某凝析气田异种不锈钢偶对在不同NaCl溶液中的腐蚀行为

为了考察某凝析气田现场新投用的3种合金钢材316L、双相不锈钢2205以及Inconel 625在现场出现耦合后是否会发生电偶腐蚀,对Inconel 625/316L、Inconel 625/2205偶对在不同Cl~-浓度下的电偶腐蚀特性进行了电化学试验,研究了耦合前各自的开路电位随时间的变化、耦合后的耦合电流随时间的变化、耦合(闭路)电位随时间的变化、耦合电流及耦合(闭路)电位的稳定值大小。结果表明:不同影响因素(电偶、Cl~-浓度)下,电位差均为50 mV左右,电偶电流密度约为1×10~(-6)A/cm~2,由此计算出材料偶接后的均匀腐蚀速度为0.002 mm/a,按照腐蚀速度划分标准(NACE RP0775-2005),均属于轻度腐蚀,因此625/316L、625/2205异种不锈钢之间耦合不会引起明显的电偶腐蚀问题。本方法对在油气田上使用类似异种钢耦合后出现的腐蚀研究具有一定的指导意义。

Corrosion Behavior of Dissimilar Stainless Steel Pairs of a Condensate Gas Field in Different NaCl Solutions

In order to study the galvanic corrosion of dissimilar steel pairs like Inconel 625/316L and Inconel 625/2205,galvanic corrosion ex periments of Inconel 625/316L and Inconel 625/2205 were performed under different C1-concentrations.The experiment contents mainly included the changes of open circuit potential,coupling current and coupling potential (closed circuit) before and after coupling reaction,and their steady values after coupling reaction (closed circuit).Results showed that in different factors (galvanic,chloride ion concentration),all of the potential difference was about 50 mV and the coupling current density was about l× 10-6 A/cm2,so the uniform corrosion rate of the material was calculated as 0.002 mm/a.According to the corrosion rate division standard (NACE RP0775-2005),the corrosion rate was mild,so the coupling between 625/316L and 625/2205 dissimilar stainless steel did not cause obvious galvanic corrosion problems.This paper presented certain guiding significance on the study of corrosion of the coupling of dissimilar steels in the field of oil and gas field.