Platinum Metals Review - Volume 27, Issue 1, 1983

Over the past quarter of a century a combination of platinum and titanium has been used increasingly as an electrode material for the cathodic protection of steel in marine environments and underground structures. As a result of accumulated experience gained in many situations it is now possible to set guidelines within which the material may be used with confidence, thus greater application is probable.

Recent advances in brightener chemistry have made it possible to electrodeposit microcrack-free, (111) oriented palladium of very high brightness and lustre. This preferred crystallographic orientation results in a major improvement in resistance to wear, still further increasing the attractiveness of palladium as a replacement for electrodeposited gold.

The oxidation behaviour of platinum and its alloys at high temperatures is of fundamental importance to its application as both a structural material and a catalyst in a wide range of industrial processes. One of the principal factors determining the efficiency of a catalyst is its surface condition and this in turn depends upon both the initial surface preparation and the changes in surface structure and composition that take place during use. During the manufacture of nitric acid from ammonia a rhodium-platinum catalyst gauze is employed, and under the reaction conditions the surface of the catalyst is altered. The processes involved in this change are not yet fully known, but a study undertaken to provide a more detailed characterisation of the oxide layer formed upon the surface of rhodium-platinum is now reported and may have relevance both to its use as a catalyst in ammonia oxidation and as a structural material.

Since the discovery by Davy in 1817 of catalytic oxidation on the surface of platinum there has been much discussion of the underlying reasons for the occurrence of heterogeneous catalysis. Early ideas of Liebig found little favour with Berzelius, Ostwald and others. The adsorption theory of Faraday became generally accepted, although alternative views were proposed over a long period. Langmuir put the concepts of Faraday into definite form, and his formulations and developments of them have been used up to the present.