Polarization Behaviour of Silver in Model Solutions

Abstract

When studying chloride-induced corrosion in reinforced concrete structures, essential information of interest is the concentration of chloride ions in the system. The absence of a reliable method for monitoring the free chloride ions justifies the attempts towards establishing a feasible practice in the application of the already known Ag/AgCl electrode, as a chloride sensor. To identify the governing mechanism and cognition of causes for instability of the chloride sensors in highly alkaline medium (as concrete), it is necessary to study the polarization behaviour of silver in different aqueous solutions resembling the concrete environment. Following expectations and well-known fundamental background, the results from this work confirm that in the presence of chloride ions, silver chloride is the predominant reaction product, forming on the silver surface. Whereas, in the absence of chloride ions and/or presence of interfering ions, such as hydroxide ions, the oxidation process of AgCl formation is significantly dependent on the chloride concentration in the medium. Therefore, the formation of a stable AgCl layer on a Ag substrate (as would be required for sensors application for example) is a function of the presence and amount of interfering ions, together with the chloride concentration in the medium.