Abstract
A comprehensive first principles understanding of the oxidation of zirconium alloys by water was reiterated. Two channels were taken to jointly constitute to the oxidation process: one according to classical oxidation theory involving hydrogen evolution and the second reflected by inwards transport of protons causing hydrogen pick-up. The two were associated with charged and uncharged oxygen vacancies, respectively. The purpose of the present study was to clarify the nature of the effective anode during oxidation of zirconium as to the detailed role of the metal. Oxygen dissolution in the alloy resulted in a “pre-anodic” property associated with the formation of oxygen vacancy VO in the oxide, i.e., preceding VO2+/2e− separation. Atomistic perspective on the metal/oxide interface before nucleation of VO was provided. The rapid convergence of the model interface to bulk properties in spite of the local structural variability provided new insight as to the nature of an amorphous metal/oxide interface.
Highlights
The rate of any chemical reaction involving two and more reactants relies on their encountering
Oxygen dissolution in the alloy resulted in a ‘‘pre-anodic’’ property associated with the formation of oxygen vacancy VO in the oxide, i.e., preceding VO2?/2e- separation
While the driving force for the corrosion process reflects a generic thickness dependence of the chemical potential gradient, the rate of the oxide growth is determined in addition by the mobility of reactants through the barrier oxide
Summary
The rate of any chemical reaction involving two and more reactants relies on their encountering. The very build-up of reaction product at this interface complicates further encounter between reactants. The increasing impacts of the said competing processes are heralded by the ideal parabolic or sub-parabolic growth of the barrier oxide itself. This is because of the slow-down in the rate of growth owing to a decreasing chemical potential gradient. While the driving force for the corrosion process reflects a generic thickness dependence of the chemical potential gradient, the rate of the oxide growth is determined in addition by the mobility of reactants through the barrier oxide
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