Investigation into the oxidation of zirconium and its alloys by the electrochemical parameters in various media

The behaviour of zirconium and its alloys with aluminium, chromium, hafnium, molybdenum and niobium has been studied during heating and annealing in oxygen and argon. The studies have included registering the oxide film thickness, measuring the electromotive force and the shunting current value. The effect of alloying elements on the processes occurring in the system metal-oxide film has been studied during oxidation in oxygen and annealing in argon. It is found that the value of the shunting current during the oxidation of metals is determined by the relationship between the ionic and electronic resistances of the oxide film and this value can be used for estimating both these resistances and the oxidation rate, when the metal-oxide film system is affected by various factors. When annealing in argon the pre-oxidized samples of zirconium and its alloys, the ionic resistance of the oxide film decreases, which results, in the consecutive oxidation in oxygen, in a considerable increase of the shunting and corrosive current. It is found that chromium and molybdenum delay the cathode reaction, whereas hafnium, niobium and aluminium accelerate it