Advancements in non-destructive control of efficiency of electrochemical repair techniques

Abstract

The main electrochemical techniques used for reducing corrosion on reinforced structures are cathodic protection (CP), electrochemical chloride extraction (ECE) and realkalisation (ER). Traditionally, for controlling the efficiency of CP, standard methods based in the depolarisation of rebar are used, with inconvenience of requiring the interruption of the protection current even for several hours. Concerning ECE and ER, the usual methods involve extraction and chemical analysis (chloride and hydroxyl ions respectively) of cores from the structure. In this paper, some non-destructive methods for monitoring the performance of the electrochemical repair techniques, are presented and analysed. In CP, a new developed methodology, called passivity verification technique (PVT), which uses the electrochemical impedance spectroscopy concept, is described. This is a fast method that does not require interruption of the cathodic protection current and the results obtained are in agreement with those obtained by standard depolarisation methods. As long as ECE and ER are concerned, the corrosion potential and corrosion rate measured by the polarisation resistance technique are the suggested non-destructive indicators of the efficiency of the technique at the end of the treatment. Additionally, for ER, the detection of a sudden increase in the intensity of electrical current passing, and a parallel establishment of electro-osmotic flux, is also postulated as a key parameter for practical control during the application of the efficiency of the realkalisation. Finally, it is also presented a new parameter ‘standardised by the resistance charges (SRC)’, which would be a more indicative parameter than simple recording the coulombs to check the efficiency during ECE treatment.