电极工作面积和孔隙液pH值对钢筋脱钝临界氯离子浓度的影响

基于模拟混凝土孔隙液中的钢筋脱钝试验,揭示了钢筋电极的工作面积和模拟混凝土孔隙液的pH值对钢筋脱钝过程中开路电位、极化电阻和腐蚀电流密度的影响规律,确定了不同钢筋电极工作面积和pH值条件下钢筋脱钝的临界氯离子浓度,分别建立了钢筋电极工作面积和模拟混凝土孔隙液pH值与钢筋脱钝临界氯离子浓度之间的定量关系.结果 表明:随着钢筋电极工作面积的增大,钢筋脱钝的临界氯离子浓度降低;随着模拟混凝土孔隙液pH值的增加,以自由氯离子浓度Cl-]表征的临界氯离子浓度增加,而以Cl-]/OH-]表征的临界氯离子浓度降低;与开路电位和极化电阻相比,钢筋脱钝过程中腐蚀电流密度的突变点更加明显.

Influence of Working Area of Electrode and pH Value of Pore Solution on Critical Chloride Concentration for Steel Bar Depassivation

Based on depassivation experiments of steel bar in simulated concrete pore solution, the influences of working area for steel electrode and pH value for simulated concrete solution on open-circuit potential, polarization resistance and corrosion current density during depassivation process were investigated. The critical chloride concentration of steel bar under different conditions of working areas and pH values were determined. The quantitative relationship between the critical chloride concentration and the working area as well as pH value were established respectively. Analysis results show that the critical chloride concentration decreases with the increase of working area of steel electrodes. The chloride ion concentration corresponding to inflection points of open-circuit potential, polarization resistance and corrosion current density decrease with the increase of working area of steel electrodes and the decrease of pH value for simulated concrete pore solution. The critical chloride concentration in terms of free chloride ion concentration Cl?] increases with the increase of pH value for simulated concrete pore solution, while the critical chloride concentration in terms of Cl?]/OH?] decreases with the increase of pH value for simulated concrete pore solution. Comparing with open-circuit potential and polarization resistance, the inflection point of corrosion current density is more obvious during the depassivation process of steel bar.