Abstract
IN 1790, James Keir1 discovered that treatment of iron with nitric acid produces a peculiar condition in which the metal loses its power of precipitating silver from silver nitrate, although retaining its ‘metallic splendour’. The behaviour of iron towards nitric acid was further examined by Schonbein2 and Faraday;3 Schonbein described the peculiar condition as ‘passivity’. Later work has shown that many other oxidising agents render iron passive towards reagents which attack the metal in its ordinary or ‘active’ condition; reducing agents tend to restore ‘activity’. Similarly, anodic treatment may produce passivity, but cathodic treatment usually renders the metal active again. Low temperatures favour continuation of passivity, and high temperatures a return to activity; alkalis are favourable to passivity, and non-oxidising acids to activity. These facts cannot fail to suggest that passivity is due to a protective oxide film.
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References
Phil. Trans., 80, 374; 1790.
Phil. Mag., 9, 53; 1836.
Phil. Mag., 9, 57; 1836.
Wiedermanns Ann. Phys. Chem., 36, 532 865; 1889: 39, 481 1890.
Jour. Chem. Soc., 972; 1928.
Jour. Chem. Soc., 1038; 1927.
Archives des Sciences physiques et naturelles (Genéve), 10, 125–127; 1900.
Zeit. physik. Chem., 138, 123; 1928.
Jour. Inst. Met., 29, 534; 1923.
S. C. Britton and U. R. Evans, Jour. Chem. Soc., 1773; 1930.
Jour. Chem. Soc., 1020; 1927: 92 and 2651; 1929: 478, 1361, and 1773; 1930.
Zeit. physik. Chem., 128, 321; 130, 289; 1927.
Even in a neutral sodium sulphate solution, Lobry de Bruyn Rec. Trav. Chim., 40, 53; 1921 has found that 1 per cent of the current at a passive iron anode is devoted to the dissolution of iron. In acid solution, W. J. Müller (Zeit. Elektrochem., 36, 682; 1920) has found that about 4 per cent of the current is expended on the dissolution of iron.
Monatshefte für Chemie, 48, 611; 1927. Zeit. physik. Chem., Bodenstein Festband, 687; 1931.
Zeit. Elektrochem., 34, 577; 1928.
L. McCulloch (Trans. Amer. Electrochem. Soc., 56, 325; 1929) has suggested that a layer of ferric sulphate—a salt which is only slowly soluble in water—contributes to the passivity.
Jour. Chem. Soc., 2880; 1926.
"Optische Untersuchungen zur Frage der Passivität des Eisens und Stahls"; Dissertation, Trondheim (1931). Also Zeit. physik. Chem., A, 142, 241; 1929.
Jour. Chem. Soc., 480; 1930.
NATURE, 126, 130; 1930.
E. S. Hedges, "Protective Films on Metals" (Chapman and Hall): in the press. Jour. Chem. Soc., 2878; 1926: 969; 1928: 1028; 1929.
Zeit. Elektrochem., 12, 49; 1906.
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EVANS, U. The Passivity of Iron. Nature 128, 1062–1065 (1931). https://doi.org/10.1038/1281062a0
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DOI: https://doi.org/10.1038/1281062a0
