Detection of SCC on prestressing steel wire by the simultaneous use of electrochemical noise and acoustic emission measurements

Abstract Electrochemical voltage and current noise were measured simultaneously with acoustic emission (AE) measurements during the stress-corrosion cracking (SCC) of prestressing steel wire. Elongation of the specimens was also measured. Constant load tests were performed on specimens made from prestressing steel with a diameter of 3.2 mm: the central wire of a seven-wire strand was used. The specimens were exposed to diluted sodium thiocyanate (a modified version of the test as proposed in EN ISO 15630–3), with and without the addition of an organic corrosion inhibitor. EN was measured between the stressed central cold-drawn wire and the neighbouring wires which acted as reference electrodes for the electrochemical current and voltage measurements. AE was measured by two AE sensors fixed to the specimen. In order to characterize the SCC processes on the prestressing steel wire, the results of all the used techniques were analysed and compared. The effect of the inhibitor on these processes was also studied. A significantly longer time to failure was observed in the experiments with the added inhibitor. The results of the techniques, in combination with SEM and metallographic inspections, confirmed that the inhibitor had a specific influence on SCC. It was concluded that measurements of combined methods are promising for the reliable detection of SCC.