混凝土养护期间HRB400钢筋钝化行为研究

为了研究HRB400钢筋在模拟养护阶段混凝土孔隙液中表面钝化膜的生长过程，采用3种电化学测试技术(开路电位、电化学阻抗谱、动电位极化曲线)研究钢筋表面钝化膜的性能随着浸泡时间的变化特征，此外通过XPS对稳定钝化膜的成分与结构进行分析。结果表明，同传统钢筋材料一样，HRB400钢筋在模拟混凝土养护条件的溶液中展现出良好的耐蚀性能，浸泡5 d后便能够生成稳定钝化膜。XPS分析发现钢筋钝化膜为双层结构，内层以二价铁离子化合物为主，外层主要由三价铁离子化合物组成。

Characterisation of Passive Film on HRB400 Steel Rebar in Curing Stage of Concrete

The standard curing time of concrete is 28 days in order to guarantee the strength of the concrete. It is well known that a stable passive film can be formed on the surface of steel rebar in the alkaline pore fluid during the concrete curing stage, long before the steel rebar will be influenced by chloride ingress or concrete carbonation in the future. However, there is no consensus on the time conditions for the pre-passivation of the steel bars in the open literature. In this study, the growth process and characteristic evolution of the passive film formed on HRB400 steel rebar in a Ca(OH)₂ saturated solution, which aims to simulate the medium in concrete pores during curing period, were studied by a series of electrochemical tests (open-circle potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve (PDC)) and XPS. Results show that it will take 5 days to form a stable passive film on the surface of HRB400 steel rebar, and the passive film has a two-layered structure. In the initial stage of passivation, on the HRB400 steel surface a thin film mainly composed of Fe(II) products firstly formed, then on top of which, a film mainly composed of Fe(III) products would further form.