In-situ spectroelectrochemical studies of the removal of chlorides from copper

This paper describes corrosion potential measurements of corroded copper samples taken whilst acquiring timeresolved X-ray diffraction or X-ray absorption data in a synchrotron beam line. The surface structure of the samples and its evolution, whilst under simulated conservation treatment in sodium sesquicarbonate, were examined using X-ray diffraction. The fluid chemistry over the sample was monitored during identical experiments using X-ray absorption. All measurements were carried out with the sample immersed (i.e. without the need to expose the sample to air). Processes were followed from initial wetting of the surfaces through to the cessation of measurable change. A webcam was used to make a simultaneous visual record of the sample and its environment. The experiments aim at contributing to the improvement of conservation methods for cupreous artefacts recovered from marine environments

How to preserve lead artifacts for future generations

This paper discusses the advantages and disadvantages of different conservation treatments that have been developed over the years to protect the lead cultural heritage. The chemical and aesthetic points of view are looked at

A short historical overview on the use of lead

This historical introduction to the use of lead in art and technology was originally written to give context to lead conservation studies by the authors. The intention is to bring many rel- evant studies on lead together starting a discussion, which stresses that it was once impossi- ble to imagine a life without lead, and its alloys and compounds. Despite its environmental and health problems, lead remains ubiquitous even in modern technology for example in roofing, as an important component in low melting point or low friction alloys, in batteries and munitions

Electrochemical deposition of a copper carboxylate layer on copper as potential corrosion inhibitor

Carboxylic acids and sodium carboxylates are used to protect metals against aqueous and atmospheric corrosion. In this paper we describe the application of a layer of copper carboxylate on the surface of a copper electrode by means of cyclic voltammetry technique, and tests which measure the corresponding resistance to aqueous corrosion. Unlike the soaking process, which also forms a film on the surface, the use of cyclic voltammetry allows one to follow the deposition process of the copper carboxylates onto the electrode. The modified electrodes have been characterized with infrared spectroscopy. In addition the corrosion resistance of the film has been investigated using polarization resistance and Tafel plot measurements

In-situ time-resolved monitoring of copper corrosion using an automated electrochemical cell

A novel electrochemical cell has been designed for in-situ, time-resolved X-ray studies of corrosion and its inhibition on cultural heritage materials. Major aims are to monitor corrosion layers on alloys with realistic metallographic structures and surface roughness and to obtain co-incident electrochemical data, such as corrosion potential measurements, both with a time resolution in the range of seconds. This article reports on how a novel cell, to be used for monitoring the corrosion of copper, was tested

Optically detected X-ray absorption spectroscopy measurements as a means to monitor corrosion layers on copper

XANES and EXAFS information is conventionally measured in transmission through the energy-dependent absorption of X-rays or by observing X-ray fluorescence, but secondary fluorescence processes, such as the emission of electrons and optical photons (e.g., 200-1000 nm), can also be used as a carrier of the XAS signatures, providing complementary information such as improved surface specificity. Where the near-visible photons have a shorter range in a material, the data will be more surface specific. Moreover, optical radiation may escape more readily than X-rays through liquid in an environmental cell. Here, we describe a first test of optically detected X-ray absorption spectroscopy (ODXAS) for monitoring electrochemical treatments on copper-based alloys, for example, heritage metals. Artificially made corrosion products deposited on a copper substrate were analyzed in air and in a 1% (w/v) sodium sesquicarbonate solution to simulate typical conservation methods for copper-based objects recovered from marine environments. The measurements were made on stations 7.1 and 9.2 MF (SRS Daresbury, UK) using the mobile luminescence end station (MoLES), supplemented by XAS measurements taken on DUBBLE (BM26 A) at the ESRF. The ODXAS spectra usually contain fine structure similar to that of XAS spectra measured in X-ray fluorescence. Importantly, for the compounds examined, the ODXAS is significantly more surface specific, and > 98% characteristic of thin surface layers of 0.5-1.5-mu m thickness in cases where X-ray measurements are dominated by the substrate. However, EXAFS and XANES from broadband optical measurements are superimposed on a high background due to other optical emission modes. This produces statistical fluctuations up to double what would be expected from normal counting statistics because the data retain the absolute statistical fluctuation in the original raw count, while losing up to 70% of their magnitude when background is removed. The problem may be solved in future through optical filtering to isolate the information-containing band, combined with the use of higher input X-ray fluxes available on third-generation light sources

Towards a new method for coating heritage lead

Ethanolic solutions of long-chain carboxylic acids can be applied to lead metal substrates to form a coating of lead carboxylate which provides protection against atmospheric pollutants. In this paper we describe the optimal inhibitor concentration for the coating on lead. Electrochemical impedance data taken before and after immersion in media modelling oak emitted volatile organic compounds (VOCs) polluted atmospheres show that coating effectiveness decreases after exposure, but the effect is lessened if longer chain carboxylates are used