Influence of archaeological environment factors in alteration processes of copper alloy artifacts

Abstract

The article presents the experimental results obtained by combining noninvasive techniques (OM, SEM/EDX, XRF) to analyze three artifacts made of copper alloys discovered in a inhumation tomb (2) and in the soil profile (1) in archaeological sites from Neamt County Romania. To uncover the mechanism of alteration thereof during their longtime underground stay in specific chemical conditions and under the influence of other pedological factors, the corrosion products must be identified. The excess of the chloride ion, from burial site, disturbs the Liesegang effect, transforming the bulk in a stratified sponge structure with chlorapatite and hydroxyapatite. Some of the compounds from primary and secondary patina can be found on the surface of the bulk, as color stains. The presence of alloy components (Cu, Sn, Pb, Zn, Fe, etc.) and of the underground contamination components, allowed us to establish the origin of the ore, the manufacture technology and we identified other materials which affected the artifacts after abandonment.

Characterisation of copper alloy antique ornamental accessories found in Northern Albania

“…Corrosion on ancient objects is formed during the time of manufacture (primary patina), of usage in the atmosphere (secondary patina) and during the time of burial in soil or water (tertiary or contamination patina). Even (Vink, 1986;Domenech-Carbo et al, 2008;Pracejus, 2008;Sandu et al, 2008Sandu et al, , 2012Sandu et al, , 2014Domenech-Carbo et al, 2011;Mircea et al, 2012). Figure 4 shows the corrosion products of all objects with crossed nicols (polariser and analyser) polarised light (left) with reflected light (right).…”

Nondestructive Techniques in the Study of a Gilded Metallic Sword From the Islamic Art Museum

“…However, it is clear that the solubility of lead in copper is limited. The contact between silver and copper in the hilt of the sword enhanced the corrosion phenomenon whose main agent is the chloride anion coming from the surrounding environment, this induces the formation of silver and Cu (I) chlorides that could give rise to the copper cyclic reaction that continues to corrode copper when exposed to oxygen and humidity [21][22][23]. X-ray fluorescence analysis reveals the sword's body made of iron alloy.…”

Study on the Middle Bronze Age Disc-Butted Axe Ornament from Archaeometallurgical Point of View

“…It is a known fact that, both during their use and during their lying in the ground, ancient bronze artefacts suffered degradation effects (segregation of more active metals to the surface and change of chemical nature by surface corrosion processes), often accompanied, before abandonment, by thermal processes such as incineration or burning. They also suffered structural-functional deterioration effects, due to wear and pedological processes of erosion [15][16][17][18][19][20][21].…”

“…These allow the identification of archaeometric features used in authentication. Based on the composition, layout and shape of the structural components, the archaeometallurgical process of alloy obtaining and the manufacture of the artefact (hence of the ornament) may be assessed, and the routes travelled by the artefact from its commissioning to its discovery may be identified [20,21,23,24,27].…”

“…After the publication of recent research by the authors [3,[6][7][8][9][10]20,21,[36][37][38][39][40], a number of archaeologists commented on the ornament, that it was not an archaeo-pyrometallurgical process, but rather the Liesegang effect. (Of course, being not a specialist in chemistry or metallurgy, is hard to deepen either of the two processes).…”