ЦИФРОВА РЕКОНСТРУКЦІЯ КОРОЗІЙНИХ ФАЗ МІДІ ТА БРОНЗИ ЯК ІНСТРУМЕНТ ДІАГНОСТИКИ ТА ІНТЕРПРЕТАЦІЇ ПАТИН
DIGITAL RECONSTRUCTION OF COPPER AND BRONZE CORROSION PHASES AS A TOOL FOR DIAGNOSIS AND INTERPRETATION OF PATINAS

Summary/Abstract: Research Aim: The aim of the study is a comprehensive investigation of the chemical aging processes on model copper and bronze coins from different historical periods, followed by structural modeling of Cu (II) coordination compounds and digital reconstruction of corrosion phases using the VESTA software environment. Special emphasis is placed on establishing correlations between the local atomic structure of Cu (II) coordination polyhedra and the macroscopic characteristics of patinas, including their color, texture, optical parameters, and stability. The proposed approach is aimed at developing a methodology for comparing model and naturally formed corrosion systems, assessing the preservation of real patina layers, and expanding the possibilities of digital structural analysis in numismatics, archaeometry, and conservation practice. Research Methodology: The study was conducted on prepared model samples of technically pure copper simulating coin artifacts, as well as real samples of historical bronze coins. Exposure conditions typical for archaeological and museum objects were simulated, including bicarbonate, atmospheric-humidity, chloride-containing, and combined environments. The development of corrosion products was monitored using optical observation with digital photography and quantitative color assessment in the Munsell and CIELAB systems. To establish the relationship between atomic structure and macroscopic manifestations of patinas, digital modeling of key phases (malachite, cuprite, atacamite, etc.) was performed using VESTA, based on data from the Crystallography Open Database. Scientific Novelty: The novelty of the study lies in the combination of experimental observation of corrosion processes with digital crystallochemical reconstruction, enabling the prediction of patina morphology and stability based on the geometry of Cu (II) coordination polyhedra. For the first time, a methodological approach integrating structural modeling, quantitative color assessment, and observation of corrosion film behavior is proposed, forming a basis for standardized digital description of corrosion phases in coins and artifacts. Conclusions: Patina stability is a complex characteristic determined by the combination of alloy composition, presence of barrier phases (notably SnO2), the degree of primary corrosion degradation, and environmental influence, and can serve as a reliable marker of coin authenticity. Chloride phases are the least stable and most fragile, posing a threat to coin preservation and potentially indicating artificial intervention, whereas cuprite and malachite films form dense, predictable structures characteristic of natural aging. Comparative patination allows the identification of individual corrosion scenarios for each historical specimen and demonstrates that even under identical exposure conditions, coins of different composition or origin may react significantly differently, which is important for distinguishing originals from counterfeits. Digital crystallochemical modeling, such as in VESTA, effectively refines the phase nature of corrosion products and provides structurally justified criteria for authentic patina identification, allowing differentiation from artificially applied layers. The results also provide a foundation for the development of standardized digital databases of patinas and corrosion phases, significantly enhancing the accuracy of attribution, diagnostics, and conservation assessment of numismatic artifacts, and effectively counteracting forgeries.

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