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ZIRCONIUM Corrosion in hot water and steam. Metallic zirconium and its alloys have assumed much importance as construction and protection material in nuclear reactors cooled with water or heavy water. Among the properties favouring this application are low neutron absorption, favourable mechanical characteristics, and a high corrosion resistance to water and steam. This corrosion resistance can be further improved by using suitable zirconium alloys. Even so, there are still certain undesirable corrosion phenomena which cause trouble. These have been made the subject of further research, e.g. in the metal laboratory of the Metallgesellschaft A.G., Frankfurt‐am‐Main. In this connection, a distinction must be made between two phenomena which occur simultaneously but are, as far as it's known at present, basically independent of each other, viz. oxidation and hydrogen absorption. But the extent to which the hydrogen freed in the course of the oxidation process can be absorbed by the zirconium and thereby cause brittleness depends not only on the external conditions but also on the type and quantity of the alloying components. During oxidation, the slow formation of a thin, bluish oxide film is liable to be followed by a more rapid ‘breakaway’ corrosion process in which a white oxide is formed that will soon peel off. There is, as yet, no satisfactory theory which would appear to provide a full explanation of all the phenomena encountered. The author discusses the research methods, the corrosion phenomena as such, the influence of certain alloying constituents on these phenomena and the various attempts at interpreting them.—(H. W. Schleicher, Metalloberfläche, 1961, 15 (8), 234–240.)