H2S薄层液膜下16Mn钢腐蚀的电化学研究

利用自行设计的测量金属在薄层液膜下腐蚀的三电极电化学电池,通过极化曲线和交流阻抗技术(EIS)研究了16Mn钢在含H2S薄层液膜下的电化学行为,并与之在大量H2S电解质溶液中的电化学行为进行了比较.结果表明:H2S促进了16Mn钢腐蚀的阴阳极过程;随着H2S浓度的升高,16Mn钢的自腐蚀电位(Ecorr)正移,腐蚀速率逐渐增加,但C(H2S)＞2 mmol/L后腐蚀速率不再增加;随薄层液膜酸度增加,Ecorr负移,自腐蚀电流(Jcorr)增大,但pH＜4.4后腐蚀速度与酸度无关.16Mn钢在H2S薄层液膜下与在全浸状态下的腐蚀机理可能不同.

Electrochemical Corrosion of 16Mn Steel Coated with Thin Electrolyte Film of Hydrogen Sulfide

An electrochemical cell with three electrodes was designed to study the effect of thin aqueous electrolyte layer on the electrochemical corrosion behavior of metals. The cell was used to investigate the electrochemical corrosion behavior of 16Mn steel coated with a thin electrolyte layer containing H_2S and compared with that in bulk aqueous solution of H_2S, making use of polarization curve technique and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion potential of 16Mn steel increased with increasing hydrogen sulfide concentration in the thin H_2S layer, while it increased with increasing concentration of H_2S but kept almost unchanged at a concentration of H_2S above 2 mmol/L. Moreover, the corrosion potential of the 16Mn steel decreased with decreasing pH value of the thin H_2S layer, while the corrosion current increased with decreasing pH value but kept almost unchanged at a pH value below 4.4. In general, the 16Mn steel coated with the thin electrolyte layer of H_2S might have different corrosion mechanism than that immersed in bulk aqueous solution of H_2S.