Characterization of “Cu-Milk Corrosion”

Carvalho, Luciana da Costa

doi:10.1007/978-3-030-97892-1_4

Cited by 3 publications

(8 citation statements)

References 15 publications

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“…However, cholesterol and its oxidation products have been identified in carbonized residues found in copper cauldrons 20 , where the presence of copper ions has been suggested to have contributed to their preservation. It is also relevant that only cholesterol (not its oxidation products) was identified in modern freeze-dried milk and copper-milk corrosion 33 analysed by the same GC-QTOF-MS with TSP method used in this study, and no sterols have been identified in any other sampls from the Pewsey Hoard.…”

Section: Resultsmentioning

confidence: 95%

“…Indeed, corrosion experiments have demonstrated that copper ions readily react with organic and inorganic ligands in the same medium 31 forming copper-organic complexes and characteristic inorganic phases. Moreover, the low solubility of copper-organic complexes in organic solvents 32 and/or the presence of copper ions negatively impact the recovery of organic residues by typical gas chromatography with mass spectrometry protocols 33 . Thus the discovery of the Pewsey Hoard provided a unique opportunity to investigate archaeological corrosion from difference vessels with the same deposition context by incorporating techniques targeting both inorganic and organic compounds.…”

Section: Introductionmentioning

confidence: 99%

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Unlocking the organic residues preserved in the corrosion from the Pewsey Hoard vessels

Carvalho

Henry

McCullagh

et al. 2022

Sci Rep

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The characterization of archaeological metal corrosion has traditionally been limited to the identification of inorganic compounds usually by X-ray diffraction (XRD), thought to result from the interaction between the metal object and the deposition environment. The discovery of a hoard of Late Roman copper-alloy vessels in Wiltshire, UK presented an unique opportunity to adopt a multi-analytical approach to characterize corrosion combining XRD with Fourier-transform infrared (FTIR) and gas chromatography with quadrupole time-of-flight mass spectrometry using a thermal separation probe (GC-QTOF-MS with TSP). This approach revealed organic compounds potentially historical preserved within crystalline inorganic matrices. It has been known for some time that ceramics can harbour organic residues, which provide crucial evidence about the use of these vessels in the past. Our results confirms that similar residues appear to survive in metal corrosion thus extending the potential for identification of biomaterials used in the past.

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Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Unlocking the organic residues preserved in the corrosion from the Pewsey Hoard vessels

Carvalho

Henry

McCullagh

et al. 2022

Sci Rep

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“…Short and medium chains (C6, C8, and C10) allow exibility of movement, with FA molecules managing to effectively anchor on the metal surface and promote the reaction described in Eq. 6 of the following scheme [40,41,76]…”

Section: Reactivity and The Intermediatementioning

confidence: 99%

“…Copper soaps have been detected on the surface of beeswax-covered metal objects, and explanations were offered to rationalize this as the result of the reaction between the copper metal and free fatty acids formed after wax degradation [34,35]. A proof of concept has been recently offered by a young researcher, illustrating the electrolytic formation of copper palmitate on the surface of copper coupon serving as the anode [41]; evidence for the formation of this speci c soap was offered through FTIR and XRD.…”

Section: Introductionmentioning

confidence: 99%

“…Speci cally, the antisymmetric infrared maxima reported for copper carboxylates to be at higher values (1585 cm − 1 ) than those of the zinc carboxylates with an additional one at 1508 cm − 1 , while the symmetric band is found at 1415 cm − 1 [44,51] giving a Δ value of 170 cm − 1 . Additionally, copper carboxylate infrared spectra have been reported to assume multinuclear coordination geometries [41,44,55], although clear data have been shown for the binuclear complexes, where two Cu(II) ions are bridged through four carboxylate units [51,52]. These geometries are established on the basis of multiple carboxylate maxima (or 'multiplets') as shown below.…”

Section: Introductionmentioning

confidence: 99%

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Infrared spectroscopy reveals the reactivity of fatty acids on copper surfaces and its implications for cultural heritage objects

Boyatzis

Fragkos-Livanios

Giannoulaki

et al. 2023

Preprint

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The reactivities of various fatty monoacids and diacids on copper metal-containing surfaces were investigated through reflection-absorption infrared spectroscopy. The formation of copper soaps is detected on pure copper surfaces, while copper and zinc soaps are simultaneously formed as mixtures on brass surfaces. Following the changes of acidic carbonyl and carboxylate infrared bands, it is shown that fatty monoacids C8, and C10 react with clean/polished copper and its zinc alloy within 2–4 hours, while those with chains > C12 react within 15–40 days. An explanation for the above results is offered on a molecular mobility basis, where liquid monoacids at room temperature favour higher reaction rates. Furthermore, it is argued that longer-chain FMAs allow for favourable orientation resulting in self-assembled monolayer (SAM)-type molecular packing on Cu surface, may explain the slower reaction. Fatty diacids, on the other hand, do not form any carboxylate products under these conditions. In light of this interesting result, it is argued that dicarboxylic acids may also pack as self-assembled layers on Cu and ultimately protect it. The implications for fatty organic remains in copper containers are discussed, with emphasis on the stability of archaeological copper metal and carboxylates serving as molecular markers for the presence of fatty monoacids as residues in archaeological containers. Besides, the utilization of fatty acids, based on the above behaviour in copper-based dosimeters, such as those used in the Oddy test, is suggested.

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Infrared spectroscopy reveals the reactivity of fatty acids on copper surfaces and its implications for cultural heritage objects

Boyatzis,

Fragkos-Livanios,

Giannoulaki

et al. 2023

Herit Sci

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The reactivities of various fatty monoacids and diacids on copper metal-containing surfaces were investigated through reflection–absorption infrared spectroscopy. The formation of copper carboxylates is detected on pure copper surfaces, while copper and zinc carboxylates are simultaneously formed on brass surfaces. Following the decrease of acid carbonyl and the formation of carboxylate infrared bands, it is shown that fatty monoacids C8 and C10 react with clean/polished copper and its zinc alloy within 2–4 h, while those with chains > C12 react within days. At the end of the processes, only the corresponding metal carboxylates are detected in all cases. An explanation for the above is offered on a molecular mobility and acidity basis, where the lower monoacids (liquids in room temperature), also having lower pKa values, favor higher reaction rates. Furthermore, it is argued that longer-chain fatty monoacids, when deposited from their solutions, allow for favorable orientation resulting in self-assembled monolayer-type molecular packing on the copper surface, which may additionally rationalize the slower reaction. Interestingly, fatty diacids do not form any carboxylate products under the same conditions, as it is argued that their molecules may efficiently pack as self-assembled multilayers on copper and ultimately protect it. The possible implications of the fatty monoacid and diacid behavior on the archaeological organic residues level and regarding the stability of copper alloys are discussed.

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Characterization of “Cu-Milk Corrosion”

Cited by 3 publications

References 15 publications

Unlocking the organic residues preserved in the corrosion from the Pewsey Hoard vessels

Unlocking the organic residues preserved in the corrosion from the Pewsey Hoard vessels

Infrared spectroscopy reveals the reactivity of fatty acids on copper surfaces and its implications for cultural heritage objects

Infrared spectroscopy reveals the reactivity of fatty acids on copper surfaces and its implications for cultural heritage objects

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