Effect of heat treatment on the periodic current oscillation of polycrystalline zinc in alkaline solution

Abstract

The phenomenology of the periodic oscillations of the faradaic current of zinc electrodes in alkaline solutions offers the possibility of investigating the influence of the non-uniformity of the polycrystalline metal surface on the periodic effect because the grain size of zinc can be easily controlled by the annealing temperature and time. Zinc rods (0.6 cm dia., Leico 99.999% purity) were annealed at 390°C during a period of between 2 and 6 h and cooled down for about 18 h. Each annealed rod was axially embedded in a PTFE rod to make a still zinc disc working electrode in contact with 1.5 M NaOH at 25°C. Other experimental details are as described in a previous publication. The morphology of the attack of the different electrode surfaces is shown in Fig. 1. From these pictures the surface density of grains at the electrode was calculated.