碳钢在两种氯化物溶液中的极化行为

利用极化试验和交流阻抗试验研究了碳钢在0.5MNH4Cl和0.5MNaCl溶液中的点蚀行为;通过金相显微镜和电子探针对钢的腐蚀形貌进行观察。结果表明:碳钢在0.5MNaCl和0.5MNH4Cl溶液中的极化曲线都出现活化特征。随着溶液pH值的增加和NaHCO3的添加,碳钢在NH4Cl和NaCl溶液中极化曲线上均有活化、活化-钝化转变、钝化和点蚀特征。显微观察表明,钢中的夹杂物是主要的点蚀诱发源。碳钢在0.5MNaCl和0.5MNH4Cl溶液中形成的活化峰分别与形成沉积膜和络合物有关。

Polarization Behavior of Carbon Steel in Two Chloride Solutions

Pitting behavior of carbon steel in 0.5M NaCl and 0.5M NH4Cl solution was studied by means of polarization tests and AC impedance tests. Their corrosion characteristics had been determined by microscope and electron probe micro-analyzer （EPMA）. The results suggested that carbon steel exhibited active feature in 0.5M NaCl and 0.5M NH4Cl solution. While once pH value of NH4Cl was increased and NaHCO3 solution was added to NaCl solution, carbon steel behaved characteristics of activation, activationpassivation transition, passivation and pitting corrosion. It could be observed from microscopic observation and EPMA that pitting corrosion was initiated by inclusions in carbon steel. With increase of pH value and concentration of NaHCO3 solution, the stability of passive film formed on carbon steel became stronger and pitting corrosion potential became nobler. According to the electrochemical reaction, formation of active peak for carbon steel in two chloride solutions was related to complex and the intermediate product.