Structural Characteristics and Classification of Patina on Ancient Bronzes

Statistical analysis is carried out on the bronze rust layer research in the past 20 years, and according to their composition and structure,the ancient rust layer profile samples are divided into four basic types: chlorine-containing rust layer (Type Ⅰ), oxide rust layer (Type Ⅱ), hydrated rust layer (Type Ⅲ) and tin-rich rust layer (Type Ⅳ). On this basis, a large number of representative rust layers are used as standard rust layers, and the rest are regarded as derived rust layers. The diversity of rust layer types is related to the ion content and diffusion process in the environment. The process of chloride ions acting on the metal matrix in the environment is an important factor affecting the formation of the cuprous chloride layer. The content of other anions and oxygen in the environment directly affects the generation and transformation of oxidation products and their secondary corrosion products. In this process, the diffusion process of ions directly controls the deposition and stratification of corrosion products, forming a rust layer with variable structure.