Abstract
WHEN a clean surface of metal is heated gently in air, a fine series of colours is often produced, the sequence of tints being that which would be expected from optical principles. In the case of lead, four ‘orders’ of tints can be observed: red, for example, occurs four times in the sequence. The transparent oxide film which is responsible for the effect can be lifted from the lead, and it is found that for any given film the colour as seen by reflected light is complementary to that seen by transmitted light. On copper and iron the sequence is essentially the same as on lead, but the fourth-order tints (corresponding to fairly thick films) cannot be seen; indeed on iron—no doubt owing to the low transparency of the oxide—only the first-order colours are really bright, although, if the oxidation is carefully carried out, the sequence can easily be followed as far as the third-order red.
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Based on two lectures on the "Tinting, Tarnishing, and Corrosion of Metals," delivered at the Royal Institution on May 20 and 27.
This yellow colour is due to the characteristic tint of ferric hydroxide, and in no way resembles the yellow temper colour.
American Chemical Society Corrosion Symposium, 1925. See Ind. Eng. Chem., 17, 1925, 370.
J. Chem. Soc., 127, 1925, 2605.
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EVANS, U. Oxidation, Passivity, and Corrosion1. Nature 118, 51–53 (1926). https://doi.org/10.1038/118051a0
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DOI: https://doi.org/10.1038/118051a0