关键词: 钢筋, 混凝土, 阻抗, 氯离子, 腐蚀

Abstract: Electrochemical impedance spectroscopy(EIS) was employed to study the influence of chloride on the corrosion behavior of reinforcing steel in concrete.In Nyquist plot,the spectrum consists of two semicircles,indicating that the reinforced concrete system contained two time constants,one derived from electrical double layer of reinforcing steel and the other from the deposition film of concrete layer.The depressed semicircle in lower frequency featured the non_faradic behavior of the electrical double layer (EDL) deviated from idea capacitor due to diffusive effect which was attributed to the surface roughness of rebar and the inhomogenity of concrete layer.Then the EDL was denoted by a constant phase element (CPE) other than a capacitor in the equivalent circuit.At the late stage of immersion,a new element,Warburg resistance W evolved along with dramatic decrease in the value of polarization resistance,Rp,convincing the break down of the passive film and the initiation of active corrosion.The increase of [Cl-] in external solution prominently accelerated this trend.