迁移型阻锈剂对混凝土中钢筋的长期影响

Long-term Effects of Migrating Corrosion Inhibitors on Steel Bars in Concrete

采用含有迁移型阻锈剂(MCI)的模拟混凝土孔溶液模拟施用MCI的钢筋混凝土,利用孔溶液中阻锈剂浓度的递减模拟MCI向外部扩散,利用孔溶液中pH值的递减模拟混凝土的碳化,以研究MCI对混凝土中钢筋的长期影响。考虑MCI的类型(醇胺类的N,N-二甲基乙醇胺DMEA和氨基羧酸类的乙二胺四乙酸四钠EDTA-4Na)和浓度(0.1 mol·L^-1和0.05 mol·L^-1)的影响,并采用电化学阻抗谱测试、动电位极化曲线测试研究钢筋阻抗和腐蚀速率随MCI浓度和溶液pH值的变化情况。研究结果表明:初始模拟孔溶液中的MCI浓度对DMEA的耐久性能有一定的影响,最初采用的MCI浓度越高,钢筋表面吸附层越致密,越不易受溶液中MCI浓度降低的影响,而EDTA-4Na对钢筋的阻抗有削弱作用,当溶液中EDTA-4Na浓度降低时反而出现了阻抗增加现象;当pH值降低时,DMEA在钢筋表面的吸附层有脱附现象,钢筋的阻抗降低,腐蚀电流密度增大,EDTA-4Na的阻锈作用增强,钢筋的阻抗增大,腐蚀电流密度降低;DMEA的阻锈性能较稳定,当溶液中MCI浓度和pH值降低时钢筋始终处于钝化状态;EDTA-4Na不能提供稳定的阻锈作用,钢筋大部分时期处于脱钝状态。

Simulated concrete pore solution with migrating corrosion inhibitor(MCI)was adopted to simulate reinforced concrete applied MCI and the decreases of MCI concentration and pH value in pore solution were used to simulate the outward diffusion of MCI and carbonation respectively,with the aim of studying the long-term effects of MCI on the passivated steel bars in concrete.The influences of MCI types(amino alcohol based N,N-dimethylethanolamine DMEA and amino carboxylate based ethylenediaminetetraacetic acid tetrasodium salt EDTA-4Na)and MCI concentrations(0.1 mol·L^-1 and 0.05 mol·L^-1)were investigated.The evolutions of impedance and corrosion rates of steel bars with MCI concentration and pH were studied by electrochemical impedance spectroscopy and potentiodynamic polarization curve tests.The study results show that initial concentration has an effect on the durability of DMEA and the higher the MCI concentration used initially,the more uniform the adsorbing layer on the surface of the steel bar,and the less sensitive to the decrease of the surrounding MCI concentration.However,EDTA-4Na weakens the impedance of the steel bar when the MCI concentration decreases.As pH decreases,the adsorption layer of DMEA desorbs with the decrease of impedance and increase of corrosion current density while the inhibiting effect of EDTA-4Na enhances and the corrosion current density of the steel bars drops.The corrosion resistance of DMEA is stable and the steel bars are remained in passivation state all the time when MCI concentration and pH drop,but EDTA-4Na cannot provide stable corrosion resistance and the steel bars are in depassivation state most of the time.