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应用电化学噪声技术,结合电化学阻抗谱研究了干湿循环条件下3种不同pH值的3.5%NaCl溶液中混凝土钢筋的腐蚀过程.结果表明,钢筋的腐蚀分为3个阶段:钝化膜的溶解期、腐蚀活化期和腐蚀产物的累积期.在pH1的溶液中经过30个干湿循环后主要以均匀腐蚀为主,而对pH3和pH7溶液,则主要以点蚀为主,散粒噪声分析证实了混凝土中钢筋在强酸性溶液中更容易发生腐蚀.电化学阻抗谱分析也进一步说明了混凝土中钢筋的腐蚀经历了3个阶段:第1阶段Nyquist谱图中出现两个时间常数,高频区为混凝土层的容抗性质,低频区为钢筋与混凝土界面的电荷转移电阻;第2阶段,中频区增加一个时间常数,这与腐蚀产物的累积有关;第3阶段,随着腐蚀产物向混凝土中的扩散,中频区容抗弧有所减小,特别是pH1体系,中频弧几乎消失.SEM形貌表征观察到随着溶液酸度的增加钢筋表面的锈层明显增多.
Electrochemical noise technique was used in combination with electrochemical impedance spectroscopy to study the corrosion process of concrete rebar in 3.5% NaCl solution with three different pH values under wet-dry conditions.The results showed that the corrosion of rebar was divided into three stages: passive film Of the dissolution period, the corrosion activation period and the cumulative period of corrosion products in the pH1 solution after 30 wet and dry cycles mainly uniform corrosion, and pH3 and pH7 solution, the main pitting corrosion, particulate Noise analysis confirmed that steel reinforced concrete is more susceptible to corrosion in strong acidic solution.Electrochemical impedance spectroscopy analysis further demonstrates that steel corrosion in concrete goes through three stages: two time constants appear in the Nyquist spectrum of stage 1, The high frequency region is the capacitive reactance of the concrete layer and the low frequency region is the charge transfer resistance of the interface between the steel bar and the concrete. In the second stage, a time constant is added to the middle frequency region, which is related to the accumulation of corrosion products. In the third stage, In the case of diffusion to concrete, the arc resistance of medium frequency zone is reduced, especially in pH1 system, the arc of intermediate frequency almost disappears.SEM morphology characterization shows that the rust layer on steel surface increases obviously with the increase of solution acidity.