Photoacoustic FT-IR spectroscopy of natural copper patina

摘要

Fourier transform infrared photoacoustic spectroscopy (FT-IR PAS) has proved to be a useful tool for nondestructive testing of copper corrosion layer (patina) formed in the atmosphere. The samples cut from a piece of the roof of the Stockholm City Hall were examined without any additional pre-treatment. The components of the patina - brochantite Cu_4(OH)_6SO_4 antlerite Cu_3(OH)_4SO_4, basic cupric carbonate Cu_2CO_3(OH)_6H_2O as well as some other minerals were identified. The depth profiling capability of FT-IR PAS was used to determine the degree of photoacoustic saturation of the spectral bands.