关键词: 钢筋, 混凝土, 电化学噪声, 电化学阻抗谱

Abstract: The corrosion behavior of reinforcing steel in concrete under dry-wet cycle condition has been studied by electrochemical noise(EN) compared with the electrochemical impedance spectroscopy(EIS),SEM micrographs and EDS.The statistical method has been employed to analyze the EN data of reinforcing steel in concrete,which revealed three different corrosion stages of reinforcing steel in concrete,including the dissolution of the passive film,the active corrosion and the cumulation of corrosion product.The wavelet transform has also been employed,which indicated that steel in concrete with pH 1 is associated with uniform corrosion,while steel in concrete with pH 3 and pH 7 are associated with localized corrosion,such as pitting corrosion.From the analysis of the shot noise theory,it was found that pitting corrosion is enhanced in pH 1 solution.Electrochemical impedance spectroscopy(EIS) also indicated that there were three corrosion stages of reinforcing steel in concrete.During the first stage,the spectrum consists of two capacitive loops,indicating that the reinforced concrete system contained two time constants.The first loop in the high frequency region was related to the capacitance and resistance of the concrete,while the second capacitive loop in the low frequency corresponding to the steel-concrete interface;during the second stage,there are three capacitive loops in the spectrum,the second capacitive loop in the intermediate frequency region should be ascribed to the rust layer of the steel;during the third stage,due to the diffusion of the corrosion product,the diameter of the semi-circles in the intermediate frequency region begins to decrease,especially in pH 1 system,it drops to very low value.

Key words: steel, concrete, electrochemical noise, electrochemical impedance spectroscopy