Electrochemical Characterization of Corrosion Products in Leaded Bronze Sculptures Considering Ohmic Drop Effects on Tafel Analysis

A New Electrochemical Detection Technique for Organic Matter Content in Ecological Soils

The rapid detection of organic matter in soil is of great interest in agriculture, but the commonly used techniques require laboratory operation. Therefore, the development of a technique that allows rapid detection of soil organic matter in the field is of great interest. In this work, we propose an electrochemical-based approach for the detection of organic matter in soil particles. Since soil particles immobilized directly on the electrode surface can fall off during testing, we introduced graphene to coat the soil particles. The encapsulated soil particles can be stably immobilized on the electrode surface. We have investigated the electrochemical behavior of soil particles. The results show a correspondence between the electrochemical oxidation and reduction of soil particles and the organic matter content in them. We collected soil samples from three sites and constructed an electrochemical modeling, testing framework with stability based on multiple calibrations and random division of the prediction set. We used the equal interval partial least squares (EC-PLS) method for potential optimization to establish the equivalent model set. A joint model for the electrochemical analysis of organic matter in three locations of soil samples was developed for the commonality study.

Synchrotron-Based Phase Mapping in Corroded Metals: Insights from Early Copper-Base Artifacts

The detailed description of corrosion processes in ancient and historical metal artifacts currently relies on the in-depth study of prepared cross sections. The in-plane elemental and phase distributions can be established from a combination of light and electron microscopy characterization. Here, we show that high-resolution virtual sectioning through synchrotron X-ray microcomputed tomography allows a precise noninvasive 3D description of the distribution of both internal and external mineral phases in whole objects. In fragments of early copper artifacts (third-second millennium BC) from Southern Mesopotamia and the Indus valley, this approach provided essential clues on long-term corrosion processes. Major and minor phases were identified through semiquantitative evaluation of attenuation coefficients using polychromatic X-ray illumination. We found evidence for initially unidentified phases through statistical processing of images. We discuss interpretation of the distribution of these phases. A good correlation between the corrosion phases identified by CT and by invasive BSE-SEM is demonstrated. In addition to the stratigraphy of the copper corrosion compounds, we examine and discuss the variations observed in the attenuation coefficients of Cu(I) phases. Semiquantitative synchrotron X-ray microtomography phase mapping requires no specific sample preparation, in particular polishing or surface finishing, and any material tearing or displacement is avoided. We also provide evidence for the noninvasive observation of phases rapidly altered upon preparation of real cross sections. The method can be applied when cross-sectioning even of minute fragments is impossible.

Electroanalytical techniques in archaeological and art conservation

The application of electrochemical techniques for obtaining analytical information of interest in the fields of archaeometry, conservation and restoration of cultural heritage goods is reviewed. Focused on voltammetry of immobilised particles and electrochemical impedance spectroscopy techniques, electrochemical measurements offer valuable information for identifying and quantifying components, tracing provenances and manufacturing techniques and provide new tools for authentication and dating.

Archaeometric analysis of Roman bronze coins from the Magna Mater temple using solid-state voltammetry and electrochemical impedance spectroscopy

Voltammetry of microparticles (VMP) and electrochemical impedance spectroscopy (EIS) techniques, complemented by SEM-EDX and Raman spectroscopy, were applied to a set of 15 Roman bronze coins and one Tessera from the temple of Magna Mater (Rome, Italy). The archaeological site, dated back between the second half and the end of the 4th century A.D., presented a complicated stratigraphic context. Characteristic voltammetric patterns for cuprite and tenorite for sub-microsamples of the corrosion layers of the coins deposited onto graphite electrodes in contact with 0.10 M HClO₄ aqueous solution yielded a grouping of the coins into three main groups. This grouping was confirmed and refined using EIS experiments of the coins immersed in air-saturated mineral water using the reduction of dissolved oxygen as a redox probe. The electrochemical grouping of coins corroborated the complex stratigraphy of the archaeological site and, above all, the reuse of the coins during the later periods due to the economic issues related to the fall of the Roman Empire.