1283. GULBRANSEN, E. A. Transition-State Theory of the Formation of Thin Oxide Films on Metals. Trans. Electrochem. Soc., vol. 83, 1943, 13 pp.; Chem. Abs., vol. 37, 1943, p. 2251. Transition-state theory of diffusion was applied to the rate of oxidation of metals as a function of temperature. The expression involves an entropy of activation as well as the energy of activation. Experimental results indicate that the oxidation of Fe, stainless steel, and Cu follows the parabolic law for certain temperature ranges and pressure ranges after a certain initial period. The parabolic-rate-law constants are shown to follow a straight line when log K is plotted against 1/T. Energies of activation of 22,600, 29,600 and 24,900 are found for Fe, stainless steel, and Cu, respectively. Entropies of activation are calculated to be -–1, -35, and –6.8 for Fe, stainless steel, and Cu, respectively. The importance of entropy factor is briefly considered. |