KINETIC-BEHAVIOR OF PASSIVATION OF AN IRON ELECTRODE ON CHANGING FROM AQUEOUS TO AQUEOUS-DIMETHYLFORMAMIDE MEDIAстатья
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Дата последнего поиска статьи во внешних источниках: 29 мая 2015 г.
Аннотация:Electrochemical methods and ellipsometry have been used to study growth kinetics of oxide films on passive Fe in potentiostatic conditions on replacing an aqueous borate buffer solution by dimethylformamide (DMFA) mixtures with the same salt composition and, vice versa, replacing aqueous-DMFA mixtures by aqueous solution. Film growth in aqueous solution is described by a direct logarithmic law L approximately log t, where L is the film thickness and t is time, and on replacing the aqueous solution by an aqueous-DMFA mixture growth in L is retarded and there is a gradual transition (with increase in the proportion of DMFA in the mixture) to a parabolic law L approximately t0.5. Changing from an aqueous solution to aqueous DMFA favors increase in the adsorbability of anions and promotes pitting formation by the action of Cl- ions. The observed phenomena are explained on the basis of a model according to which the passivating film is a crystalline oxide with a large number of point defects (vacancies).