PVA Composite Hydrogel Film for Rust Removal of an Ancient Chinese Fragile Bronze Artifact.

In heritage conservation, bronze artifacts are highly valued for their unique historical and cultural significance. However, due to the complex environmental factors and the long erosion of time, many bronze artifacts commonly face more severe rust issues, directly leading to fragility and even damage. Traditional rust removal methods often failed to effectively eliminate corrosion of fragile bronze artifacts and may cause irreversible damage, particularly for the delicate bronze artifacts with complicated surfaces. Therefore, there is an urgent need to explore milder and more efficient rust removal techniques for fragile bronze artifacts. This work reports a composite hydrogel film composed of poly(vinyl alcohol) (PVA) hydrogel and the chelating agent ethylenediaminetetraacetic acid (EDTA) based on a solvent-exchange method, which is further applied to remove copper rust from fragile bronze antiquities via surface attachment, hydrogel film formation, and the peel off process. EDTA reacts with metal oxides during the hydrogel film formation process. The copper rust was then removed from the surface of the artifact along with the hydrogel film. The PVA composite hydrogel film is further peeled off from the surface of fragile bronze antiquities due to its good toughness, effectively removing copper rust. The fabricated PVA composite hydrogel film was tested to clean a fragile bronze artifact excavated from Shaanxi Province in China, which can remove ∼90% of the copper rust from the surface. This indicates the effectiveness and feasibility of the PVA-based hydrogel film in the restoration and protection of fragile bronze artifacts.