corrosion behavior of N80 steel in 3%NaCl solution saturated with CO_(2)was studied by means of mass loss method,electrochemical methods,scanning electron microscope(SEM),3D profilometer,X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The results showed that NH_(4)^(+)concentration had a dual effect on the corrosion rate of N80 steel,i.e.promoting and inhibiting the corrosion rate.When the NH_(4)^(+)concentration was 0~500 mg/L,the uniform corrosion rate of N80 steel increased with the increasing NH_(4)^(+)concentration,while in the NH_(4)^(+)concentration range of 1000~2000 mg/L,the uniform corrosion rate of N80 steel decreased with the increasing NH_(4)^(+)concentration,however,the pitting corrosion rate showed a similar trend as the uniform corro-sion.When the NH_(4)^(+)concentration was 500 mg/L,the uniform corrosion rate and pitting corrosion rate of N80 steel were the highest.Competition adsorption occurred between NH_(4)^(+)and Cl^(-)on the metal surface at NH_(4)^(+)concentrations≤500 mg/L,while NH_(4)^(+)adsorption inhibited corrosion when NH_(4)^(+)concentration exceeded 500 mg/L.