The present contribution is intended to provide an in depth approximation to the role plaid by the thick passive layers formed over years in atmospheric exposure in the electrochemical response of steel embedded in concrete. This information is expected to be of general interest for the interpretation of electrochemical data as the corrosion potential and the polarization resistance, commonly employed for assessing steel corrosion in this system. Results for blank samples and samples containing chlorides are discussed based on findings from electrochemical impedance spectroscopy. Temperature was considered in the study as a parameter for acting on both the chemistry of the pore electrolyte and the specific volume of the oxides layer. By this approach, we were able to identify the contribution of the oxides layer to the impedance spectra in the 10 kHz-1 Hz frequency range. Kinetic information for corrosion rate can be obtained in the low frequency region of the impedance spectrum. The polarization resistance, the DC resistance value, has to be corrected for the impedance at about 1 Hz. The oxides layer supports the oxygen cathodic reaction, but also the anodic and cathodic processes corresponding to the re-oxidation and reduction of the layer itself. Compared to layers formed in the absence of chlorides, the presence of chlorides in the concrete mix leads to the formation of a more oxidised oxide layer, with decreased redox activity and more prone to cracking under thermal cycling. Thus, the presence of chlorides decreases the corrosion protective property of the oxide layer.

本贡献旨在提供深度近似，其显示了由多年形成的厚钝化层在大气中暴露于埋入混凝土中的钢的电化学响应中所扮演的角色。预期该信息对于解释电化学数据（腐蚀电位和极化电阻）具有普遍意义，通常用于评估该系统中的钢腐蚀。基于电化学阻抗谱的发现，讨论了空白样品和含氯化物样品的结果。在研究中，温度被认为是同时影响孔隙电解质的化学性质和氧化物层比容的参数。通过这种方法，我们能够确定氧化物层在10 kHz-1 Hz频率范围内对阻抗谱的贡献。可以在阻抗谱的低频区域获得腐蚀速率的动力学信息。极化电阻（直流电阻值）必须针对大约1 Hz的阻抗进行校正。氧化物层支持氧的阴极反应，但也支持与该层本身的再氧化和还原相对应的阳极和阴极过程。与没有氯化物形成的层相比，混凝土混合物中氯化物的存在会导致形成更多的氧化层，氧化还原活性降低，并且在热循环下更容易开裂。因此，氯化物的存在降低了氧化物层的腐蚀防护性能。