静水压力对X100钢在NaHCO_3+NaCl溶液中电化学行为的影响

Effect of Hydrostatic Pressure on Electrochemical Behavior of X100 Steel in NaHCO_3+NaCl Solution

采用动电位极化、电化学阻抗谱和Mott-Schottky等电化学测量方法研究了静水压力对X100管线钢在0.5 mol/L Na HCO3+0.03 mol/L Na Cl溶液中的电化学腐蚀行为的影响。结果表明:随静水压力增加,X100钢表面点蚀坑数量和面积增加;静水压力增加使溶液离子的活性增加,促进Cl-在钝化膜中的吸附,腐蚀反应的速率加快,腐蚀电流密度增加。静水压力增加使钝化膜组成由低压时的氧化物或氢氧化物转变为高压时的碳酸盐,导致耐蚀性降低,而点蚀形核几率增加。X100管线钢钝化膜具有n型半导体性质,随静水压力的增加,钝化膜内Cl-的增多使晶格缺陷增多,促进了氧化膜的破裂。

Effect of hydrostatic pressure on the electrochemical corrosion of X100 pipeline steel in0.5 mol/L Na HCO_3＋ 0.03 mol/L Na Cl solution was investigated by means of methodspotentindynamic polarization, electrochemical impedance spectroscopy and Mott- Schottky. The results show that with the increasing hydrostatic pressure the number and the size of corrosion pits increase,while the activity of ions in the solution also increases, which in turn promotes the adsorpting of Clin the passive film. As a result, the corrosion rate and the corrosion current density are increased.The component of the passive film transforms from oxide or hydroxide formed by low pressures to carbonate by high pressures, which may result in the decrease of corrosion-resistance and increase of probability of pitting corrosion nucleation. The passivation film formed on the X100 steel exhibits characteristics of n-type semiconductor. The increase amount of Cl^- in the passivation film promotes the increase of lattice imperfections and facilitates the cracking of the oxide film.