KOROZE SLITIN ZIRKONIA V PROSTØEDÍ VVER [Corrosion of Zr-alloys in WWER environment]

Abstract

The corrosion rate of zirconium alloys in VVER water is typically determined from non in-situ techniques (weight gain) that are not able to measure the instantaneous corrosion rate. This problem could be solved by using a combination of electrochemical impedance spectroscopy (EIS) and polarization measurement. We evaluated this combined approach for the in-situ determination of the corrosion rate of E110 and Zry-4 in VVER water (boric acid, potassium hydroxide, lithium hydroxide) at temperatures up to 340 °C. Impedance data were obtained over a wide range of frequencies and then approximated using the Rs(QoxRox)(QdlRp) model of equivalent circuit. The polarization resistance Rp and Tafel parameters obtained from polarization measurements were used to gain an instantaneous corrosion rate. The Tafel parameter for a cathodic reaction was 160 mV/dec, thus obtained the instantaneous corrosion rate was then converted into the cumulative corrosion rate applying a combination of Faraday’s law and Stern–Geary equation. The resulting cumulative corrosion rate was then correlated with cumulative corrosion rate obtained from weight gain measurements. Evaluated corrosion rates were consistent.