Determinação de parâmetros cinéticos de oxidação de metais

Abstract

The corrosion is a usual process present in metallic materials and, as a natural and spontaneous process, the corrosion brings several damages, since, when oxidated, the metals loses their properties and need be replaced. The deterioration of these kind materials is mainly caused by chemical or electrochemical interaction between the material and the corrosive environment. Thus, we attempted, in this work, to analyze the oxidation rate in several metals and its alloys such as: copper, zinc, galvanized steel, stainless steel 316 and stainless steel 405. The samples were oxidized on exposure to the atmospheric environment and in acidic and basic solutions, taking into account factors such the nature and concentration of the oxidant medium. It was observed that the samples exposed in the environment does not obtained significant variations, which may be due to little precipitation occurred in the exposure period, and the characteristics of the samples. To the samples exposed in both, acidic and alkaline solutions, it were observed that the reaction rate increases in proportion to the incensement of the oxidant concentration solution. It is completely coherent with the kinetic theories, where the reaction rates are directly proportional to the reagents concentration. Samples of galvanized steel and stainless steel, when immersed in highly concentrated acid solutions, presented high reaction speed, showing that this material should not be used in applications in aggressive environment, once the formed passive layer is destroyed by highly concentrated acid solutions, increasing the degradation rate of the material.