Radiochemische untersuchungen über die korrosion des zinks und den heterogenen isotopenaustauch zwischen zink und gelösten zinkionen

Abstract

The heterogeneous exchange of zinc ions between zinc plates and solutions was studied with the complete exclusion of oxygen. In the presence of oxygen the corrosion in different electrolytes was investigated. Plates of very pure zinc were used and 65Zn and 59Fe were used as tracers respectively. The investigations showed that no heterogeneous exchange took place under the experimental conditions (room temperature) within the error of the measurements. (<0·1 surface layers were engaged in the exchange reaction.) The phenomena which have been described in the literature as heterogeneous exchange were due to corrosion or adsorption. The corrosion was studied at the very early stages using autoradiography, at a time when corrosion products can be found neither by chemical nor by X-ray methods. The labelled ions are engaged in forming the corrosion products; 59Fe is engaged in forming the cathodic corrosion product only. Heterogeneous exchange with the corrosion products does not take place to a measurable amount. The different behaviour of zinc in NaCl, Na 2SO 4 and NaNO 3 solutions is explained essentially by the different properties of the hydroxy salts of zinc. Pitting was already observed in water after 1 to 2 hr. Lower corrosion rates and uniform distribution of activity was found in the presence of inhibitors; insufficient concentrations of inhibitors lead to pitting.