Various electrochemical methods for evaluation of corrosion of steel reinforcement in concrete have been studied and reviewed regarding applicability in the field. Laboratory experiments have been carried out with steel in synthetic pore water and i n concrete blocks with chloride additions. The field measurements were performed at a large concrete bridge on the coast. The methods examined are manual potential mapping, automatic measurements of the corrosion potential with embedded reference electrodes, potentiokinetic linear polarisation resistance (LPR) measurements with cut reinforcement bars, analysis of the shape of galvano static charging curves, and LPR measurements of
the reinforcement with a commercial instrument containing a guard ring.
The corrosion rates determined with the guard dectrode instrument were not in good agreement with estimates based on potential mapping and with result of visual inspection. Due to the high interfacial capacitance of the steel in concrete, potentiokinetic LPR measurements were found to be little suited for determination of the corrosion rate. Good experience was obtained by computer modelling of the galvanostatic charging curve with calculation of the polarisation resistance from this type of data. The important advantage cf this method is that it is little influenced by the
electrical resistance in the concrete and that unreliable measurements can be sorted out when the curves do not follow the theoretical pattern.
Keywords: Corrosion measurements, concrete, steel, polarisation resistance, electrochemistry, electrode potential.