Anodic Dissolution of Beryllium in Anhydrous Media
Résumé
When the residual water content of currently used electropolishing solution is reduced to less than 0.1 g/1, the anodic dissolution of beryllium follows Faraday's law with a valence of one over an extended range of anodic potentials. This result is interpreted in terms of a dissolution mechanism occurring in a succession of two individual steps, each involving a simple electron, thus
Support for the transitory existence of the monovalent ions is derived from thermodynamic considerations allied with the structure of the anodic layer. Microscopic examination of the state of the anode surface during and after the dissolution shows clearly that a mechanical disintegration of the metal lattice by the action of the current cannot be the origin of the anomalous valence observed. On the contrary, it is shown that disintegration of this type contributes only at low anodic potentials. This phenomenon, known as the "chunk effect," is clearly observable by scanning electron microscopy and accounts for faradaic "efficiencies" of greater than 200% in certain electrolytic conditions.