Organic Acid Salt Corrosion Products of the Mahavairocana Buddha Statue

The unique rusting phenomenon on the surface of a Mahavairocana Buddha statue in the National Museum collection was scientifically analyzed using detection techniques such as X-ray fluorescence spectroscopy (XRF), optical video microscopy (OM), Raman spectroscopy, and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS). The results show that the material of the statue was copper zinc brass alloy, and the white crystalline substance covering multiple parts of its surface was sodium acetate trihydrate. The light blue rust products growing under the white crystalline salt layer were organic acid copper salts such as NaCu (CO₃)(CH₃CO₂), Cu₂(OH)₃HCOO. The research progress of related corrosion products was summarized. Sodium ions play an auxiliary role in the organic acid corrosion of copper cultural relics under alkaline conditions, and it is necessary to carry out surface desalination treatment for such cultural relics.