Measurements on Corrosion Rate of Reinforcing Steel under various Environmental Conditions, Using an Insulator to Delimit the Polarized Area

Abstract

This paper presents measurements of corrosion rate of reinforcement by means of the original method involving delimitation of the polarized area with an insulator. This method consists of a typical potentiostat connected with a three-electrode setup, in which a circular electrode used as the auxiliary electrode is placed on the surface of concrete, and the polarized area is delimited by making a notch along the whole thickness of concrete cover. The notch, finally filled up with resin, is ring-shaped with a diameter slightly larger than the diameter of the counter electrode. The results of this method were verified by conducting measurements in an aqueous extract from crushed concrete, with LPR and EIS methods. Its properties were modified to map various environmental conditions, e.g. strongly carbonated concrete, concrete saturated with chlorides, or concrete with satisfactory protective properties to reinforcement. Each of three extracts contained a polished rebar, and auxiliary electrodes – circular and rectangular (with its side length equal to rebar length) in shape. A ring insulator was modelled with a fragment of the plastic tube. The comparative analysis of results obtained for partial polarization process by a circular electrode, with and without the insulator impact; and for the complete polarization by a counter electrode, revealed effectiveness of the proposed method under various environmental conditions. Electrical simulation was used to explain the effect of delimiting polarized area of rebar.