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The reduction of oxygen on film-covered zirconium was investigated by the measurement of the rate as a function of potentiai and concentration. The amount of hydrogen peroxide produced was measured and compared to the theoretical amount. The results showed two distinct polari zation regions, a very low- current region with a Trafel slop of about 1.4 (2.3 RT/F) and an oxygen order of unity, and a higher current region with a much larger Tafel slope and a fractional oxygen order. Equations accounting for the general features of the data are derived based on a model that considers the separate potential drops across the film and the solution double iayer. (auth)

The dissolution of crystal-bar zirconium in aqueous solutions containing HF and H2SO4 was investigated by means of electrochemical techniques. Capacities were determined by measuring the initial slope of the voltagetime curve resulting from the application of galvanostatic pulses. Steady-state polarization curves were obtained potentiostatically whenever possible, and galvanostatic polarization curves were determined by a pulse technique. The data are explained by assuming that the dissolution reaction involves the continuous formation and dissolution of a film on the surface of the metal. The conventional anodizing equation describes the formation of the film and the dissolution reaction is controlled by the rate of mass transfer of undissociated HF to the surface of the film.

Using an electrochemical method, rates of film growth in oxygenated sodium sulfate solutions have been measured on Polycrystalline zirconium at temperatures ranging from 25 to 88 deg C. The resulting rate-time plots are roughly hyperbilic. A model is proposed which when treated by electrode kinetics is shown to give this type of behavior. (auth)

Measurements were made of the rates of reduction of various oxidizing agents on passive zirconium in acid solutions of scdium sulfate at temperatures ranging from 25 to 85 deg C. The oxidizing agents were oxygen hydrogen ions, and cupric ions and hydrogen peroxide in the presence of oxygen. The kinetic orders of reduction were determined from potentiostatic experiments in which the current was determined as a function of concentration. Unit and fractional orders were observed with oxygen reduction, and fractional orders from about 0.5 to 0.65 were observed for Cu/sup ++/ and H/sub 2/O/sup 2/. Possible mechanisms are suggested in which charge transfer through the film is assumed to play a predominant role. (auth)