元素硫对H2S + CO2饱和氯溶液中合金G3腐蚀的影响

The influence of elemental sulfur on the corrosion of Alloy G3 in H2S+CO2 saturated chloride solution

摘要:

本研究中利用电化学显微镜（SECM）、扫描电子显微镜（SEM）和电化学阻抗谱（EIS）研究了镍基合金G3在室温（25℃）和高温（90℃）、含H2S、CO2，Cl-介质环境中各种硫状态下的腐蚀行为。结果表明，随温度升高，腐蚀变得更加严重，镍基合金G3表面出现轻微的点蚀；阳极极化曲线在室温下具有钝化区，而在90℃的温度下出现活性溶解区，钝化现象消失。物相分析表明在镍基合金G3上形成钝化膜主要由Ni、Cr及Fe的氧化物组成，由于S2-侵入薄膜导致钝化膜溶解，腐蚀产物由NiS、FeS2组成。G3合金在含硫环境中的耐腐蚀性减弱，相比较沉积硫、析出硫，硫悬浮状态下镍基合金G3表面钝化膜最致密，腐蚀最轻微。研究表明硫是强催化剂，其存在导致严重的局部腐蚀，元素硫的状态是影响腐蚀产物膜的致密性和生长速率的关键因素，也是影响合金腐蚀速率的关键因素。

Abstract:

The corrosive behavior of the nickel-based alloy G3 at room temperature (25℃) and high temperature (90℃) in a complex medium environment containing H2S, CO2, Cl- with various states of elemental sulfur was studied by using electrochemical microscope (SECM), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) in this paper, and the influence of elemental sulfur was analyzed. The results show that the corrosion becomes more serious with increasing temperature and slight pitting occurs on the surface of the nickel-based alloy G3. The anode polarization curve has a passivation region at room temperature, but the active dissolution appears and passivation disappears at a temperature of 90℃. The phases were analyzed that the passivation film formed on the surface of the nickel-based alloy G3 is mainly composed of oxides of Ni, Cr and Fe. The passivation film is dissolved due to the intrusion of S2-, and the corrosion products were composed of NiS and FeS2. The corrosion resistance of G3 alloy is weakened in the sulfur-contained environment, and the suspended sulfur has the most dense passivation film and the least corrosion rate compared with the deposition of sulfur and the precipitation of sulfur. Studies have shown that sulfur is a strong catalyst, and its existence leads to severe local corrosion. The state of elemental sulfur is a key factor affecting the compactness and growth rate of corrosion product membranes and the corrosion rate of alloys.