MONITORING OF MODIFIED AL SURFACES WITH OPTICAL REFLECTION TECHNIQUES: APPLICATION OF VISIBLE AND INFRARED SPECTROSCOPIC ELLIPSOMETRY TO VARIOUS CONVERSION COATINGS

摘要

Optical reflection techniques have been used as versatile tools for the characterization of thin films on metal substrates. Three case studies which are particularly complex from optical point of view are presented. First, the optical behaviour of porous anodic films formed in phosphoric acid is studied with spectroscopic ellipsometry (SE). This porous film is significantly more difficult to investigate than more finely featured sulfuric acid films which were studied previously. An optical model which reveals the integral morphological characteristics of the phosphoric acid film is developed. The second case deals with morphologically relatively featureless chemical conversion coatings formed in chromate-phosphate solution. The complex composition of these films imposes the use of complementary optical techniques, i.e. IR and Raman spectroscopy, to identify the various constituents. Finally, the third case introduces IR-SE for extremely thin film characterization, e.g. monomolecular polymeric dip coatings on AL