The Electrochemical Polarization of Zirconium in Distilled Water

Abstract

The cathodic polarization curve for zirconium in air saturated distilled water at 40 0 C. was determined in the current density range 3.0 x 10-7 to 1.0 x 10-3 amp./cm. 2. At low current densities the reaction was the reduction of dissolved molecular oxygen to hydroxyl ions, its limiting diffusion current being about 5 x 10-6 amp. /cm. 7. The formation of a zirconium hydride film was the reaction proposed to explain a plateau in the curve which had a constant potential of-0.30 volts vs. S. C. E. and a limiting current of 1. 0 x 10-4 amp. /cm. 2. X-ray diffraction data, time-potential curves, observations and other evidences substantiated this possibility. Above 1. 0 x 10-4 amp. /cm. 2 hydrogen evolution occurred and the curve followed a Tafel relationship, the slope being-0. 14 volts. The hydrogen overvoltage at 1. 0 ma. /cm. 2 was 0. 75 volts. The open circuit potential of zirconium in air saturated distilled water at 40 0 C. was determined to be +0.16 volts vs. S. C, E.