Corrosion products of organic acid salts from the bronze mirrors in the Qingdao Museum

Corrosion products of organic salts on the surfaces of cultural heritage artifacts are commonly found in the form of metal formates and acetates. These compounds can persist and exacerbate corrosion, particularly in enclosed display or storage environments, thereby posing a significant threat to the long -term stability of these objects. The Qingdao Museum houses a substantial collection of historically valuable bronze artifacts. In recent years, blue green corrosion products have been observed on the surfaces of several bronze mirrors; however, their precise composition and formation mechanisms remain poorly understood. This study employs a series of analytical techniques, including scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), confocal raman spectroscopy, fourier transform infrared spectroscopy (FT−IR), and X-ray diffraction (XRD), to characterize the phase composition of these corrosion products. The results reveal a microstructure composed of white crystals and layered, plate-like blue green crystals. The major identified compounds include sodium acetate trihydrate [Na (CH₃COO)·3H₂O], chloride-containing sodium copper carbonate acetate [NaCu (CO₃) (CH₃COO)], and basic copper formate [Cu₂ (OH)₃ (HCOO)]. These findings not only provide a new case study of the formation of organic acid-induced corrosion in bronze artifacts but also offer a scientific basis for optimizing environmental conditions for the preservation of metal heritage materials in museums.