Corrosion monitoring based on diffuse ultrasonic CWI technique applied to infrastructures in contact with sea water: case study

The present study has been conducted in the frame of Interreg SOCORRO2 (Seeking out corrosion - before it is too late) project which aims to provide industries with an independent tool to assess corrosion risks of their installations in contact with sea water. The implementation of such a tool would increase their awareness and would allow them to take appropriate preventive actions against corrosion damage that often results in economic losses. Therefore, we investigated a non-invasive ultrasonic method to detect and follow chemically and microbiologically induced corrosion using Coda Wave Interferometry (CWI) method. In this paper, CWI based on ultrasonic diffuse waves is applied, for corrosion assessment on two specimens: iron and stainless steels and in two distinguish configurations: pure water (served as reference state) and salt water (3% NaCl). Both structures are monitored using two embedded Ultrasonic transducers at 1 MHz. The correlation coefficient (CC) is computed for each coda-window according to the reference. Different corrosion cells and configurations (corroded material, electrolyte, free potential, imposed potential) were considered to validate the ability of the sensor to detect corrosion phenomena and describes different forms of corrosion: generalized corrosion, localised corrosion, oxidation, passivation. The present work presents the preliminary findings obtained by CWI and theirs correlation with the corrosion in steels.