Kinetic of electroformation of passive film on zirconium base alloys in halide aqueous solution by means of potentio-dynamic techniques

The potentio-dynamic technique has been used for investigation of the breakdown of the protecting oxide film on the surface of zirconium base alloys, under the influence of halide anions. For chloride and bromide solutions, only slight influence has been shown of these anions on the overall reaction mechanism associated with this process. However, the pitting potential depends on concentration of these anions which implies that they can be occluded during the growth of the oxide film. Two distinguishable contributions are found in iodide solutions. The one at a more negative potential is related with the active dissolution of the alloy, the other, with oxide film electroformation. The absorbability characteristic of I- ions must be considered in formulating an overall reaction mechanism for the passivity of zirconium base alloys