الکترود نظارت خوردگی درجای جدید برای سازه های بتن آرمه A novel in-situ corrosion monitoring electrode for reinforced concrete structures

1. Introduction Reinforced concrete is protected by a thin passive film formed on the surface of the steel rebar. The high alkaline environment of the concrete pore solution enables the formation of the protective oxide film on the steel rebar surface which delays the initiation of corrosion [1]. However, the passive films get disrupted due to the ingress of chloride ions and initiate the corrosion of the embedded steel rebar with prolonged time of exposure [2]. Reinforced concrete structures, when exposed to severe marine environments, leads to the premature failure of the concrete structures [3,4]. Premature failure of the structures is minimized, and the durability of the concrete structures are enhanced by the continuous and periodical health monitoring of the concrete structures [5,6]. Health monitoring techniques include, destructive (core drilling and chloride extraction) and nondestructive techniques [7-14], electrochemical methods such as electrochemical impedance, electrochemical noise, galvanostatic pulse, linear polarization resistance, half-cell potential measurements and embeddable corrosion monitoring sensors [15-21] have been widely used to measure the corrosion of the reinforcing steel rebars in concrete. Among these methods, embeddable solid-state sensors are the most reliable technique and simply adaptable method which would be used in the field conditions for measuring the corrosion status of the steel rebar [22]. Studies revealed that solid state sensors could able to provide more reliable and accurate status of the steel rebars (active or passive) due to the minimized IR drop, maintenance free and can be used for long-term corrosion monitoring application of reinforced concrete structures [23-28]. The in-situ durability parameters such as corrosion rate, resistivity, temperature, crack, deformation humidity, pH of the important concrete structures, bridges and other infrastructures which are located very close to the marine environments could monitor through embeddable sensors. Based on the complete information on the condition of the structure, effective control measures may be taken in advance, and the stability of the structure can be maintained [29- 37]. The Ti and Ag/AgCl electrode have been used for pH and Clion concentration monitoring in concrete [38-41]. Surface mounted glass electrodes are not suitable for in-situ measurements [39] because the high resistance of the cover concrete and the dryness of the concrete will affect the conductivity of the measurements and will not able to provide the accurate results when embedded in the concrete [42].