Unexpected Damage on Metal Artifacts Triggered by the Hazardous Interfacial Interaction from Aging of Polymer Coatings

Polymer coatings are currently being employed for preservation of metal artifacts. However, there is insufficient awareness that inevitable aging of polymer coatings is bound to damage metal artifacts due to the lack of a direct and sensitive methodology to study the aging behaviors of polymers coated on the artifacts. Herein, we have developed an in situ and three-dimensional strategy to visualize the early stage aging behaviors of polymers coated on metal artifacts by lighting carboxyl groups generated from polymer aging. It is disclosed that polymer aging occurred simultaneously at the surface and the interface with metal artifacts, generating carboxyl groups and hydroxyl radicals to induce the corrosion and oxidation of metallic artifacts. In turn, the generated metallic ions could further aggravate the aging of polymer coatings, manifested as the larger volume of the aged sites at the interface with metal artifacts in comparison with that at the surface of polymer coatings. Such a circular reaction is validated using real metal artifact samples. These findings raised a timely alarm for the conservation ability and potential threat of polymer coatings on metal artifacts. It is anticipated that the proposed strategy could provide solid supports for the implementation of advanced conservation strategies for metal artifacts.