A physicomathematical model of corrosion of iron in a lead melt with an admixture of oxygen

Abstract

We propose a physicomathematical model for the corrosion of iron in a lead melt which contains oxygen. The model allows one do describe the distinct features and regularities of the kinetics of corrosion processes taking into account the multiphase and multicomponent nature of the system and the interaction of components during the processes of adsorption and diffusion. To adequately describe the phenomena under study when formulating the diffusion boundary-value problem, we used nonstationary conditions, which represent correlation surface physicochemical effects, for mass transfer through the interface.Liquid metal corrosion consists mainly in the dissolution of the components of a solid alloy in a liquid metal either in monatomic state [1] or in the form of complex compounds with nonmetallic admixtures (O, N, C) dissolved in the melt [2,3]. In other words, we have the flow of components of the alloy through the interface and their further diffusion into the melt in the monatomic or ionic state under conditions of thermal or concentration mass transfer.With high aCtivity of the nonmetallic admixture, however, its flow to the hard metal-liquid interface can be more intense than the counterflow of ions of the dissolved metal. In this case, the admixture dissolves in the solid metal [4,5], and a new phase forms and grows on its surface due to the interaction of the solid and liquid phases [6][7][8][9]. This can be a binary compound (oxide, nitride, or carbide) which, under certain conditions of the tests, inhibits corrosion processes, or this can be a complex ternary compound with a liquid metal component (MexNayOz, MexLiyN z, etc.) which usually favors the penetration of a melt to the solid metal matrix. The physical and mathematical models, which give a good description for various kinds of dissolution of a metal in the liquid phase, fully ignore the process of phase formation on the surface of the solid and its influence on the kinetics of corrosion [2, 10-13].The aim of this work is to develop, using the Fe-Pb-O system as an example, a physicomathematical model for adequate analysis of physicochemical processes in the zone of contact of the solid metal with the liquid one in a wide range of concentrations of the admixture in the medium. From the analytical point of view, the description of the phenomena is based on reactive diffusion and involves adsorption, chemical transformations, and diffusion of all components of the system. Physicochemical Aspects of the Interaction of Iron with a Lead MeltIf the medium (Pb) does not contain oxygen, then we have the dissolution of iron in lead [13,14]. In the opposite case, the atoms of oxygen are adsorbed on the surface of iron. Their surface concentration increases up to a value which corresponds to conditions of equilibrium with the medium. When it is insufficient for the formation of stable chemical compounds, then oxygen can dissolve in iron according to the law of diffusion. Simultaneously, iron dissolves in lead. But we have a more interesting case (from both the ...

Analysis on liquid metal corrosion–oxidation interactions

“…Matychak et al [18][19][20][21] developed a kinetic model for the Fe [Cr]-Pb-O system. The non-stationary boundary condition on the surface of mass transfer due to species diffusion was considered and formulated, while hydrodynamics was omitted.…”