The Diffusion of Gases Through Metals from a Chemical Point of View

Abstract

The diffusion of gases through metals is considered from the point of view of chemical compounds between the metal or a constituent of it and the gas, all at chemical equilibrium. Without reference to the surface conditions the usual laws of diffusion are derived, and Fick's linear diffusion law is shown to be a consequence of the hypothesis. Cases are treated where one compound between the gas and metal is formed, where two compounds are formed, where one compound is formed between the metal and gas and another formed between an alloying agent and the gas, and where the same compound is formed but the metal has a transition between two forms. The theory correlates the magnitude of the exponent of the gas pressure in the diffusion isotherms with the chemical reactions within the metal. It also leads to certain consequences in regard to the magnitude of the diffusion and the energy of activation.