β Scribed by G.S. Bell
No coin nor oath required. For personal study only.
A s ummary of the present state of knowledge is given regarding the various parameters &flue&q the rate of corrosion of zinc anodes in ZnCl,/NH,Cl electrolytes. These factors include zinc composition and grain structure, the use of inhibitors and the influence of soluble impurities in the electrolyte.. R&urn&Les cormaissances actuelles sur la corrosion du zinc dans des solutions de Z&IS-NH&X sent resum&s. On 6tude l'influence des facteurs suivants: composition et texture du zinc, emploi d'inhibiteurs et presence d'impretb solubles dans 1'6lectrolyte. Zusamme&ssung-Die heutigen Ken&&se auf dem Gebiet der Korrosion von Zinkelektroden in Z&l-NH&l-Elektrolyten werden zusammengefal3t dargestellt. Dabei werden folgende Elnflu& griiDen untersucht: Zusamm ensetzung und Komstruktur der Zinklegierung, die Verwendung von Inhibitoren und schli&lich der EinfluO von l&lichen Verunreinigungen im Elektrolyten.
IT IS well known that although zinc is thermodynamically unstable in aqueous solutions, the rate of corrosion is dependent on several factors, which have been investigated during the last 50 years. We first consider the present state of the art and establish how far anodic corrosion represents a limiting feature in the quality of commercially available dry cells.
If we take a metal-clad, pasted type "D" size cell as typical, experience teaches that reasonable performance after 5 years storage at 20" is by no means unusual, although the reliability may not be all that could be desired. For cells of other dimensions, capacity retention after storage is more or less proportional to the cell volume, smaller cells being less and larger cells more stable.
In order to achieve this result manufacturers have evolved rigid systems of rawmaterial and process control. We fist examine analytical results obtained from the products of prominent manufacturers. Table 1 shows individual analytical resultsthe figures cannot be interpreted as averages-obtained in our laboratories during routine examination of competitive products.
In addition to the specification of the zinc composition various corrosion inhibitors are employed. Mercury is in general use in amounts usually between 0.02 and O-1 per cent of the total anode weight. Mercury is however seldom used alone. The cereals used in the electrolyte paste also have inhibiting properties. Chromate is also widely recognized as a corrosion inhibitor, although its application in practice is somewhat limited. Several organic compounds also have been recommended, in particular substances capable of forming complexes with ions known to accelerate anodic corrosion.
The careful choice of the zinc composition and the application of effective corrosion inhibitors must be supported by stringent control of the remaining raw materials and * Presented at the colloquium of CITCE,
π SIMILAR VOLUMES
The dc conductivity (Ο) along the polar b-axis of ammonium zinc chloride (AZC) crystals in its four hightemperature phases has been measured as a function of temperature. Doping with Mn 2+ in different concentrations changed strongly both values of Ο at all temperatures and the dependence of ln Ο dc
The spectral characteristics of aqueous zinc chloride solutions (67% w/w) containing cellulose, cellobiose, maltose, β€-methyl glucoside, and glucose were compared. The results suggest that zinc ion forms loose complexes with the C2 or C3 hydroxyl groups of glucose or methyl glucopyranoside. The abso