钢筋在模拟碳化渐变条件下的腐蚀过程研究

Corrosion of Reinforced Steel Bar in Simulated Pore Solution with Gradual Augment of Carbonation

采用电化学阻抗谱(EIS)和极化曲线研究了供货状态和打磨光滑钢筋在模拟孔隙液中碳化渐变条件下的腐蚀行为.采用扫描电镜结合能谱(SEM/EDX)和X射线衍射(XRD)对钢筋表面形貌和组成结构进行了分析.结果表明:碳化过程中钢筋表面的电化学行为可分为2个过程,即钝化膜形成或修复过程以及钙沉积过程.在混凝土碳化的过程中,并不是随着pH值降低随即就发生腐蚀,而是随着时间的进一步推移,当CaCO_3转化为Ca(HCO_3)_2,沉积层破坏时才发生腐蚀.另外,供货状态和打磨光滑钢筋在此过程中的响应时间有一定差异.

The corrosion behavior of with gradual decrement of pH value electron microscopy combined with reinforced steel with different surface state in simulated pore solution was investigated by using electrochemical measurement and scanning energy dispersive X-ray spectrum（SEM/EDX） and X-ray powder dif- fraction（XRD）. The changes of corrosion potential and corrosion current intensity of reinforced steel bar with gradual change of solution system were obtained, and morphology and structure of corrosion products formed in the sample were analyzed. The results show that the electrochemical behavior of steel surface is different in two processes of carbonation：the formation or restoration of passive film and the sedimentation of CaCO3. The corrosion of reinforced steel bar in the concrete does not occur immediately after the decrea- sing of pH value. Instead, the corrosion occurs when CaCO3 is transformed into Ca（HCO3）2, which means that the sedimentary layer is damaged. Furthermore, there are differences in the response time to corrosion between as-supplied state and polished state steel bar.