Rust Layers on Han Dynasty Coins with “Bright-Silver-Grey” Luster

Ultra-depth three-dimensional microscopy, scanning electron microscopy coupled with energy-dispersive X-ray analysis, X-ray fluorescence as well as X-ray diffraction were used to investiguate the corrosion products of ancient coins and soil on the surface of coins. The results revealed that the corrosion products mainly consisted of Cu₂S (silver-grey), Cu₂O (red), Cu₂(OH)₂CO₃ (green) and PbCO₃ (white). The mechanism of structure formation for the coins containing silver-grey corrosion products discussed.