Corrosion Situation of Copper Coins from Shipwreck Huaguang Reef No. Ⅰ

Six ancient copper coins were found in the wreck of Huaguang Jiao "Ⅰ". The corrosion products on the surface of the six ancient copper coins were analyzed by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope and energy dispersive spectrometer (SEM-EDS), and X-ray flaw detector. The results showed that the main constituent elements of the corrosion products were Cu, Sn, Pb and Fe; the Chinese characters "Kaiyuan Tongbao (开元通宝)" on the surface of the copper coins were clearly visible, and there was a crack inside the No. 6 copper coin. Most of the copper coins were partially thinned due to corrosion, and the thickness was different, which should be the result of the corrosion and loss of the copper coin matrix. The black corrosion products on the surface of copper coins were mainly composed of copper blue and chalcocite, and some of them contained galena, galena and leadite; the white corrosion products mainly contained aragonite, calcite, and a small amount of pyrite. The white rust layer was cassiterite; the yellow-brown rust layer should contain goethite, magnetite, hematite and siderite. The grey rust was chalcocite, cuprite, chalcocite, cassiterite and quartz. In the corrosion products, no harmful patacalite inducing "bronze disease" was not found.