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Metals used in dentistry in various forms such as metallic curative materials in the mouth, all metals may have the tendency to undergo tarnish or corrosion. The percentage of corrosion varying from metal to metal. Stainless steel and many other types of metal alloys are being used for the orthodontic treatment, which undergo chemical or electrochemical reaction with the oral environment. Here, polarization and alternating current impedance spectrums have been investigated for inhibiting corrosion of stainless steel in presence of fake saliva with and without green tea. Polarization investigation shows that the value of a linear polarization resistance is enhanced, the value of corrosion is decreased and the value of the alternating current impedance is increased by the amount of the CDL. Atomic force microscopic techniques reveals that the decrease in average roughness value on the stainless steel surface in artificial saliva + Green tea medium. The present survey shows that the persons cut with stainless steel orthodontic wire may drink oral green tea without concern.

The properties and glass-forming ability (GFA) of platinum- and palladium-based bulk metallic glasses (BMGs) for jewellery were introduced in Part I of this two-part review (1). Here, we will describe methods for their processing, tarnishing and corrosion resistance and consider their prospects and future developments.

We report a study on the effect of chemical and electrochemical cleaning of tarnished daguerreotypes observed using X-ray fluorescence (XRF) microscopy with a micro-focussed X-ray beam from a synchrotron source. It has been found that, while both techniques result in some success depending on the condition of the plate and the experimental parameters (chemical concentration, voltage, current, etc.) the effect varies, and cleaning is often incomplete. The XRF images using Hg Lα,β at an excitation energy just above the L3 edge threshold produce fine images, regardless of the treatment. This finding confirms previous observations that if the bulk of the image particles remains intact, the surface tarnish has little effect on the quality of the original daguerreotype image retrievable from XRF.

This study aims to develop chemical literacy instrument that can be used to measure chemical literacy skills of students. The chemical literacy instrument in this study was arranged based on four domains of chemical literacy consisting of content, context, HOLS and affective aspects. This study uses the Model of Educational Reconstruction (MER) design. Content validity testing was conducted with five experts and analysed using CVR, while empirical testing of students was analysed using the Rasch model with Ministep application. Based on results of this research, chemical literacy instrument on silver tarnish and silver polishing topic is categorized as valid and reliability value is of 0,92.

Tarnishing is one of the most crucial issues in the conservation of silver alloy objects. This phenomenon is relevant in the field of cultural heritage artifacts: although the blackish patina prote...

Polymer films have been used extensively to coat heritage metal objects to provide protection against atmospheric oxidation and tarnish. Coating performance is directly proportional to coating thic...

The appearance of silver objects deteriorates due to the formation of a brown-to-black tarnish layer. Several methods are available for removing these tarnished layers, ranging from polishing throu...

Among the main characteristics of silver and its alloys, tarnish resistance as well as surface brightness is essential. Alloying these materials with germanium has been shown to have considerable potential in providing tarnish protection. However, studies regarding the electrodeposited silver-germanium (Ag–Ge) alloy coatings are limited. The main objective of this study is to investigate the electrodeposition process of Ag-Ge alloy coatings with different Ge contents. In this regard, co-electrodeposition of Ag and Ge as an alloy coating was performed on pure copper substrates from a cyanide-based electrolyte. The effect of Ge incorporation on alloy composition, surface morphology, topography, texture, crystalline structure and cathodic efficiency of the obtained electrodeposits was investigated. Also corrosion properties of coatings were perused by polarization curves. Evaluation of the coatings was performed using different characterization techniques including XPS, SEM, FESEM, EDS, XRD, AFM, ICP, GIXRD, XRF, FTIR and electrochemical analysis. Results indicated that the optimum content of Ge in the coating was found to be 6 wt% regarding dense and uniform microstructure along with the best corrosion resistance. In addition, the X-ray diffraction patterns exhibited a shift in lattice parameter of Ag that was attributed to the Ag-Ge biphasic alloy formation. Moreover, the surface studies revealed a morphological transformation from nodular to cauliflower-like by increasing the Ge content of coating. The obtained polarization curves represent a remarkable decrease in Ag-6Ge alloy corrosion current density, about 20 times compared to Ag-0.5Ge and about 6 to pure silver. Discrepancies in characteristics between the Ag-Ge and pure Ag coatings were addressed and discussed.

In previous work, a monomolecular lubricant layer was applied on coin blanks by a burnishing process. With this layer, not only was the die life increased three times but the coin surfaces were pro...

Many conservators are reluctant to use silver dips based on thiourea because of reported problems such as yellowing and retarnishing as well as brown spots on daguerreotypes. Silver dips are report...

We report on atomic layer deposition (ALD) of Al2O3 films onto 925 silver and assess their efficiency to prevent metal scratching and tarnishing. Films of five thicknesses (12, 16, 21, 25 and 31 nm...

Silver and silver alloys usually tarnish, which causes some changes in their aesthetic appearance and electrical properties, due to their exposure to sulphide environments (H2S), and this is a problem in the field of corrosion and conservation of cultural heritage metallic artefacts. In this study, the role of copper content in the tarnishing process of 0.925, 0.800 and 0.720 silver alloys in a 0.07 vol.% ammonium sulphide solution for different immersion periods was analyzed by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The polarisation curves showed that the copper content and sulphide increased the corrosion current density and delayed the passivation of silver alloys. The impedance spectra collected at the open circuit potential (OCP) showed a single capacitive, incomplete and depressed loop, indicating that the charge transfer resistance decreased as the copper content increased in the alloys. In contrast, the double-layer capacitance increased as the copper content increased. The SEM−EDS analysis confirmed that the copper-rich phase in the silver alloys was selectively dissolved due to the preference of S to react with Cu, resulting in a localised attack, thus delaying the formation of a passive film. A marked localised attack was observed in alloys with lower copper content. The mechanism for the tarnishing of silver alloys in sulphide media was dependent on the nature of the alloy and the greater affinity of copper for sulphur. The dissolution of Ag and Cu to form corrosion products was proposed as the rate determining step.

A crisis can severely tarnish a company’s image and attempts to restore the damaged image may negatively affect postcrisis recruitment efforts. Because company image plays an important role in job seeker attraction, and company crises are on the rise, we examined the effects of postcrisis image restoration on job seeker attraction. We applied image restoration theory to a repeated-measures 2 (negative or neutral company information at Time 1) × 3 (two types of image restoration, and neutral for the same company at Time 2) factorial experimental design. We used the psychology of apologies to understand the underlying mechanisms by which a company’s image changes in the context of image restoration. Results showed that Time 2 ratings of image were more positive after restoration attempts; however, there was no significant difference between the two types of restoration or with the neutral condition. We also found that attraction to the organization assessed at Time 2 fully mediated the relationship between perceptions of image and intentions to pursue a job opportunity. The implications of our findings are that the valence of image restoration influences job seekers’ pursuant behavior more than what is said within image restoration.

Louis-Jacques-Mandé Daguerre introduced the first successful photographic process, the daguerreotype, in 1839. Tarnished regions on daguerreotypes supplied by the National Gallery of Canada were examined using scanning electron microscopy energy-dispersive X-ray spectroscopy and synchrotron-radiation analysis. Synchrotron X-ray fluorescence imaging visualized the distribution of sulfur and chlorine, two primary tarnish contributors, and showed that they were associated with the distribution of image particles on the surface. X-ray absorption near-edge structure spectroscopy determined the tarnish to be primarily composed of AgCl and Ag2S. Au2S, Au2SO4, HAuCl4 and HgSO4 were also observed to be minor contributors. Environmental contamination may be a source of these degradation compounds. Implications of these findings will be discussed.

Purpose To perform a comparative analysis of the microstructure, porosity, mechanical properties, corrosion, and tarnish resistance of Co–Cr alloys prepared by casting and three different computer aided designed/computer aided manufacturing (CAD/CAM) techniques. Methods Four groups of metallic specimens were prepared, one each by conventional casting (CST), milling (MIL), selective laser melting (SLM), and milling soft metal (MSM). Ten samples were tested by X-rays, after which their microstructure and elemental composition were tested by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Martens hardness (HM) and elastic index (ηIT) were determined by instrumented indentation testing (IIT), while modulus of elasticity (E) was determined by three-point bending. Corrosion measurements were tested according to International Organization for Standardization (ISO) 10271. The electrolytes were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results were analyzed by one-way ANOVA and Holm–Sidak’s multiple-comparison test (α = 0.05). Results The CST group illustrated internal flaws while all CAD/CAM group samples were found to be free of them. No statistically significant differences were identified among groups in their elemental composition. SLM showed the highest HM, followed by the MIL, CST, and MSM. Elastic index showed significant differences among all groups, with CST showing the lowest and SLM the highest values. SLM showed the highest elastic modulus values, followed by MSM, MIL, and CST. No significant differences were found in ionic release among groups. No surface deterioration after static and cyclic tarnish testing was determined. Conclusions The manufacturing procedure significantly affects the microstructure, porosity, and mechanical properties of Co–Cr alloys. In contrast, ionic release and tarnish resistance are independent of the manufacturing technique used.

Silver surface is prone for tarnish when exposed to sulfide and sulfate environments. Present work reports protection of silver surfaces with sol-gel derived mixed oxides of titanium-silicon (TiO2-SiO2) thin films prepared at room temperature (300K) by dip coating technique without any post annealing. 0.1M and 0.3M titania and silica individual sols are mixed in fixed volume to prepare 0.1M (TS1) and 0.3M (TS3) titania-silica mixed oxides. The corrosion measurements of the coated and un-coated silver surfaces have been evaluated by conventional electro-chemical measurements; alkaline Na2S and Na2SO4 are the electrolytes. The corrosion rates have been estimated from Tafel plots. The titania-silica protective thin films have shown significant decrease in the corrosion rates: bare silver from 1.06mmpy to protected silver surface 0.07mmpy. Ti-O-Si covalent bonds are revealed in Raman spectra of the mixed oxide films. The present investigation shows that sol-gel derived titania-silica films protect the silver surface from alkaline sulfide and sulfate environment very effectively.

One of the commonly used analytical approaches for measuring oxygen isotope ratios δ18O of solids (organic and inorganic) is to pyrolyze the samples to gaseous phases and then send the gas into an isotope ratio mass spectrometer system. Solid samples for δ18O measurements are usually stored in silver cups because of its low reactivity towards oxygen and other oxidants. Samples in silver cups can be dropped directly into the carbon column of the pyrolysis furnace. However, the silver cups can tarnish and then be oxidized over a prolonged storage period. We find that while a small amount of silver oxides does not affect measurements with appreciable sample sizes, it can skew isotope results of small samples. We thus recommend careful storage of samples in silver cups to minimize oxidation, such as under an air-isolated condition, and avoiding prolonged storage for accurate δ18O measurements.

This paper presents investigations of aluminum addition influence on the corrosion characteristics of the sterling silver Ag-Cu-Zn-Si alloys. The procedure for obtaining Ag-Cu-Zn-Al-Si alloys in small ranges of predefined composition was also presented. Open circuit potential measurements, linear polarization resistance method and potentiodynamic polarization tests were employed to determine corrosion characteristics of the alloys. The materials were tested in a 0.01M sodium sulfide solution. It was shown that the addition of aluminum improves sulfidization resistance and corrosion characteristics. Best results are achieved for the alloy with the following composition 92.5% Ag, 1.9% Cu, 3.7% Zn, 1.6% Al and 0.3% Si.

The influence of microstructure on anti-tarnish ability of silver deposit was studied by computational chemistry and experiments. The influence of microstructure on the anti-tarnish ability of silver deposit was firstly predicted by quantum chemical calculations. Theoretical studies revealed that high-index crystal surfaces of silver deposits were more sensitive to corrosive mediums and were seriously damaged when they were discolored. Based on the prediction of quantum chemical calculations, silver electrodeposition process with crystal surfaces controlled by additives was possible approach to improve the anti-tarnish ability of silver deposit in this work. The anti-tarnish ability of silver deposit influenced by crystal surfaces control was studied by surface discoloration investigation and Tafel plots measurements, as well as X-ray photoelectron spectroscopy (XPS) measurements. The results of these measurements confirmed the conclusions of theoretical studies; silver electrodeposition process with microstructure control can be used to improve the anti-tarnish ability of silver deposit.

To investigate the deterioration of textiles with metal thread, I surveyed 40 textile objects, dating from the 11th to the 19th century from Korea, China, Japan, and Central Asia at the Metropolitan Museum of Art, New York. This survey included various types, widths, and thicknesses of metal thread. In addition, deterioration was examined under the microscope and color information was collected using the spectrophotometer. While investigating metal thread in the collections, I fabricated 12 different types of metal samples with metal leaf(24K gold, silver, and copper leaf), adhesive (hide animal glue and a mixture of hide animal glue and iron oxide red), and paper substrate(Korean mulberry and Taiwanese kozo paper). The accelerated deterioration process of those fabricated samples was carried out using a light box(UV and daylight), and a humidity cabinet. In the light experiment with blue scales textile fading card(aka, blue wool standard), the metal leaf began to peel off during the deterioration process with 756,000 lux-hours UV and daylight. In the temperature and humidity experiment, I could observe the reddish tarnish on copper, and some part of it began to peel off. Color reading on the light exposed samples showed that the degree of color change on the surface follows the amount of exposure as it increased over time. On the other hand, color change on the samples after artificial deterioration using temperature and humidity factors showed random change of color with occasional spikes. Distortion of original shape worsened in the samples exposed to temperature and humidity.

We report the passivation of angle-independent plasmonic colors on bulk silver by atomic layer deposition (ALD) of thin films of aluminum oxide. The colors are rendered by silver nanoparticles produced by laser ablation and redeposition on silver. We then apply a two-step approach to aluminum oxide conformal film formation via ALD. In the first step, a low-density film is deposited at low temperature to preserve and pin the silver nanoparticles. In the second step, a second denser film is deposited at a higher temperature to provide tarnish protection. This approach successfully protects the silver and plasmonic colors against tarnishing, humidity, and temperature, as demonstrated by aggressive exposure trials. The processing time associated with deposition of the conformal passivation layers meets industry requirements, and the approach is compatible with mass manufacturing.

We report on the elemental and chemical characterization of tarnish on a historic daguerreotype plate. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy reveal the presence of C, O, Na, K, P, Cl, Hg, Ag, Cu, S and Au. Synchrotron based X-ray absorption near edge structure (XANES) spectroscopy, together with two-dimensional X-ray fluorescence (XRF) microscopy, provide information beyond the elemental distribution and speciation of the daguerreian tarnish features, revealing the presence of NaCl, KCl, HgCl2, HgSO4, CuS, and Ag2S on the surface. Through the application of synchrotron XRF, the distributions of Ag and S were found to be inversely correlated. This suggests a preferential accumulation of S within high-density particle regions. Spectroscopic investigation at different regions within the XRF image showed that blemish regions contained degradation products such as NaCl and KCl with AgCl noted in the surrounding regions. The observation of Cu on the surface, in the form of CuS, may either be a result of Cu diffusing through grain boundaries and/or holes in the Ag, or from the accretion of Cu salts, such as basic sodium copper carbonate, from the deterioration of the above cover glass. Silver halides (AgCl, AgBr and AgI) were also detected with XANES. This may be the result of either environmental conditions or from residual products from the production process of the plate. These results point to the interaction between deterioration products from the cover glass with the daguerreotype surface as one, but not the only, source of the tarnish.

Ancient silver artifacts become tarnished when they are exposed to sulfides (H2S) containing environments. As a result, a thin blackish layer is formed on the surface. In spite of the chemical composition, the tarnishing layer has the same color. Nowadays, there is a growing focus on research about tarnish in silver alloys, which allow us to understand its corrosion process, and support decision-making in conservation. However, previous works focused more on sterling silver and on the corrosion problems found on artifacts that are exhibited or stored. This paper studied the constituents of the tarnishing layer in the silver alloys, formed in a (NH4)2S solution, by electrochemical cathodic reduction and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). Ag2S and Cu2S were identified as the main constituents in this layer. SEM-EDS analysis showed a uniform distribution of Cu on the surface and higher weight loss as the copper content increases in the alloy.

Silver nanoparticles (Ag NPs) tarnish easily upon exposure to ambient air, and eventually lose their ability as a plasmonic sensor via weakened localized surface plasmon resonance (LSPR). We have demonstrated the enhancement in plasmonic sensitivity of tarnished Ag NP aggregates to vapors of volatile organic compounds (VOCs) such as ethanol and butanol by Ar plasma exposure. The response of Ag NP aggregates to the VOC vapors was examined by measuring the change in optical extinction spectra before and after exposure to the vapors. The sensitivity of Ag NP aggregates decreased gradually when stored in ambient air. The performance of tarnished Ag NPs for ethanol sensing was recovered by exposure to argon (Ar) plasma for 15 s. The reduction from oxidized Ag to metallic one was recognized, while morphological change was hardly noticeable after the plasma exposure. We conclude, therefore, that a compositional change rather than a morphological change occurred on Ag NP surfaces enhances the sensing ability of tarnished Ag NP aggregates to the VOC vapors.

Silver, as the most reactive noble metal, tarnishes immediately after exposure to industrial atmosphere or indoor S-bearing air. In this study, tarnish resisting and long term microstructural stability of silver-germanium (Ag-Ge) coating in industrial atmosphere is investigated and compared to silver electrodeposits. Ag-Ge coatings were electrodeposited on copper from cyanide base bath by DC current application. Coatings consisting about 0.5 to 6wt.% Ge have been studied and the optimum content of Ge in the coating was found to be 6 wt.% regarding dense and uniform microstructure along with best tarnish resistance and long term microstructural stability that has been discussed in this work. Ge forms a thin protective oxide layer, so a small incorporation of Ge in Ag structure, could improve tarnish resistance to a large extent. Tarnish resistance of samples have been evaluated according to ISO 4538 standard and considering color and reflectivity change detected by UV-Visible spectrometer. In addition, X-ray Diffraction (XRD) results were used to determine the crystalline structure of coatings before and after tarnish resistance and atmospheric corrosion. XRD patterns in grazing mode indicated the formation of Ge-Oxide passive layer on the Ag-6Ge surface which is known as the key factor for this sample's best performance. Scanning Electron Microscopy (SEM) along with Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy Dispersive Spectrometry (EDS) were used for microscopic analysis and surface characterization of samples. The various tarnish behavior of the coatings were evaluated and discussed via correlation to their microstructural characteristics in both severe and low aggressive conditions.

A plasma afterglow from a gas mixture of 5 vol% H2 in He is able to remove tarnish layers on pure silver in a matter of seconds. This dry, localized, and noncontact cleaning technique is a promising method to clean historical objects where silver is combined with organic materials and where traditional cleaning techniques are not recommended. However, historical objects are often manufactured with silver alloys but somehow their tarnish layers are removed less effectively with plasma treatments. To understand the different impact of the afterglow, the surfaces of corroded silver, sterling silver, and copper coupons are characterized before and after plasma treatment by a multianalytical approach combing optical and confocal microscopy, scanning electron microscopy coupled to energy dispersive X-ray analysis and chronopotentiometry. The analyses demonstrate that the few hundred nanometre-thick tarnish layer on pure silver is transformed through the whole thickness resulting in a porous metallic film. On top of that metallic film, some isolated remnant Ag2S particles are found. For sterling silver, a yellowing of the surface occurs. The Ag-rich corrosion products are reduced to a large extent, while the Cu-rich corrosion products are only partially reduced. For corroded copper, no apparent visual change is observed at a macroscopic scale, although the morphology of the surface changed. The results allow an evaluation of the cleaning efficiency and provide a deeper understanding of hydrogen plasma effects on the transformation of sulphide corrosion layers at atmospheric pressure.

Silver (Ag) objects tarnish when expose to the human sweat or atmospheres polluted by sulphide. In this work, a waterborne and transparent polyurethane/Ag (WPU/Ag) nanocomposite was synthesised and applied on the surface of the Ag sample with enhanced anti-bacterial and also protection against the tarnishing in the corrosive solutions. Ag nanoparticle in the WPU/Ag was investigated by field-emission scanning electron microscopy and transmission electron microscopy. To study the anti-tarnishing behaviour of the Ag samples, the bare as well as the coated samples were immersed in corrosion solution of 0.35 wt% Na 2 S which is a simulating solution of the human sweat. The corrosion products were then studied with X-ray diffraction and energy-dispersive X-ray spectroscopy. The bare Ag surface was covered completely by a black layer after 60 min immersion in the corrosion solution. However, the presence of either waterborne polyurethane (WPU) or WPU/Ag coatings was remained on the surface and protected the substrate from tarnishing. Anti-bacterial properties of the samples were determined by disc diffusion and the minimum inhibitory concentration methods. Anti-bacterial effect of the Ag coated by WPU/Ag was greater than the bare substrate, whereas the WPU coating lost the anti-bacterial effect of the Ag substrate.

Sterling alloy is widely used in the jewelry industry. Its anti-tarnish property is one of its most important characteristics. In this study, the effect of tin on the corrosion resistance, and tarnish resistance properties of sterling silver alloy were investigated quantized. The difference between anti-corrosion and anti-tarnish properties was investigated in this paper. The tarnish and corrosion resistance of sterling silver improved as tin content increased. However, there was a point at which increasing tin content further led to poor anti-tarnish properties, even though the alloy retained considerable anti-corrosive properties.