Electrochemical passivation studies of zircaloy in presence of metal ion

Inorganic metal ion additives are being explored for controlling the corrosion and deposition of activated corrosion products on out of core surfaces in Pressurized Heavy Water Reactors. Addition of Mg⁺² to the process stream is reported to be beneficial in reducing corrosion and corrosion product release from carbon steel. This added Mg⁺² ions can modify the oxides on other heat transfer surfaces and thus influence their corrosion behavior. In this context, an attempt was made to study the role of Mg⁺² ions in modifying the passive films on Zircaloy surfaces by electrochemical passivation at ambient temperatures. Increased polarization resistance obtained from the impedance spectra recorded at OCP in the presence of Mg⁺² ions revealed the beneficial effect of Magnesium. Different potentials were identified from the the polarization curves. Each potential was applied to the specimen surface and the film growth was monitored by amperometry as well as by obtaining time evolution impedance spectra. The results obtained from the above studies are discussed in detail in this paper. (author)