The Influence of Electrolytes on the Mechanical Properties of Certain Metal Single Crystals

Abstract

The contact of electrolytes has a marked effect on the mechanical behaviour of single crystals of cadmium and zinc which have been exposed to the air This is due to the disruption, or formation, of a thin surface film, probably of oxide or hydroxide. If ordinary single crystal cadmium wires are loaded so as to flow very slowly, the contact of solutions containing free cadmium ions increases the rate of flow a similar effect exists in the case of zinc treated with solutions of zinc salts If the surface of the wire is cleaned by preliminary thermal evaporation there is no such effect, establishing that it is due to a surface film normally present. Solutions of cadmium or zinc nitrate stop the flow and raise the critical shear stress appreciably, which is attributed to the formation of a surface film, probably of hydroxide With the cadmium nitrate there is a temporary increase of flow before the cessation, which is attributed to the cadmium ion, for there is no such effect with the zinc nitrate With polycrystalline wires there is no electrolyte effect The work described supports the view that a thin oxide or hydroxide film increases the mechanical resistance of single crystal wires, and that with cadmium and zinc wires such a film is normally present.