Multianalytical in situ investigation of the initial atmospheric corrosion of bronze

Atomic force microscopy (AFM) and infrared reflection absorption spectroscopy (IRAS) were used for in situ investigations of the initial atmospheric corrosion of bronze. In addition ex situ XPS investigations were carried out on the samples before and after the exposure, as well as on the sputtered bronze sample. Investigations were carried out in synthetic air with 80% relative humidity (RH) and synthetic air with 80% RH with 250 ppb SO₂. At 80% RH, small features covering the surface were observed with AFM, whereas IRAS detected that more water is adsorbed on the bronze sample surface compared to pure copper. Large features on top of smaller features were observed with AFM on the bronze surface exposed to SO₂-containing humidified air. These large features were identified as copper sulfite. Furthermore, cuprous oxide was detected approximately 500 min after the introduction of SO₂. This fact and the XPS results indicate the formation of a protective lead oxide layer already during the preparation of the sample, which is destroyed by the SO₂-containing environment and leads to the formation of cuprous oxide and copper sulfite.