Microstructure and phase composition of bronze Montefortino helmets discovered Mediterranean seabed to explain an unusual corrosion

Microstructure and Chlorine Ion Corrosion Performance in Bronze Earring Relics

Chlorine ions play an important role in the corrosion of bronzeware. This study employs techniques such as XRD, OM, SEM, EBSD, and electrochemical testing to analyze the microstructure, crystal structure, chemical composition, and corrosion performance of bronze earrings unearthed at the Xindianzi site in Inner Mongolia. The results indicate the presence of work-hardened structures, including twinning and equiaxed crystals, on the earrings' surface. With an increase in chloride ion concentration in NaCl solutions from 10-3 mol/L to 1 mol/L, the corrosion current density of the bronze earrings increased from 2.372 × 10-7 A/cm2 to 9.051 × 10-7 A/cm2, demonstrating that the alloy's corrosion rate escalates with chloride ion concentration. A 3-day immersion test in 0.5% NaCl solution showed the formation of a passivation layer of metal oxides on the earrings' surface. These findings underscore the significance of the impact chloride ions have on the corrosion of copper alloys, suggesting that activating the alloy's reactive responses can accelerate the corrosion process and provide essential insights into the corrosion mechanisms of bronze artifacts in chloride-containing environments.

Early Stages of Metal Corrosion in Coastal Archaeological Sites: Effects of Chemical Composition in Silver and Copper Alloys

In this study, metal disks with different chemical composition (two Ag-based alloys and three Cu-based alloys) were buried in the soil of coastal archaeological sites for a period of 15 years. The aim was to naturally induce the growth of corrosion patinas to obtain a deeper insight into the role of alloying elements in the formation of the patinas and into the degradation mechanisms occurring in the very early stages of burial. To reach the aim, the morphological, compositional and structural features of the patinas grown over 15 years were extensively characterized by optical microscopy, field emission scanning electron microscopy coupled with energy dispersive spectrometry, X-ray diffraction and micro-Raman spectroscopy. Results showed that the Cu amount in Ag-based alloys strongly affected the final appearance, as well as the composition and structure of the patinas. Corrosion mechanisms typical of archaeological finds, such as the selective dissolution of Cu, Pb and Zn and internal oxidation of Sn, occurred in the Cu-based alloys, even if areas enriched in Zn and Pb compounds were also detected and attributed to an early stage of degradation. In addition, some unusual and rare compounds were detected in the patinas developed on the Cu-based disks.

Conversion of archeological iron rust employing coconut husk lignin

Rust powder collected from an archeological iron was evaluated by complementary analyses such as FTIR, XRD, XRF, and SEM/EDX. The analyses revealed that lepidocrocite (L) was the major component in the archeological iron. Coconut husk (CH) can be classified as a type of lignocellulosic biomass of renewable resources that are widely available, especially in coastal areas. In this research, the isolated lignin extracted from CH is being studied as a potential alternative for environmentally friendly applications. The isolated lignin from soda and organosolv pulping went through several analyses such as FTIR, NMR (13C and 2D-HSQC), and TGA analyses. The analyses showed that lignin isolated via soda pulping has superior antioxidant capabilities due to its greater phenolic-OH content compared to lignin isolated from organosolv pulping. The effects of lignin concentrations, pH, and reaction time were utilized in rust conversion studies of an archeological iron. 5 wt% of soda lignin (SL) was revealed as the ideal condition in this rust conversion study with a value of 84.21 %. The treated rust powder with 5 wt% of SL was then further gone through several complementary analyses, which revealed that the treated rust had nearly transformed into an amorphous state.

The Corrosion Properties of Bronze Alloys in NaCl Solutions

Chloride ions play an important role in the corrosion of bronze through their active reactivity to copper alloys. The corrosion behavior of bronze alloys in NaCl solution was investigated by using X-ray diffraction (XRD), a scanning electron microscope (SEM), and electrochemical tests, with a special emphasis on the corrosion resistance of the α and δ phases in Cu-20 wt%Sn bronze alloys. The experimental results show that the corrosion current density of Cu-20 wt%Sn bronze alloys increases from 1.1 × 10^-7 A/cm² to 2.7 × 10^-6 A/cm² with the increase in the chloride ion concentration from 10^-3 mol/L to 1 mol/L. After a soaking duration of 30 days, the matrix corrosion depth reaches 50 μm. The α phase of the alloys is easily corroded in NaCl solution, while the δ phase with high Sn content has strong corrosion resistance. This study provides relevant data for the analysis and protection of ancient bronze alloys.

From Collection or Archaeological Finds? A Non-Destructive Analytical Approach to Distinguish between Two Sets of Bronze Coins of the Roman Empire

This study stems from the need for numismatics to establish whether there may be relationships between a group of 103 bronze coins from the Roman era found in archaeological excavations on the Cesén Mountain (Treviso, Italy) and a group of 117 coins kept at the Museum of Natural History and Archaeology in Montebelluna (Treviso, Italy). The chemists were delivered six coins with neither pre-agreements nor further information on the origin of the coins. Therefore, the request was to hypothetically assign the coins to the two groups on the basis of similarities and differences in their surface composition. Only non-destructive analytical techniques were allowed to be used to characterize the surface of the six coins taken blindly from the two sets. The elemental analysis of each coins' surface was carried out by µ-XRF. To better observe the morphology of the coins' surfaces, SEM-EDS was used. Compounds covering the coins coming from both corrosion processes (patinas) and the deposition of soil encrustations were also analyzed by means of the FTIR-ATR technique. The molecular analysis confirmed the presence of silico-aluminate minerals on some coins, unequivocally indicating a provenance from clayey soil. Some soil samples, collected from the archaeological site of interest, were analyzed to verify whether the encrusted layer on coins could contain chemical components compatible with them. This result, together with the chemical and morphological investigations, led us to subdivide the six target coins into two groups. The first group is made up of two coins coming from the set of coins from excavation (found in the subsoil) and from the set from open air finds (coins found in the top layer of the soil). The second group is made up of four coins that are devoid of characteristics corresponding to exposure to soil contact for long periods of time and, moreover, their surface compounds could suggest a different provenance. The analytical results of this study made it possible to correctly assign all six coins to the two groups of finds and support numismatics, which was unconvinced in considering all coins to come from the same finding site only on the basis of archaeological documentations.

New Insight on Archaeological Metal Finds, Nails and Lead Sheathings of the Punic Ship from Battle of the Egadi Islands

The wreck of the Punic ship exhibited at the Archaeological Park of Lilybaeum (Marsala, Italy) is a unique example in the world. In this paper, the investigation of some metal finds (30 nails and 3 fragments of sheathings) belonging to the wreck of the Punic ship is reported. Portable X-ray fluorescence and Raman spectroscopy allowed us to identify the elements and compounds constituting them and make some deductions about their composition. X-ray diffractometry, polarised optical microscopy and scanning electron microscopy of the collected micro-samples allowed us to explain the degradation that occurred in the underwater environment.

Corrosion Inhibition and Rust Conversion of Catechin on Archaeological Iron of Nanhai I

This work took the iron objects from the Nanhai No. 1 shipwreck in the Southern Song Dynasty of China as the sample to test and analyze the application potential of catechin, an environmentally friendly corrosion inhibitor and rust converter. The article used metallographic microscopy to clarify that the structure of the iron artifact was hypereutectic white iron. By means of micro-Raman, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy, catechin had the ability to react with iron oxyhydroxides such as goethite, akaganeite and lepidocrocite in the rust, forming an amorphous substance with a marked signal about 1380 cm−1 as phenolic-Fe in infrared properties. The new products could make the original rust layer form a laminated dense structure. After the archaeological iron was soaked in 3.0 g/L catechin, the corrosion current density decreased by 37.13% and the corrosion potential shifted positively by 32.67 mV. The anode reaction was more inhibited than the cathode in the polarization curve. The rust resistance in electrochemical impedance increased to 3.75 times and the ion diffusion resistance increased to 6.33 times. The corrosion inhibition efficiency was 21.75% and the rust conversion efficiency was 73.26%. After 36 h of accelerated corrosion, the protection effect of the newly transformed rust layer was still better than that of the original state. Catechin was a mild protection material which showed satisfactory performance for archaeological iron and has a good application prospect.