Corrosion of brass in a marine environment: mineral products and their relationship to variable oxidation and reduction conditions |
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| Institution: | 1. Microchem Geochemistry Consultants, 508 East Jeddore Road, East Jeddore, Nova Scotia Canada B0J 1W0;2. Emeritus Scientist, Geological Survey of Canada, Atlantic, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada B2Y 4A2;3. Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, 78712, USA;1. Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083, China;2. Department of Physics, Tsinghua University, Beijing 100084, China;3. Cloud Computing Department, Beijing Computing Center, China;4. The 20 Middle School of Beijing, Beijing 100085, China;5. Department of Physics and Hebei Advanced Thin Film Laboratory, Hebei Normal University, Shijiazhuang 050024, Hebei, China;1. Faculty of Information Science and Engineering, Ningbo University, Ningbo 315211, China;2. Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, Ningbo, Zhejiang 315211, China |
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| Abstract: | Minerals coating brass ammunition shells that rested at the bottom of Halifax Harbour, Nova Scotia, for 52 a have been identified by X-ray diffraction and analytical scanning electron microscopy. The admiralty brass shells, partially buried in anoxic muds, straddle a strong Eh gradient ranging from 0 mV to values characteristic of oxygenated seawater. Whereas the brass surface in contact with the sediment has been preserved, parts of the shells exposed to seawater have corroded throughout their thickness. The corrosion products identified include metallic Cu, djurleite (Cu1.96S), cuprite (Cu2O), atacamite (Cu2Cl(OH)3), spertiniite (Cu(OH)2) and hydrozincite (Zn5(CO3)2(OH)6). These products are those predicted thermodynamically on the basis of ambient Eh and pH. However, this study also revealed the presence of a mineral not previously known to exist and tentatively identified as Cu14Zn14Cl5(SO4)5(OH)41.H2O. This “new” mineral seems to have a stability field in Eh–pH diagrams similar to that of connellite (Cu19Cl4SO4(OH)32.2H2O). |
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