Antoshchak I. Determination of the electrochemical properties of the principal nuclear power plant steels in high-temperature aqueous media

The dissertation is devoted to the following issues: the development of the equipment and the methodology for the high-temperature electrochemical investigations of the corrosion processes; the determination of the basic high temperature parameters of the silver-(silver chloride)reference electrode; and the electrochemical investigations of the two steels, 15Kh2NMFA and 08Kh18N10T, in PWR boric water at temperatures from 25 to 300oC. It has been established that the surface of the electrode needs to be cleaned at the studied temperature. The temperature coefficient of the EMF of the silver-(silver chloride) electrode and the KCl activity coefficient as a function of concentration at different temperatures have been established. Under the studied conditions, the thermal liquid junction potential was found to be constant within the range of KCl concentrations from 0,01 to 1 mol/kg. Both, the repassivation kinetics of the freshly formed surface (FFS) of the two steels, 15Kh2NMFA and 08Kh18N10T, in PWR boric water and the chronoamperometric behavior of the galvanic couple (FFS)-(passive surface) have been investigated. The correlation between the temperature dependencies of current and potential of the couple (FFS)-(passive surface), and crack growth rate under corrosion fatigue conditions has been established. The mechanism of growth of the corrosion fatigue crack has been proposed.