恒电流脉冲法研究钢筋在模拟混凝土孔溶液中的腐蚀行为

Steel corrosion in simulated concrete pore solutions using a galvanostatic pulse method

通过恒电流脉冲法研究了钢筋在不同pH值模拟混凝土孔溶液中的腐蚀行为.应用时间常数与双电层电容计算了钢筋的极化电阻.结果表明:钝化钢筋的时间常数大于活化腐蚀钢筋,钝化钢筋的双电层电容比活化腐蚀钢筋小;腐蚀末期较好的抗腐蚀能力证实了钢筋在CP模拟液(pH13·6)中形成的钝化膜比在CH模拟液(pH12·5)中更致密,耐蚀性更好,而在CN模拟液(pH11·0)中基本无法形成完整的钝化膜;SO2-4与SiO2-3加入CP模拟液能提高钢筋的极化电阻,钢筋表面形成了更致密的钝化膜,在腐蚀末期钢筋表现出了更好的耐蚀性.最后,比较了恒电流脉冲、线性极化及电化学阻抗谱所测的极化电阻与腐蚀电流密度,表明这三种电化学方法在测试钢筋腐蚀速率方面具有较好的相关性.

Corrosion behaviors of steel in simulated concrete pore solutions with different pH values were investigated by means of a galvanostatic pulse method（GPM）.The polarization resistance of steel was derived from time constant and double layer capacitance in GPM.The time constant value of passive steel is higher than that of active steel,while the double layer capacitance of passive steel is relatively lower than that of active steel.The better anti-corrosion capacity in the final corrosion period confirms that the steel exposed to CP solution（pH 13.6） has a better passive film than that exposed to CH solution（pH 12.5）,but there is not any passive film on the steel exposed to CN solution（pH 11.0）.The addition of SO2-4 and SiO2-3 into CP solution increases the polarization resistance,promoting the passivation of steel,especially in the corrosion period.Finally,the polarization resistance values measured by GPM were compared with the results of linear polarisation resistance（LPR） and electrochemical impedance spectroscopy（EIS）.It is found that the correlation is acceptable for these electrochemical methods in evaluating the corrosion rate of steel in simulated concrete pore solutions.