Abstract
Cathodic protection is a technique that has been used to control corrosion and increase the service life of reinforced concrete structure. Standards as EN ISO 12696 give protection criteria for both impressed current and sacrificial anodes techniques, based on potential value or decay during a depolarization sequence. The polarization (current ON) and depolarization (current OFF) is experimentally studied on a corroded concrete wall thanks to six references electrodes and compared to a time-dependent modelling using FEM software COMSOL Multiphysics. Both experimental and numerical results show significant differences in the time response according to electrode location. This conclusion indicates that the concept of protection criteria defined by the standards is not suitable to assess the efficiency of cathodic protection applied to reinforced concrete structure.
Highlights
Cathodic protection (CP) is a technique used to control the corrosion of a metal by making it work as a cathode in an electrochemical cell
According to the standard EN ISO 12696 (2016) [7], current densities to be applied for cathodic prevention range between 0.2 mA/m2 and 2 mA/m2 of steel reinforcement surface compared with a range of 2 mA/m2 to 20 mA/m2 of steel reinforcement for cathodic protection on existing structures [7]
The standard states that protection is ensured when one of the following three conditions is verified for the whole reinforcement: For any structure, any representative steel in concrete location shall meet any one of the criteria given a) b) c) a) An “Instant OFF” potential (EOFF) more negative than ‐720 mV with respect to Ag/AgCl/0.5 M KCl reference electrode; which corresponds to ‐680 mV /saturated calomel electrodes (SCE) (Saturated Calomel Electrode); b) A potential decay over a maximum period of 24h of at least 100 mV from EOFF; c) A potential decay over an extended period of at least 150 mV from EOFF subject to a continuing decay and the use of reference electrodes for the measurement extended beyond 24h
Summary
Cathodic protection (CP) is a technique used to control (prevent or avoid) the corrosion of a metal by making it work as a cathode in an electrochemical cell. According to the standard EN ISO 12696 (2016) [7], current densities to be applied for cathodic prevention range between 0.2 mA/m2 and 2 mA/m2 of steel reinforcement surface compared with a range of 2 mA/m2 to 20 mA/m2 of steel reinforcement for cathodic protection on existing structures [7]. In order to complete these results, this paper proposes a discussion based on an ICCP system applied to a reinforced concrete wall which is monitored in six different locations simultaneously using six references electrodes. A voltage of 5 V was maintained between the two solution containers, using MMO titanium electrodes, until chloride‐ induced corrosion initiated on embedded steel bars close to the chloride source. The 5 remaining channels are used only to collect potentials relative to the other electrodes
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