In recent years, 3D technology has been widely used in various aspects of the entire workflow of conservation–restoration. However, in the majority of cases, researchers have mainly relied on 3D technologies to assist the conventional conservation–restoration process, and its advantages have not truly been exploited. In this paper, we applied a combination of digital acquisition, virtual anastylosis, virtual reconstruction, and 3D printing of a transparent reversible prosthesis with slots for the restoration of a gold foil decorated Black Ding bowl collected by the Chifeng Museum of the Inner Mongolia Autonomous Region. While completing the physical/aesthetic restoration of the artifact, the conservation–restoration principles of the integrity and authenticity of cultural heritage, minimal intervention and reversibility were followed to the utmost extent. At the same time, we also conducted preliminary performance tests on the 3D printing material of the prosthesis, and the results showed that the material has excellent mechanical properties and stain resistance, contributing to the long-term, stable preservation of the artifact. This work presents an innovative solution applicable to other pieces of cultural heritage and has high significance for promotion.

A large number of iron pot artifacts were excavated from the “Nanhai I” shipwreck. The rapid embrittlement and pulverization of these objects (that have a good matrix) in the atmospheric environment is worthy of attention. Metallographic analysis showed that the material of the iron pots was hypereutectic white cast iron. Micro-CT observations revealed that there were numerous microcracks and fissures within the seemingly well-preserved iron. These fissures increased and enlarged with prolonged exposure to air. Scanning electron microscopy exhibited that the microcracks were initially created at the “concave surface” formed by the ferrite corrosion, and the cementite was gradually torn by the local accumulation of large internal stresses. Micro-Raman proved that the structure of rust was varied and complex during the generation and development of fissures. The dimension of corrosion products could expand and contract in mutual transformation, forming local internal stress and promoting the expansion of microcracks. This work proposed a reasonable mechanism for the rapid embrittlement and pulverization in the atmospheric environment of such hypereutectic white cast iron artifacts out of the sea, which provided a scientific reference for future protection.

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.

Ancient iron artifacts need to be protected with a rust layer, often stabilized by tannic acid corrosion inhibition. In humid environments, water vapor could slowly penetrate and trigger galvanic corrosion of metal artefacts. Sealing treatments are generally applied to the artefact surface to isolate water and enhance its corrosion resistance. Superhydrophobic modifications could effectively block the penetration of moisture into the interior of the artefact and provide a nice water barrier. Stearic acid with tannic acid inhibition treatment creates a superhydrophobic protective layer on the surface of rusted iron artifacts and enhances corrosion resistance effectively. Various scientific analyses and testing methods are used in this paper to evaluate the corrosion resistance of rusted surfaces after superhydrophobic modification and investigate the reaction mechanisms. The results indicate that the contact angle of the rusted surface after corrosion inhibition by tannic acid and modified by stearic acid is increased to 152.2°, which means the superhydrophobic protective layer has been successfully constructed. The C/Fe ratio of the rusted surface is increased from 0.21 to 2.10, and the characteristic diffraction peaks of O1s and Fe 2p_3/2 shift toward higher binding energy. Stearic acid is combined with the corrosion product layer by chemical bonding. Chelation between rust products, tannic acid, and steric acid is effective, and the chelate is chemically stable. The superhydrophobic surface forms a lamellar wax-like layer as an air barrier to isolate liquid water, resulting in a significant decrease in corrosion current and an increase in Warburg impedance to 217.9 times the original state, with a protection efficiency of 88.3%. Tannic acid corrosion inhibition and stearic acid superhydrophobic modification have an excellent synergistic protective effect on improving the corrosion resistance of iron artifacts, resulting in better corrosion resistance of iron artifact materials. The research provides new ideas and references for the protection of ancient iron artifacts sealing.

Archaeological silver artifacts are often found to be brittle because of long-term corrosion. However, the restoration of brittle archaeological silver artifacts by thermal treatment has never been quantitatively and systematically studied due to the lack of sufficient experimental samples. Herein, the simulated Ag–Cu alloy flake samples with intergranular corrosion consistent with those brittle archaeological silver artifacts were prepared through two-step annealing and accelerated aging in Fe(NO₃)₃ + AgNO₃ solution. The changes in the microstructure and mechanical strength (σ_bb, E_b, and HV) of the brittle samples after thermal treatments were studied with the help of SEM–EDS, metallographic observation, three-point bending tests, and microhardness tests. In addition, the most suitable conditions for the restoration of the brittle samples were summarized by the temperature–time (T-t) map obtained from a series of comprehensive thermal treatments. Moreover, the differences in microstructures and mechanical strength between the brittle samples annealed in an aerobic/anaerobic environment were revealed. This work provides an important reference for the restoration and conservation of brittle archaeological silver artifacts.

In recent years, with the excavation of an increasing amount of gold and silver artifacts, there has been an urgent need to optimize the formulations and methods of metallographic etching. Herein, a kinetic control study is performed to investigate the mechanisms leading to poor results when etching ancient gold materials with aqua regia, i.e., when secondary AgCl impurities form during the etching of the sample surface. To this end, a concentrated ammonia and sodium thiosulfate solution is used to dissolve AgCl impurities and obtain high-quality metallographic images of ancient gold materials using a coordination reaction to generate stable free-state coordination ions from Ag⁺. On this basis, a ferric chloride + sodium thiosulfate method is proposed to optimize the formulation of the etchant for ancient silver materials. The formulation is efficient, safe and easy to handle, and solves the problems of the easy failure of the commonly used etchant of ammonia + hydrogen peroxide and the complicated preparation process of acidified potassium dichromate while maintaining the long-term stability of the etched Ag–Cu alloy samples.