应力作用下钢筋在模拟混凝土孔隙液中的钝化行为研究

Passivation Behavior of Steel Bar Subjected to Tensile Stress in Simulated Concrete Pore Solution

本文针对应力作用下模拟混凝土孔隙液环境中钢筋钝化行为开展了研究。通过电化学测试技术(电位、线性极化电阻、循环伏安曲线、电化学阻抗谱、电化学噪声)对钢筋在持续拉应力作用下的钝化行为进行了分析;采用X射线光电子能谱技术(XPS)表征了不同应力作用下钢筋表面的钝化膜。结果表明,拉应力显著增大了钢筋钝化过程氧化还原反应的活性,且拉应力水平越大氧化还原反应的活性越高。然而随着拉应力的增大,钝化膜中Fe^(2+)/Fe^(3+)比值增大,钝化膜稳定性下降。由此,拉应力作用特别是较高应力水平(超过60%屈服强度)显著降低了钢筋的钝化膜电阻、噪声电阻、极化电阻,增大了其在钝化状态时的电流密度。

The present study aims to investigate the passivation behavior of steel bar subjected to tensile stress in a simulated concrete pore solution(SCPS).The passivation behavior of the stressed steel was studied by electrochemical techniques including open circuit potential,linear polarization resistance,cyclic voltammetry,electrochemical impedance spectroscopy and electrochemical noise measurement.The passive film of the stressed steel was characterized by XPS.Results indicated that the applied tensile stress enhanced the redox activity in highly alkaline SCPS,where the enhancement was proportional to the level of tensile stress.Nevertheless,the increment of tensile stress led to passive film with a higher value of Fe^(2+)/Fe^(3+)and therefore a poorer protectiveness.As such,tensile stress especially high stress level of tension(over 60%yield strength)significantly reduced the resistance of passive film,the noise resistance,as well as the polarization resistance,leading to a higher value of current density of the passive steel.