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1.
《文物保护研究》2013,58(2):125-134
AbstractA small but significant proportion of the archaeological iron objects in the British Museum collection have been problematic in that some of them have required repeated treatment. The deterioration of iron objects during storage was studied using microscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis, X-ray fluorescence spectroscopy and ion chromatography. A total of 125 iron objects, including 56 from two British Roman sites and 69 from three Anglo-Saxon sites, were studied. Both surface corrosion and corrosion layers on polished cross-sections were investigated. The study revealed that the present condition of the iron objects varies; some are in a stable condition and others have been deteriorating, with pitting and weeping present on the surface. No treatment method had stopped corrosion for every object, although the alkaline sulphite treatment seemed to be more effective than the other methods. The results also showed that chloride ions can be present at the interface of the metal and inner corrosion layers. It is recommended that iron objects which have been mechanically cleaned without desalination treatments are kept in a dry environment to prevent further deterioration. 相似文献
2.
《文物保护研究》2013,58(1):29-41
AbstractChloride-contaminated archaeological iron is unstable and problematic to store and display within museum collections. Reducing its chloride ion content using aqueous desalination followed by storage in controlled relative humidity offers one treatment option. This study reports a quantitative assessment of chloride extraction by aqueous deoxygenated alkaline desalination solutions from 120 individual archaeological iron nails. The three treatment methods comprised alkaline sulphite solution (0.1 M NaOH/0.05 M Na2SO3) at room temperature and at 60°C and sodium hydroxide solution (0.1 M) deoxygenated using a nitrogen gas positive pressure system at room temperature. Chloride extraction was monitored using a specific ion meter. The nails were digested after treatment to measure their residual chloride content. A wide range of extraction patterns emerged, with the majority of individual treatments extracting 60–99% of the chloride present. Residual chloride levels for 87% of the objects fell below 1000 ppm and 42% were below 200 ppm. Although no treatment extracted 100% of the chloride in the object, alkaline desalination produced very significant reductions in chloride content. The impact of this on future corrosion of the objects is discussed. This quantitative and statistically viable assessment of deoxygenated desalination treatments provides evidence to support their use in conservation practice, which will impact on procedures for the preservation and management of archaeological heritage. 相似文献
3.
《文物保护研究》2013,58(3):274-282
AbstractA study of the composition and phase distribution of the corrosion layers on three ferrous objects, excavated at K2 (Bambandyanalo), an archaeological site in South Africa, was conducted. The objective of the study was to obtain information that can contribute to conservation procedures to be performed on the iron artefacts from this site. Examination of cross sections by means of energy-dispersive X-ray spectroscopy coupled to a scanning electron microscope (SEM–EDX), X-ray powder diffraction (XRD), and micro-Raman spectroscopy revealed the same corrosion composition and structure for all the objects under study, namely an internal layer adjacent to the metal surface with ghost inclusions and an external layer containing quartz grains. The study also revealed that the presence of magnetite (Fe3O4), maghemite (γFe2O3), and lepidocrocite (γ-FeOOH) within the internal layer is the only difference between the chemical compositions of iron corrosion products within the two layers. The results also made it possible to retrace the corrosion history during burial and long-term storage. 相似文献
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《文物保护研究》2013,58(4):326-337
AbstractAlthough desalination of archaeological iron reduces its chloride concentration and enhances object stability, the reduction in corrosion rate that this produces has never been quantified. This study measures post-treatment corrosion rates in accelerated corrosion environments to identify the impact of removing chloride ions on corrosion rate. Thirty-five archaeological iron nails, treated individually in either alkaline sulphite or nitrogen-deoxygenated sodium hydroxide, were exposed to 75°C and 75% relative humidity together with 31 untreated objects from the same archaeological sites. Object weight change and visual examination of physical change before and after the test period were used to monitor corrosion. 77% of treated objects showed no weight gain and no visible signs of corrosion, while 90% of untreated objects did corrode. The impact of chloride on corrosion of untreated objects was clearly established by a significant linear correlation between chloride content and weight gain. Treated objects with <400 ppm chloride content showed no corrosion behaviour. Corrosion of treated objects was attributed to incomplete treatment: 93% of objects treated to <5 mg/l Cl? in the final solution bath displayed no corrosion behaviour. Based on these results, desalination of iron objects to enhance their stability offers a valuable option for reducing corrosion rates of archaeological iron, which should increase object lifespan. The results also raise the question of whether low levels of post-treatment residual chloride produce corrosion of any significance. Answering this will be an important step forward for managing the preservation of archaeological iron. 相似文献
5.
《文物保护研究》2013,58(3):155-171
AbstractThe presence of iron oxides (lepidocrocite, goethite) in archeological wood may result in a degradation of the wood matrix. Extraction of these iron oxides is largely dependent on their solubility. In this study, balsa wood samples were impregnated with iron oxides to test extraction treatments. Additionally, archeological wood samples were also examined to determine treatment efficiency. Electrophoresis and simple immersion treatments were performed using various chemical solutions: a neutral and a conductive substance (potassium nitrate), an acid (acetic acid), three alkaline chelating agents (tri-ammonium and tri-sodium citrate and sodium oxalate), three acidic and slightly acidic chelating agents (ethylenediaminetetraacetic acid (EDTA), citric acid, and oxalic acid), and a reductant (sodium dithionite). Potassium nitrate did not extract sufficient amounts of iron, irrespective of whether the treatment was conducted by electrophoresis or simple immersion; any observable dissolution was attributed to protonation because of the acidic pH around the anode (as low as 3). Dissolution in acetic acid did not extract iron with either treatment. Strong chelating agents improved extraction, and these compounds gave the best results for simple immersion, particularly EDTA. This chemical is well adapted for use on archeological objects because of its chemical properties (stability constant, speciation based on pH). The addition of sodium dithionite to the solution improved dissolution. Even though electrophoresis improved extraction (in particular for tri-ammonium citrate), none of the tested chelating chemicals were suitable for electrophoresis because of a significant increase in temperature as well as high anode corrosion. The presence of iron sulfide in the archeological wood limited the effectiveness of the tested chemicals. A pre-treatment in sodium persulfate was expanded to include oxidized iron sulfide in oxy/hydroxide iron, which improved the extraction rate. 相似文献
6.
AbstractThe use of sodium nitrite (NaNO2) as a corrosion inhibitor for wet archeological metal objects presents potential advantages of near neutral pH, low concentration, effectiveness on several metals, and compatibility with organic materials. The effectiveness of NaNO2 as a corrosion inhibitor for storage of chloride-containing marine archeological metal objects from the wreck of the USS Monitor was evaluated using marine-corroded carbon steel analogs. The samples were tested in varying concentrations of NaNO2 and evaluated visually and by monitoring solution chemistry using ion chromatography (IC). It was found that a concentration of 1000 ppm NaNO2, replaced four times, was effective at protecting corroded carbon steel in the presence of chlorides. Nitrite solutions were no more rapid than sodium hydroxide (NaOH) at extracting chlorides from marine steel at equal concentrations and were considerably slower than 2% NaOH. IC analyses indicated that NO2 does not easily oxidize to NO3 under normal conditions, but does so readily when a polarizing current is applied, making nitrites unsuitable for electrolytic reduction treatments. Sodium nitrite does show promise as a storage solution prior to desalination of marine metals or after desalination to prevent flash corrosion during rinsing baths. 相似文献
7.
AbstractThe long-term stabilization of marine archaeological iron, whether cast or wrought, continues to challenge conservators responsible for treatment of this material. Results and observations obtained from past treatments highlight the daunting, prolonged, and laborious efforts required to desalinate large and complex ferrous artifacts recovered from the ocean. In general, the higher an artifact's chloride level, the less stable it is. Consequently, any stabilization treatment must involve the removal of as much Cl?1 as possible without affecting the integrity of the corroded artifact. This problem is particularly acute with corroding cast iron objects that have formed thick, fragile, and highly unstable corrosion layers. Over the course of the twentieth century, conservators have used a variety of techniques in an attempt to mitigate the negative effects of chloride ions on iron artifacts and prevent disintegration. In spite of early promise, each of these stabilization techniques has significant disadvantages, particularly with regard to treatment efficiency, duration of treatment, and/or unacceptable risks to the artifact during treatment. For these reasons, conservators and conservation scientists at the Warren Lasch Conservation Center in Charleston, South Carolina, decided to look at the possibility of using subcritical fluids to stabilize archaeological iron. This paper compares the efficiency and effectiveness of traditional stabilization techniques (i.e. alkaline soaking and cathodic polarization) to subcritical fluids on wrought iron rivets and metal shavings from the H.L. Hunley submarine as well as Civil War era cast iron artillery shells recovered from a marine environment. 相似文献
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《文物保护研究》2013,58(3):179-190
AbstractTesting of chemical stabilization treatments and desiccated and anoxic storage microclimates for the protection of archaeological iron stored in unsuitable climatic conditions was carried out by the conservation department of the Japanese Institute of Anatolian Archaeology at the Kaman-Kalehöyük excavation in Turkey. The chemical stabilization treatments involved alkaline sulfite, barium hydroxide and sodium hydroxide. Environmental stabilization was explored using RP-A oxygen scavengers in Escal® bags as part of the Revolutionary Preservation System (RP System®) manufactured by Mitsubishi Gas Chemical Company, Inc. The efficiency of the chemical treatments was examined by comparison with mechanically cleaned iron objects. The efficiency of the storage systems was determined by comparing the chemically and non-chemically treated objects in the RP System® using RP-A scavengers and in polyethylene ziplock bags containing silica gel. The efficiency of these treatments and storage systems was examined and assessed at Kaman after a period ranging from 7 to 9 years. The anoxic and desiccating properties of the RP System® resulted in superior protective qualities over polyethylene bags with silica gel. The RP System® compensated for inadequate chemical stabilization and protected iron that had not been chemically stabilized. 相似文献
10.
《文物保护研究》2013,58(3):142-163
AbstractCorrosion noted on a number of nineteenth and twentieth century indoor bronze sculptures in the collection of the National Gallery of Canada was the cause for a major condition survey of its Canadian, American, and European bronzes. The results led to a comprehensive study, which included material analysis. This article outlines the steps undertaken to determine the extent and type of corrosion, its possible cause(s), and potential remediation. The survey included 136 bronzes, of which 40 were selected for an in-depth study. Indoor air quality tests of the current building, housing the collection since 1988, were carried out. The dossiers and database records of the selected sculptures were reviewed to investigate their condition, treatment, and storage history. The metal, patina, and corrosion products were subjected to analysis. More areas of corrosion were generally associated with predominantly green patinas and chloride-containing compounds identified in either patina or corrosion samples. The most frequently identified compounds in the patina samples were atacamite, a copper(II) chloride hydroxide, and cuprite, a copper(I) oxide. The most frequently identified compounds in the corrosion samples were atacamite and rouaite, a copper(II) hydroxide nitrate. The analysis determined that the current environment is not contributing to the surface alterations of the sculptures; however, past storage conditions, chemical residues from artificial patination, and likely casting residues are the main causes of the current condition. 相似文献
11.
ABSTRACTWe report on biological control of an active infestation by biscuit beetles (Stegobium paniceum) of museum objects (Old Masters paintings) in the storage facilities of the Museum of Fine Arts in Vienna. Because chemical and non-chemical treatment methods would have been very problematic, the release of parasitic wasps (Lariophagus distinguendus) was discussed and accepted by the director of the collection. We released 3000 wasps every month from August 2013 until September 2014 in the two infested storage rooms and monitored the activity of biscuit beetles on sticky blunder traps and light traps, and also by visual inspection. In the insect monitoring of 2014 until 2018 no more biscuit beetles were found in the two storage depositories, showing that the treatment was 100% successful. To our knowledge, this is the first proof of a fully successful biological control of a museum pest using parasitoids only, and also of stored product/food pest, outside a laboratory experimental setup. This biological pest control method allowed avoiding negative side effects such as contamination from treatments with biocides, or costly logistics in case of chemical-free methods. 相似文献
12.
SummaryThe rate at which chloride ions diffuse from archaeological iron into a treatment solution depends on how the chloride ions are initially distributed in the corrosion layer. This paper compares solutions of the diffusion equation for two limiting cases: (1) where the chloride ions are initially spread uniformly through the corrosion layer; and (2) where the chloride ions are initially concentrated at the interface between the iron and the corrosion layer. Although the first model has been used in the past to describe chloride ions diffusing from marine iron, the second is more appropriate in cases where corrosion has drawn chloride ions toward the iron surface. Because diffusion processes in archaeological iron are complicated, the limitations of both these models are discussed. 相似文献
13.
A technical study was conducted on a group of copper alloy artifacts excavated from the burial tumulus of Lofkënd (fourteenth–ninth century BCE) to identify the alloy compositions and methods of manufacture. The surface corrosion was also examined in order to understand the diagenetic processes affecting the preservation of the finds and their condition. Portable X-ray fluorescence spectroscopy, metallographic examination, and X-ray powder diffraction (XRD) analysis were used to characterize the alloy composition and identify the corrosion products present. XRD analysis showed the presence of brochantite (Cu4SO4(OH)6) on five of the metallic artifacts. Brochantite is not commonly reported on archaeological bronzes from terrestrial sites, but is more readily found on copper alloy objects exposed to sulfur pollutants in the air or soil. The possible conditions that could have led to the formation of this corrosion on the bronzes from Lofkënd are discussed in the context of the particular burial environment found at the tumulus. 相似文献
14.
ABSTRACTThis study examined the impact of relative humidity (RH) on the corrosion rate of 129 archaeological iron nails from two sites. Oxygen consumption of individual nails in controlled RH was used as a corrosion rate proxy to deliver quantitative data on corrosion rate as a function of RH. This was negligible at 20% RH, slow up to 40% RH for both sites, and increased rapidly at 60% RH for Roman nails from Caerleon (Wales) and at 70% RH for medieval nails from Billingsgate (London). The nails were digested and their chloride content was determined and related to their oxygen consumption at specific RH values. While a generic pattern of corrosion as a function of chloride was identified, for any single concentration of chloride corrosion rate was not predictable. Desiccation is in common use to control post-excavation corrosion of archaeological iron; quantifying how differing levels of desiccation changed corrosion rate provided a scaled tool for identifying corrosion risk, estimating object longevity, and calculating cost benefit for storage options. 相似文献
15.
《文物保护研究》2013,58(3):148-152
AbstractMineralogical changes which occur during the reaction of copper(II) chloride with carbonate in aqueous solution have been investigated, and compared with those involving copper(I) chloride, nantokite, CuCI, and copper artifacts coated with malachite, CU2CO3(OH)2 The reactions observed and the products obtained are seen to have implications with respect to the use of aqueous sodium carbonate solutions to stabilize archaeological copper objects. The frequent observation of the mineralogically rare species chalconatronite, Na2Cu(CO3)2·3H2O, on the surface of treated objects is readily explained by known reaction chemistry. Its formation can be minimized by washing the object after treatment. 相似文献
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《文物保护研究》2013,58(2):117-128
AbstractA system for continuous monitoring of atmospheric corrosivity has been developed. An electronic unit measures and records changes in the electrical resistance of a thin metal track applied on an insulating substrate. If the metal corrodes, the effective cross sectional area of the track decreases and the electrical resistance increases. Sensors made of silver, copper, iron/steel, zinc, lead, tin, aluminium, bronze, and brass at thicknesses from 50 nm to 250 µm were tailored for environments with different corrosivities. The developed technology proved capable of providing high sensitivity, allowing for real-time corrosion monitoring even in low-corrosive indoor cultural heritage facilities. Laboratory tests showed good reproducibility with the standard deviation of parallel measurements at less than ±20% for metals which corrode uniformly in the tested environments. Several examples selected from a broad testing programme in partner museums, libraries, and other institutions show successful applications of the logger system for characterization of air quality control in indoor locations, during transport and in temporary exhibitions; assessment of new buildings and storage facilities; and fundamental studies of optimal conservation and storage procedures. A first outline of a classification system for lead, which is particularly sensitive to the presence of carboxylic acids, is given. The technique has a large potential as an independent method for monitoring air quality in facilities displaying and storing valuable objects of cultural heritage. 相似文献
18.
《文物保护研究》2013,58(4):205-206
AbstractThe deterioration of Bronze Age objects from the archaeological site at Fort-Harrouard (France) has been studied, firstly, in relation to their external appearance and the elemental composition of the sound metal. A relationship between the composition of the corroded surface and the underlying sound metal was deduced. In addition, examination of metallographic sections of one of the bronzes allowed the differentiation of corrosion processes which are related to the shape of the object: the stratification of the corrosion products and the intergranular and transgranular corrosion processes. The existence of a pseudomorphic microstructure suggests that the mechanism of deterioration may be stratigraphic, which may be explained by the growth of the corrosion products in fissures which do not involve periodic precipitation. 相似文献
19.
ABSTRACTChalconatronite, Na2[Cu(CO3)]2·3H2O, is formed as a corrosion product when copper alloys are exposed to sodium carbonate solutions in the air. This also happens when metals come into contact with corroding soda glass which forms alkaline surface films in reaction with humidity from clean air. More often, substantial amounts of formaldehyde are present indoors which react to formate via the Cannizzarro reaction and accumulate over time in the films. Twenty cases of chalconatronite (including two mentioned in the literature) are reported as occurring on heritage objects with glass in contact with copper alloys: Baroque reliquaries with set glass gems, enamel on metal (sixteenth century and a modern replica of intentionally unstable composition), Christmas tree glass baubles with wires, glass buttons with metal shanks, a glass figure with a wire support, miners’ lamps, and a glass framed daguerreotype. These confirmed identifications might help conservators in investigating similar cases to shed more light on the formation conditions. 相似文献
20.
《文物保护研究》2013,58(3):136-142
AbstractVarious desalination methods had been used in the past to treat a large collection of archaeological iron objects. In order to establish whether desalination treatments had been effective, the condition of the objects was assessed and the data analyzed using statistical methods. It was found that objects which had been treated using desalination methods were less likely to re-corrode, and the conclusion was that the development of more effective techniques of chloride removal would be useful. 相似文献