Electrochemical Characterization of Archaeological Tin‐Opacified Lead‐Alkali Glazes and Their Corrosion Processes

Abstract

The electrochemical response of weathered and unweathered archaeological tin-opacified glazes attached to paraffinimpregnated graphite electrodes is described. Upon comparison with the square wave voltammetric response of SnO 2 , PbO and PbO 2 , Sn-and Pb-centered reduction processes can be characterized. Reduction of Sn(IV) involves the stepwise formation of solid Sn(II) and Sn metal, successively, at potentials of À 0.08 and À 0.55 V vs. AgCl/Ag. Reduction of network-modifier Pb(II) in glazes occurs at À 0.5 V and is accompanied by the reduction of networkforming Pb(IV) at potentials ranging from þ 0.65 to þ 0.20 V, confirming the presence of such centers in glazes. Voltammetric data suggest the presence of small amounts of Sn(II) resulting from the reduction of cassiterite during the firing process. A series of correlations between the peak currents can be established, indicating that the weathering process obeys a kinetic process rather than a equilibrium-like situation.

Electrochemical Detection of High Oxidation States of Chromium(IV and V) in Chromium‐Doped Cassiterite and Tin‐Sphene Ceramic Pigmenting Systems

“…The response of M-5 was similar, but here a prominent cathodic current appears at -0.55 V, while in the subsequent anodic scan a well-defined tall peak at -0.50 V is recorded. This corresponds, as described in detail elsewhere, [18] to the stripping oxidation of Sn to Sn 2+ in solution, thus denoting that the prior cathodic step results in the formation of a deposit of Sn metal. In the positive region of potentials, a weak anodic peak near +0.5 V is also recorded.…”

“…[17] This scheme has previously been applied for studying the electrochemistry of SnO 2 and Sn-rich glazed ceramics. [18] Studies on nanosized SnO 2 particles dispersed on graphite electrodes, [19] nanocrystalline tin oxide electrodes [20] and modification of the film of SnO 2 nanocrystallites with organic reagents, [21] all devoted to the detection of selected analytes, have also been reported. The electrochemical dissolution of chromium oxides, spinels, and chromites has been studied by Blesa et al [22][23][24] and Grygar et al [25][26][27] Other reports on the solid-state electrochemistry of chromium concern chromium(ii), hexacyanochromate(iii), [28] some organic Cr complexes [29] and chromium oxide films deposited on stainless steel.…”

Electroanalytical chemistry for the analysis of solids: Characterization and classification (IUPAC Technical Report)

“…The relative quantification of the species in two different oxidation states can be performed based on voltammetric data, under several favourable conditions, from the measurement of different electrochemical parameters [149,187]. This possibility is illustrated by the estimate of the Fe(III)/Fe(II) ratio in ceramic materials [149], and the identification/quantification of different lead and tin species [188] in archaeological glazed materials and speciation of manganese in carbonates and marine sediments [189,190] have been also reported. Speciation involves also isomer discrimination, as is the case of cis-and trans-Cr(CO) 2 (dpe) 2 and trans-[Cr(CO) 2 (dpe) 2 ] + complexes (dpe = Ph 2 PCH 2 CH 2 PDh 2 ) [191,192].…”

Electrochemical analysis of metallic heritage artefacts: voltammetry of microparticles (VMP)

“…Synergistic combination of VMP with suitable non-electrochemical techniques, namely, microscopy (optical microscopy, scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDX), transmission electron microscopy (TEM)), diffraction (mainly X-ray diffraction (XRD)), and spectroscopy (typically, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray fl uorescence (XRF)), can provide relevant analytical information for archaeometry, conservation and restoration, as described in recent reviews [30][31][32]. In particular, VMP has been used for analysing inorganic [33] and organic [34] pigments, ceramic [35], glass [36] and glazed [37] materials, textiles [38] and hybrid organic-inorganic archaeological materials [39][40][41][42].…”