NEW APPROACH TO THE KINETIC MODELLING OF HIGH TEMPERATURE CORROSION OF METALS AND ALLOYS

摘要

In this paper we present a new approach for the kinetic modelling of thermal transformations of solids. In the case of the corrosion of metals and alloys, the existence of a rate-limiting step is often assumed, which allows to account for the linear and parabolic kinetic curves (weight gain versus time), corresponding respectively to an interface and diffusion controlling step. But, in many cases, the reaction system is not so simple, thus we have developed a methodology in order to verify experimentally whether the kinetic assumptions of steady state and rate-limiting step can be applied. This is illustrated with two examples, leading to complex kinetic curves : the oxidation by oxygen of an Al-Mg5% alloy in the liquid state (non reproducible curves), and the oxidation of Zircaloy-4 by water vapour (existence of a kinetic transition).