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Review

Curious Corrosion Compounds Caused by Contact: A Review of Glass-Induced Metal Corrosion on Museum Exhibits (GIMME)

by
Gerhard Eggert
* and
Andrea Fischer
Institute of Conservation Sciences, State Academy of Art and Design, 70191 Stuttgart, Germany
*
Author to whom correspondence should be addressed.
Corros. Mater. Degrad. 2022, 3(3), 553-565; https://doi.org/10.3390/cmd3030030
Submission received: 31 July 2022 / Revised: 20 August 2022 / Accepted: 9 September 2022 / Published: 16 September 2022
(This article belongs to the Special Issue Cultural Heritage Materials Degradation and Its Prevention)
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Abstract

:
Many heritage objects consist of glass in contact with metals. By ion exchange with absorbed water, alkaline aqueous films are formed on the glass surface. They contain sodium and/or potassium, hydroxide, and carbonate (uptake of carbon dioxide) ions. These electrolytes induce corrosion while in contact with metal. Surprisingly, this phenomenon has only been realised by research in Stuttgart in the last two decades. About 350 affected objects were detected in the meantime in a number of heritage collections. Because of the special electrolytes, unusual corrosion products are often formed. The unknown structure and formula of three of them could be determined by modern X-ray powder diffraction data evaluation. One example is the basic potassium lead carbonate, KOH‧2PbCO3, detected on a pewter lid of a glass jug. The sodium analogon of already known structure was found in hollow glass balls mirrored on the inside with molten lead. Chalconatronite, Na2[Cu(CO3)2]‧3H2O, is known as a corrosion product of copper alloys in contact with soda solutions (here: from glass degradation). Exposed to acetic acid emissions (e.g., from wood), it transforms to a sodium copper acetate carbonate of hitherto undetermined structure. The ubiquitous pollutant formaldehyde reacts directly to formate in the alkaline medium provided by glass degradation. On copper alloys in contact with glass, formates are, therefore, frequent: Na4Cu4O(HCOO)8(OH)2‧4H2O in 50% of all cases and in 33% Cu2(HCOO)(OH)3. Zinc (from brass) forms Zn(HCOO)2‧2H2O and Zn4Cu3(Zn1−xCux)6(HCOO)8 (OH)18·6H2O. There are a number of other corrosion products, e.g., containing zinc and carboxylates awaiting further characterisation. Preventive conservation needs to slow down corrosion by dry storage (not lower than 35% rH). Pollutants need to be avoided by careful selection of materials for storage, display, and conservation.

1. Introduction

Conventional corrosion science is interested in corrosion rates. Things are different in heritage science: the corrosion of heritage objects is quite slow (with few exceptions) and occurs over milennia or centuries in the atmosphere or in soil or water. Corrosion in the museum environment usually takes decades or at least years. Therefore, heritage science rarely studies rates (kinetics), but the products of corrosion (thermodynamics). As part of the ‘biography‘ of an object, they can give hints of what happened to them. Furthermore, even after 250 years of research on the corrosion of historic materials, there are still new products and mechanisms to be discovered. This paper reviews glass-induced metal corrosion products on museum exhibits (GIMME) as studied at the Institute of Conservation Sciences of the Stuttgart State Academy of Art and Design. Typical for GIMME is metal corrosion in the contact zone with glass and often nowhere else on the metal. From 2006 to 2012, only 13 relevant objects could be discovered [1,2]. The number increased considerably during the intensive PhD research of Andrea Fischer [3]. Cases of individual compounds were published in a series of papers ‘When Glass and Metal Corrode Together I-VII’ (see references). Now some 500 samples from 350 objects in more than 40 collections were analysed providing a general overview of the GIMME phenomenon. Recently, other researchers also published GIMME corrosion product identifications [4,5,6].

2. Corrosion Factors and Their Investigation

Atmospheric metal corrosion needs oxygen and humidity, both provided by the air, but also electrolytes. The self-dissociation and, therefore, the conductivity of pure water is very low. In equilibrium with carbon dioxide from the air (currently 420 ppm), some carbonic acid yielding hydrogencarbonate and hydronium ions (pH ca. 5.6) is formed; the conductivity is increased but still quite low. Acid pollutant gases like SO2 and NOx forming sulfate and nitrate ions can add to ionic strength. It took until 2010 [1] for another important source for ions in the corrosion of metal exhibits to be realised: the contact of degrading historic glass with its alkaline surface films.

2.1. Glass as Source of Electrolytes

Quartz (SiO2) as a glass network former consists of a three-dimensional network of strong Si-O bonds, and therefore has a melting point beyond the capability of historic coal or wood-fired furnaces. Network modifiers such as the fluxes soda (Na2CO3) or potash (K2CO3) or stabilisers like lime (CaCO3) have to be added for glass production. They release CO2 on heating and the O2− anion from the remaining oxides attacks the Lewis acid Si(+IV) and scissors oxygen bridges in the network. In the case of soda this can be written as:
≡Si-O-Si≡ + O2− + 2 Na+ → ≡Si-O−Na+ + Na+ −O-Si
At normal humidity, glass is covered by ca. three monolayers of water [7]. The surface of glass tends to be alkaline as an ion exchange with surface water occurs:
≡Si-O−Na+ + H2O → ≡Si-O-H + Na+OH−
The surface films on glass provide Na+ and/or K+ and OH− ions for further reaction. In metal corrosion compounds, oxide (O2−) ions can form when the oxide is thermodynamically more stable than the hydroxide, e.g., [8]:
Cu + ½ O2 + H2O → Cu(OH)2 → CuO + H2O
The alkaline films on the glass absorb carbon dioxide from the atmosphere which forms carbonate ions (CO32−). As magnesium and calcium carbonate are quite insoluble at pH > 7, concentrations of Ca2+ and Mg2+ (from the stabiliser) in the alkaline films are very low and, therefore, do not find their way into metal corrosion products. This situation is different for church windows exposed to acid rain (pH 4.6), where gypsum and other sulfates appear in weathering crusts and alkali compounds are washed away. Despite the dominance of sulfates like brochantite in outdoor corrosion of copper alloys, no sulfates have been detected in GIMME indoor corrosion products. The same holds true for nitrate. Nitrates, such as the basic copper nitrates rouaite and gerhardtite, are in general very rarely found in atmospheric corrosion of not artificially patinated metals.
Carbonyl pollutants play an important role in corrosion reactions of museum objects [9]. They comprise the C1 and C2 alkanoic acids and aldehydes: formic (IUPAC: methanoic) and acetic (IUPAC: ethanoic) acids as well as formaldehyde (IUPAC: methanal, H2CO) and acetaldehyde (IUPAC: ethanal, CH3CHO). Wood and wood products are the major source of these pollutants [10]. They are incorporated into corrosion products as formate (methanoate, HCOO-) and acetate (ethanoate, CH3COO−). The alkaline glass films are able to absorb aldehydes and to transform them directly to the corresponding acid (without intermediate adsorption and oxidation steps) via the alkali-catalysed Cannizzaro reaction:
2CH2O + OH− → HCOO− + CH3OH
Volatile methanol (CH3OH) is co-produced in this disproportionation reaction and has recently been detected [11]. Formate is collected in the films because formaldehyde is a ubiquitous air pollutant originating from many sources [12] and museum objects are exposed to it over decades or centuries. Therefore, it is not surprising that formate often dominates as anion on glass surfaces [13] and enters metal corrosion products.
Glass-induced metal corrosion could be successfully reproduced in desiccator experiments when metal coupons (soaked in alkali carbonate solution and then dried) were exposed to vapours from formaldehyde solutions [14].
The corrosive effects of acetic acid emitted from oak have long been known in museums. Calcium carbonate (calcite or aragonite) based materials as found in Natural History collections (shells, eggs, pearls, etc.) are prone to acetate containing efflorescence (‘Byne’s disease’) and a number of compounds have been characterised [15]. As formic acid, acetic acid is absorbed and neutralised in the glass films, providing acetate ions for further reactions.

2.2. Metals Prone to GIMME

Antiquity and Mediaeval Europe knew seven metals which were aligned to the days of the week and the movable celestial bodies: Gold (Au), silver (Ag), iron (Fe), mercury (Hg), tin (Sn), copper (Cu), and lead (Pb). Mercury (present in fire-gilded layers), gold, and silver are too noble for GIMME corrosion. However, historic silver always contains at least some percent of copper from production or intentionally alloyed to increase hardness. Copper is preferentially corroded in such alloys; hence, only copper compounds have been discovered on silver. Tin and iron form very stable oxide/hydroxides during corrosion; no specific compounds containing other ions were discovered during GIMME research. Lead is known to favour basic carbonates in corrosion, but in the presence of alkali carbonates, compounds containing Na+ or K+ can form (see below). Copper and its alloys (brass, bronze) in contact with glass frequently show contact corrosion; most often, formates are formed. This also holds true for zinc occurring in brass. Pure zinc (recognised in Europe since the 18th cent.) and other zinc alloys have not been surveyed yet for GIMME. The same holds true for other modern metals like nickel or cadmium.

2.3. Historic Objects with Contact between Glass and Metals

Many types of heritage objects consist of glass in contact with metal.

2.3.1. Fused Contact

The closest contact is achieved when glass (e.g., enamel) is directly fused onto metal. Early unstable Limousin painted enamels are particularly at risk of glass-induced metal corrosion, but examples of corrosion were also identified on enamel champlevé and enamel cloissoné. Glass figures were often fused onto a wire support and show corrosion in cracks were metal is exposed.

2.3.2. Tight Mechanical Contact

Other objects achieve close contact by mechanical pressure: metal-mounted glass vessels, glass gems in bezels (often found in folk jewellery), and cover glasses on metal (glass-framed miniatures or daguerreotypes with metal passe-partouts, watches), lenses held by metal (spectacles, optical instruments), glass levels mounted in brass, miners‘ lamps, and electric bulbs.

2.3.3. Loose Contact

The contact can also be loose as in glass elements (e.g., beads) on metal wires. Often the loss of glass elements was caused by the total corrosion of thin wires on traditional bridal crowns, reliquaries, and Christmas tree baubles. Only in these objects, the contact between metal and glass can be prohibited by the use of coatings (Paraloid B-72 works for both materials) or plastic separation layers.

2.3.4. No Direct Contact

The induction of metal corrosion by glass is mediated by liquid electrolytes caused by glass degradation. Such electrolytes are somewhat mobile. Therefore, corrosion has also been observed outside the direct contact zone when drops run down a vessel over a metal mounting or drip from cover glasses on metal below.

2.4. Analytical Identification Methods

In Stuttgart, the identification of compounds was mainly performed by Raman microscopy, but energy dispersive X-ray spectroscopy in the scanning electron microscope (EDX-SEM) and X-ray powder diffraction (XRPD) were also employed (for experimental details see [16]). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) could also be used for the identification of compounds [5]. Marchetti et al. [6] demonstrated the usefulness of the novel optical photothermal infrared (O-PTIR) spectroscopy that allows to noninvasively obtain chemical information at a submicrometric scale with high spatial resolution without need for sample preparation. The spectral results are comparable to traditional FTIR.
A breakthrough in characterising unknown compounds was achieved by modern high precision XRPD. Sophisticated methods of data evaluation at the Max Planck Institute of Solid State Research even allowed the determination of complicated crystal stuctures with low symmetry from powders [17]; single crystals are no longer mandatory. Chemical formulae of compounds automatically follow from such structure determinations.

3. GIMME Corrosion Compounds

Depending on the metal and the availability of anions, a number of corrosion compounds can form by glass-induced metal corrosion. These are systematised here along with the anions present (carbonate or formate, Table 1).

3.1. Carbonates ①–④

In a first approximation, glass-induced metal corrosion can be understood as metal corrosion in the presence of alkali carbonate solutions.

3.1.1. NaPb2(CO3)2(OH) ①

Kutzke et al. [23] detected ① instead of the expected lead carbonates (‘lead white’) as a pigment in a white ground layer of an iron lattice in the church of Oberwesel. They referred to an old publication by Auerbach and Pick [24] which showed that the common corrosion products cerussite and hydrocerussite are transformed into ① in the presence of a soda solution. ① can indeed be produced as a corrosion product on lead foil (Figure 1).
Therefore, it was predicted to be a GIMME corrosion product [1]. While a search on glass window panes in lead cames failed, hollow glass spheres from bridal crowns mirrored on the inside with molten lead provided 16 samples from five museums [18].
These baubles were often mounted on copper wires which tended to corrode in contact with glass. Many wires broke, causing glass baubles to drop and break. This allowed the sampling of corrosion products on the interior lead (Figure 2). ① was also discovered on a leaded glass mirror element on a 19th century south-east Asian lacquered Buddha statue [25]. Incidentally, ① has now also been found as a supergene mineral named abellaite [26].

3.1.2. KPb2(CO3)2(OH) ②

Glasses produced with potash instead of soda as flux are rich in potassium. In one case, ②, the potassium analogon of ① could be identified on the pewter (tin-lead alloy) mounting of a beer jug together with SnO and PbCO3 (Figure 3). In a replication experiment, immersion of a lead coupon in 2 M K2CO3 also yielded ②. XRPD data from a sample prepared by hydrothermal synthesis allowed the solving of the crystal structure [19].

3.1.3. Na2[Cu(CO3)2]∙3H2O ③

Sodium dicarbonato cuprate(II) trihydrate ③, as a mineral called chalconatronite, is formed when copper corrodes in the presence of soda, e.g., in soda-rich Egyptian soil or during conservation treatments with sodium sesquicarbonate. Therefore, it is not surprising that it also occurs as a GIMME corrosion product in ca. 5% of all cases with glass degradation as the soda source [20]. Chalconatronite was detected on set gems in Baroque reliquaries (Figure 4), enamel on metal, Christmas tree decoration, glass buttons, a glass figure with a copper wire support, miners’ lamps, and a glass-framed daguerreotype [20]. In the latter case, the corrosion product was originally identified as Na3[Cu2(CO3)3(OH)]‧4H2O, ICDD 00-28-1084 [27] based on the original publication of this compound [28]. Evaluation of their XRD peak list and their FTIR spectra and own synthesis experiments proved that the compound was nothing other than chalconatronite [29]. Consequently, ICDD deleted the chart.

3.1.4. NaCu(CH3COO)(CO3)∙nH2O ④

Thickett and Odlyha [30] discovered ④ on Egyptian bronzes in the British Museum stored for a long time in oak cupboards. This is most likely a conversion product of ③ when exposed to acetic acid, as desiccator experiments by Paterakis [31] have shown. The amount ratio for all ions was found to be equal; thermogravimetry pointed to some crystal water and possibly hydroxide [30]. Experiments to synthesise a pure powder sample for structure determination have not succeeded so far. Fischer [3] identified four GIMME cases where the compound occurred, always in mixtures, e.g., on a hat pin (Figure 5).
There is also evidence for a potassium analogon (EDX-SEM: K, no Na, but Raman spectrum very similar [3]).

3.2. Formates ⑤–⑧

Formates are rarely found as corrosion products on metals without glass contact [32]. However, the majority of the analysed glass-induced metal corrosion samples contained formate due to formaldehyde pollution and the Cannizzaro reaction in the alkaline surface films on glass (Equation (4)). The corrosion can be simulated in desiccator experiments by exposing metal coupons soaked in alkali carbonate solutions and then dried to formaldehyde vapours [14].

3.2.1. Cu4Na4O(HCOO)8(OH)2∙4H2O ⑤

Trentelman et al. [33] were the first to describe and characterise a ‘new pale blue corrosion product’ on a number of ancient Egyptian, Greek, Assyrian, and Chinese copper alloy finds (no glass contact). Based on their detailed investigation they had assumed ⑤ to be a sodium copper formate acetate. The crystal structure could be determined by us from XRPD measurements and resulted in the formula Cu4Na4O(HCOO)8(OH)2·4H2O [34], a basic sodium copper formate, also containing an oxide anion and water of hydration. In the structure, there is no acetate present. The acetate detected by ion exclusion chromatography [16] might be adsorbed on the surface of crystals. Indeed, the compound can be produced without acetic acid or acetate by exposition of chalconatronite or metal coupons immersed in soda solution to formaldehyde and formic acid vapours [34]. The name socoformacite, coined by us based on [33] as an abbreviation of sodium copper formate acetate [35,36], is now outdated and incorrect.
Basic sodium copper formate ⑤ was found by us as the most frequent GIMME corrosion product (50% of all samples) using mainly μ-Raman spectroscopy [3]. Examples for its occurrence include all kinds of historic objects with glass in contact with copper alloys (see above), for example, glass vessels with metal mountings (Figure 6). More details on objects and figures are reported by Fischer et al. [16].

3.2.2. Cu2(HCOO)(OH)3 ⑥

Copper formate trihydroxide (IUPAC name; colloquial: dicopper trihydroxyformate) is the second most frequent GIMME corrosion product (ca. 33% of all cases [3]). It often occurs together with ⑤ which indicates that the conditions for formation must be similar. For instance, both copper formates were found on replicas of an enamelled altarpiece that were produced 1954–1956 using historical recipes [5]. On potash glass with no sodium available, ⑥ occurs of course alone. An example of an unstable potash copper ruby glass mounted in gilded silver is shown in Figure 7.
Eggert et al. [37] discovered ⑥ also on a silver-mounted glass flute, enamel on copper, and brass mattes in glass-framed daguerreotypes. Veiga et al. [4] reported ⑥ on three miniatures of the Evora museum painted on copper with a cover glass.
⑥ is known to need a pH > 8 for precipitation, which is provided by corroding glass. By chance, copper patination experiments with formic acid and ammonia yielded a single crystal suitable for structure determination [38].

3.2.3. Zn(HCOO)2∙2H2O ⑦

Only a few occurrences of ⑦ without glass contact have been reported [32], e.g., on zinc coins in chipboard drawers. These cases are now outnumbered by the twelve GIMME cases discovered in four Swiss and German museums [21]. They were all found on the copper-zinc alloy brass. An example is the bezel of a pocket watch in contact with an unstable glass (Figure 8); note the drops formed by hygroscopic salts from glass degradation on the interior side of the cover. The green-blue compound ⑤ dominates, but there are also white particles that contain only zinc and no copper (SEM-EDX). They could be identified as ⑦ by XRPD and μ-Raman spectroscopy. The source for formaldehyde was evidently the chipboard used for storage for over 30 years.

3.2.4. Zn4Cu3(Zn1–xCux)6(HCOO)8(OH)18·6(H2O) ⑧

Zinc and copper were found as the main cations by EDX-SEM in the compound labelled ‘Zinc C’; the Raman spectrum pointed to a basic formate. Corrosion samples were always multiphase. However, a pure sample could be obtained by corroding a brass (CuZn10) coupon dipped in aqueous potassium hydrogencarbonate at 76% RH with vapours from 4% aqueous formaldehyde [21]. This pure sample allowed the determination of the crystal structure [22] with different crystallographic sites for the cations. An octahedral site can be occupied either by zinc or copper which makes the stoichiometry somewhat flexible. The compound was detected on 12 objects of various types. A metal clamp holding a reagent tube showed that GIMME can also be found on 20th century objects (Figure 9).

3.3. Uncharacterised Compounds

Because of a lack of suitable samples of pure and ideally crystalline material there are still a number of GIMME compounds waiting for their full characterisation [3]. They contain Na, K, Cu, and/or Zn (EDX-SEM) and are often carboxylates (Raman). One example is the corrosion product of the enamel of a procession cross in the British Museum (K, Cu, and formate). As it was also found in simulation experiments [14], it might be possible to obtain sample material for further studies in the future. The crystalline compound labelled Zinc A contains zinc and sodium and possibly a little copper and is most likely an acetate [21]. ‘Zinc B’ contains more potassium than zinc and often occurs together with the copper formates ⑤ and ⑥ [21].

4. Conclusions

Understanding corrosion is a prerequisite for rational-based conservation. Corrosion products need to be identified to learn more about the environmental conditions that objects were exposed to. Surprisingly, we found still large knowledge gaps. The crucial role of glass degradation providing electrolytes for metal corrosion was hitherto not understood. While formates are rare among normal metal corrosion products [32], we found that they dominate on copper alloys in contact with glass due to the alkali-catalysed Cannizzaro reaction. Astonishingly, GIMME found until recently no attention, although our surveys in the Swiss National Museum [39] and the Deutsches Bergbaumuseum [40] discovered that severe cases, which ‘catch the eye’ (as depicted here in the figures), are found on 1–2% of all combined glass/metal objects. Light cases (‘hardly recognisable’) are in the range of 10–20%. One can safely predict that GIMME cases can be found in every large collection of composite glass-metal objects.
In the past, corrosion studies were often obstructed by the lack of reference data for compounds. Crystal structure determination from modern high precision powder diffraction proved to be a new, invaluable tool for conservation science [17]. Although the reciprocal space for single crystals is reduced to one dimensional d-spacing for powders, there is still enough information which allows the determination even of complicated structures and their incidental chemical formulae. More sampling and more laboratory reproduction experiments are required to further close the knowledge gap. A number of GIMME corrosion products are still waiting for characterisation.
Preventive conservation must prohibit further corrosion as far as possible. The principal cause, the sensitivity of glass to hydrolysis and its contact with metal, cannot be changed for most objects. Material degradation of glass and metal can be slowed down by reducing the relative humidity. However, to avoid drying cracks (‘crizzling’) in the silica gel layers formed by glass degradation, one should not go below 35% rH. Formaldehyde can be avoided by proper selection of materials for display, storage, and conservation. If sources like wood are part of the objects themselves, absorbents like active charcoal should be placed in display cases. Saturated salt solutions, sometimes used for controlling relative humidity in display cases, were recently found to also be excellent formaldehyde absorbers [41]. A saturated solution of potassium carbonate (pH = 11.3) placed in display cases can both climatise to 43% RH and absorb acid gases and aldehydes. This may provide a valuable alternative for museum practice as will be explored in a new research project funded by DBU.
Corrosion is a large-scale economic problem in our modern world. For irreplaceable cultural heritage objects, it is more than that. Material documents of human endeavours, and with it our identity and societal memory, are endangered. Preventive conservation guided by corrosion studies will hopefully help to reduce GIMME cases in the future and preserve our cultural heritage for generations to come.

Author Contributions

G.E. developed the research idea and started with measurements. A.F. conducted systematic examinations of objects and corrosion samples as part of her Ph.D. thesis supervised by G.E.; G.E. wrote the draft. All authors have read and agreed to the published version of the manuscript.

Funding

GIMME research was funded from 2012–2015 by Friede Springer Stiftung and from 2016–2019 by DBU (Az. 33255/01). The crystal structure determinations were part of the ‘In search of structure’ project (2017-2/2020) funded by DFG (grant EG 137/9-1). Travel grants were provided by ARCHLAB and DAAD.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

C. Krekel (ABK Stuttgart) provided access to EDX-SEM and Raman microscopy in his Heritage Science Laboratory. J. Stelzner (ABK Stuttgart) performed measurements within the DBU project. S. Bette and R.E. Dinnebier solved crystal structures within the DFG project.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. FE-SEM BSE image of hexagonal NaPb2(CO3)2(OH) crystals grown on lead foil in Na2CO3 solution (Photo: Dirk Kirchner).
Figure 1. FE-SEM BSE image of hexagonal NaPb2(CO3)2(OH) crystals grown on lead foil in Na2CO3 solution (Photo: Dirk Kirchner).
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Figure 2. Broken lead coated glass sphere from a bridal crown) (Photo: Stephanie Wümmers).
Figure 2. Broken lead coated glass sphere from a bridal crown) (Photo: Stephanie Wümmers).
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Figure 3. (a) Potash glass beer jug, ca. 1800 AD, Kunstsammlungen der Veste Coburg, (b) corrosion on lead-tin alloy.
Figure 3. (a) Potash glass beer jug, ca. 1800 AD, Kunstsammlungen der Veste Coburg, (b) corrosion on lead-tin alloy.
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Figure 4. Corrosion caused by a glass cabochon of the reliquary of the Saints Quirinus and Korbinian, around 1740, Parish Church Saint Quirinus, Tegernsee Abbey, No. 83W17632.
Figure 4. Corrosion caused by a glass cabochon of the reliquary of the Saints Quirinus and Korbinian, around 1740, Parish Church Saint Quirinus, Tegernsee Abbey, No. 83W17632.
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Figure 5. Detail of a hat pin, Museumslandschaft Hessen Kassel, Inv. Nr. MHK-Sch58b, with GIMME corrosion including ④.
Figure 5. Detail of a hat pin, Museumslandschaft Hessen Kassel, Inv. Nr. MHK-Sch58b, with GIMME corrosion including ④.
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Figure 6. Corrosion of a blue bowl with gilt brass base, mid-nineteenth century, Kunstsammlungen der Veste Coburg, acc. no. HA 557.
Figure 6. Corrosion of a blue bowl with gilt brass base, mid-nineteenth century, Kunstsammlungen der Veste Coburg, acc. no. HA 557.
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Figure 7. ⑥ on a gilded silver box with ruby glass, Green Vault Dresden IV169 (Photo: R. Richter).
Figure 7. ⑥ on a gilded silver box with ruby glass, Green Vault Dresden IV169 (Photo: R. Richter).
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Figure 8. (a) Pocket watch of the Museum für Hamburgische Geschichte, Inv. Nr. 1899.101b, (b) green ⑤ and white ⑦ corrosion.
Figure 8. (a) Pocket watch of the Museum für Hamburgische Geschichte, Inv. Nr. 1899.101b, (b) green ⑤ and white ⑦ corrosion.
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Figure 9. (a) Reagent tubes held by metal clamps to display plant remains in the Institute of Plant Biology Zurich; (b) corrosion on a metal clamp. (Photo: HE-Arc CR).
Figure 9. (a) Reagent tubes held by metal clamps to display plant remains in the Institute of Plant Biology Zurich; (b) corrosion on a metal clamp. (Photo: HE-Arc CR).
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Table
Table 1. GIMME Compounds.
Table 1. GIMME Compounds.
CompoundsFormulaRef.
Carbonates
① Sodium lead carbonate hydroxideNaPb2(CO3)2(OH)[18]
② Potassium lead carbonate hydroxideKPb2(CO3)2(OH)[19]
③ Sodium dicarbonato cuprate(II) trihydrateNa2[Cu(CO3)2]∙3H2O[20]
④ Sodium copper acetate carbonate hydrateNaCu(CH3COO)(CO3)∙nH2O[3]
Formates
⑤ Sodium copper formate hydroxide oxide tetrahydrateCu4Na4O(HCOO)8(OH)2∙4H2O[16]
⑥ Copper formate trihydroxideCu2(HCOO)(OH)3[3]
⑦ Zinc formate dihydrateZn(HCOO)2∙2H2O[21]
⑧ Zinc copper formate hydroxide hydrateZn4Cu3(Zn1–xCux)6(HCOO)8(OH)18·6H2O
0 ≤ x ≤ 1		[22]
Uncharacterised Compounds
Compounds containing Na, K, Cu, and/or Zn, often carboxylates[3]
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Eggert, G.; Fischer, A. Curious Corrosion Compounds Caused by Contact: A Review of Glass-Induced Metal Corrosion on Museum Exhibits (GIMME). Corros. Mater. Degrad. 2022, 3, 553-565. https://doi.org/10.3390/cmd3030030

AMA Style

Eggert G, Fischer A. Curious Corrosion Compounds Caused by Contact: A Review of Glass-Induced Metal Corrosion on Museum Exhibits (GIMME). Corrosion and Materials Degradation. 2022; 3(3):553-565. https://doi.org/10.3390/cmd3030030

Chicago/Turabian Style

Eggert, Gerhard, and Andrea Fischer. 2022. "Curious Corrosion Compounds Caused by Contact: A Review of Glass-Induced Metal Corrosion on Museum Exhibits (GIMME)" Corrosion and Materials Degradation 3, no. 3: 553-565. https://doi.org/10.3390/cmd3030030

APA Style

Eggert, G., & Fischer, A. (2022). Curious Corrosion Compounds Caused by Contact: A Review of Glass-Induced Metal Corrosion on Museum Exhibits (GIMME). Corrosion and Materials Degradation, 3(3), 553-565. https://doi.org/10.3390/cmd3030030

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