Ein dem Malachit ähnliches basisches Eisenkarbonat als Korrosionsprodukt von Stahl |
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Authors: | E. Erd s,H. Altorfer |
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Affiliation: | E. Erdös,H. Altorfer |
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Abstract: | A basic ferrous carbonate similar to malachite as a corrosionproduct of steel A formerly unknown basic ferrous carbonate is described, which was found on the cone of a hot water valve (temperature 180°C) together with siderite and magnetite. According to analysis the formula is Fe1,82+Fe0,22+(OH)2,2CO3 or “Fe2(OH)2CO3” with some amorphous ferric oxidehydrate. The unit cell of said compound is orthorhombic: a = 9,390Å; b = 24,53 Å; c = 3,212 Å; Z = 8 aspect p* ab. The measured density: 3,59 g · cm?3. An infrared spectrum was taken and the frequencies of absorption coordinated tentatively with vibrations between 800–500 cm?1. Thermal analysis in oxygen leads to a stepwise exothermic decomposition and oxidation in course of which above 197°C an intermediate metastable compound (ferric oxidecarbonate “Fe2O2CO3”) is topotactically formed. The unit cell of this compound is orthorhombic: a = 9.23 Å; b = 12,18 Å; c = 5,94 Å. Also in this case an infrared spectrum was taken and bonds coordinated. Above 360°C further decomposition leads the formation of hematite. Decomposition in argon starts at 300°C. The reaction is endothermic and the product magnetite. A structural relationship exists between “Fe2(OH)2CO3” and malachite and also to siderite. In this latter case we assume epitaxial relations. |
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