Fabrication of Ag/AgCl electrode for detection of electric field in marine environment

Abstract

Underwater Electric Potential (UEP) and Extra Low Frequency Electric field (ELFE) measurement is very important and essential for defence and civilian applications. UEP signature is produced by an underwater vessel by corrosion currents in the ship or submarine hull and also from propeller or other dissimilar metallic material in contact with the salt / sea water. The hull of the ship and the propulsion also produces a modulation of the corrosion currents, which is called the ELFE signature. The underwater electric field detection is very important to find the presence or proximity of alien, or enemy underwater targets and their positioning by non-acoustic methods, in the defence sector. The electric field in the marine environment is measured usually with sensor electrodes that are either carbon fibre or silver/silver chloride (Ag/AgCl) based. The typical sensor system uses six electrodes, mounted on three orthogonal axes. By measuring the potential the potential difference between each pair of electrode, the electric field magnitude and the direction of source can be determined. In this study, Ag/AgCl electrodes have been fabricated by two different methods, thermal and thermal-electrolytic for the purpose of detection of marine electric field. Ag/AgCl electrodes, being reversible electrochemical electrodes, are ideal for measurement of marine electric field. Ag/AgCl electrodes have excellent electrochemical characteristics, such as very high ion exchange reaction current and lack of polarization at a low current density. The fabricated electrodes have been subjected to anodization by two different methods at constant potential and constant current, to increase the concentration of chloride ions for achieving fast equilibrium with chloride ions in sea water. The anodization process at constant potential is found comparatively more suitable in the study as it reduces the electrochemical noise associated with the electrode, the results of which are discussed. The electric field has been simulated in a tank and the characteristics of the fabricated electrodes are studied.