By means of infrared spectroscopy vibrational and rotational states of molecules are excited. One can determine the chemistry of the functional groups like hydroxides, carbonates, sulfates, esters and so on. The IRRAS technique is used for surfaces, whereby the IR beam measures in grazing incidence to the surface. In addition polarization modulated light can be used to get a very high sensitivity for thin films or organic monolayers on metal surfaces. Another advantage of PM-IRRAS (Polarisation modulated infrared reflection absorption spectroscopy) is that bands of atmospheric water and carbon dioxide can be eliminated.
Development of sulftic- and sulfatic corrosion products on a zinc surface. Weathering at 80% RH and room temperature. Measurements every 15 min. One recognizes a steady band growth.