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Brass and Glass: Crystal Structure Solution and Phase Characterisation of the Corrosion Product Zn 4 Cu 3 (Zn 1 – x Cu x ) 6 (HCOO) 8 (OH) 18 ·6(H 2 O)
Author(s) -
Bette Sebastian,
Fischer Andrea,
Stelzner Jörg,
Eggert Gerhard,
Dinnebier Robert E.
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201801420
Subject(s) - zinc , chemistry , crystal structure , crystallography , copper , octahedron , zinc hydroxide , x ray crystallography , corrosion , inorganic chemistry , diffraction , physics , organic chemistry , optics
The title compound, Zn 4 Cu 3 (Zn 1– x Cu x ) 6 (HCOO) 8 (OH) 18 · 6(H 2 O), also denoted as “Zinc C”, a previously unknown corrosion phase of brass in contact with glass, was found on four different historic objects stored in three different collections. Model experiments demonstrated that formaldehyde emitted e.g. from wooden cabinets undergoes a Cannizarro reaction in the alkaline surface film on the historic glass making formate available for the formation of this corrosion phase. The crystal structure of “Zinc C” was solved ab initio from X‐ray powder diffraction data. From the crystal structure and EDX analyses, a phase composition of Zn 4 Cu 3 (Zn 1– x Cu x ) 6 (HCOO) 8 (OH) 18 · 6(H 2 O) was derived. Zinc C crystallizes in a trigonal unit cell in space group R 3 (148) with lattice parameters of a = 10.9185(1) Å, c = 27.5058(4) Å, and V = 2839.74(6) Å 3 . Layers of edge sharing MO 6/3 octahedra with voids capped by Zn(HCOO) forming Zn(HCOO)(OH) 3/3 tetrahedra are the main motif in the structure. The zinc/copper ratio of the corrosion phase “Zinc C” can vary between 10:3 and 4:9, due to a partial occupational disorder between copper and zinc in the crystal structure.