Gold Leaf Corrosion in Moisture Acid Atmosphere at Ambient Temperature

Many cultural relics adhered with gold leaf (e.g. gold foil) are found damaged seriously in recent years. In this paper, gold leaf was exposed in the imitating atmosphere of moisture SO2, NO2 and their mixture to investigate its corrosion possibility in environment atmosphere at ambient temperature. Following phenomena were observed. The gold leaf was corroded in all these three atmospheres, which is contrary to the common sense that gold can only be corroded in aqua regia at ambient temperature. In SO2 atmosphere, the main reason of the corrosion is the preferential oxidation of the impurity of Cu. In the atmospheres of NO2 and the mixture of SO2 and NO2, the main reason of the corrosion is the combination of the preferential oxidation of the impurity and the oxidation of gold itself caused by the high defect density stemmed from the severe cold deformation during its processing. The discovery that gold can be corroded in moisture acid atmosphere at ambient temperature expands the understanding of the character of gold, and provides beneficial guidance to the protection of culture relics and modern artworks decorated with gold foil.