Vibrational Spectroscopy and XPS for Atmospheric Corrosion Studies on Copper

The possible use of Fourier transform infrared reflection‐absorption spectroscopy (FT‐IRAS) and Raman spectroscopy for surface studies of thin (<10 nm) corrosion products on Cu has been explored. Cu samples were exposed to 75% relative humidity and 25°C in flowing air, with additions of 0.25 ppm of SO 2 and NO 2 . X‐ray photoelectron spectroscoy (XPS) and cathodic reduction revealed that the corrosion products consisted mainly of an initially formed layer of Cu(I) oxide, a layer of Cu sulfite growing outside the oxide, and a layer of Cu(II) nitrate growing outside the sulfite. FT‐IRAS lines from approximately 1‐nm‐thick films of sulfite or nitrate can be detected and interpreted, in close agreement with the results obtained by XPS. The only phase to be detected by Raman spectroscopy was Cu 2 O , which most likely is due to a resonance Raman enhancement.