Experimental set-up for electrochemical measurements in hydrothermal sub- and supercritical oxidation: polarization curves, determination of corrosion rates and evaluation of the degradability of reactors during hydrothermal treatments of aqueous wastes

Electrochemical data concerning metallic materials submitted to aqueous media at high pressures and high temperatures, which are close to the critical point, are scarce. This is essentially due to the difficulties encountered during the setting-up of an appropriate system of analysis. This paper, in the peculiar context of organic wastes supercritical water oxidation, proposes, for both sub and supercritical conditions, some technical solutions to define a cell able to give access to quantitative electrochemical information. For special media (pH≥1.7 and chloride ions content≈1 g/l), using a specific device consisted of a TA6V electrochemical cell, ensuring lasting and chemically inert electrical isolation and water tightness, along with a hydrogen dynamic electrode (HDE), it is possible to obtain reliable ‘current–potential’ curves allowing a quantitative exploitation, particularly for corrosion rates determination.