Zinc-coated steel substrates often have an additional organic coating applied, protecting the steel surface or altering its appearance for decorative reasons. These organic coatings are expected to have long lifetimes and since they are often used outside, they must be durable and have good weathering properties. The characteristics which make a particular organic coating suitable for steel protection will depend on the elemental and chemical composition of the organic material.
X-ray Photoelectron Spectroscopy (XPS) is an analysis technique which provides chemical bonding information from the top few nanometres of a surface down to many microns in depth. It is the ideal technique, for example, for identifying the carbon functional groups in an organic coating. XPS cannot detect hydrogen, however, but the complementary technique of Reflection Electron Energy Loss Spectroscopy (REELS) is able to both detect and quantify hydrogen. REELS can also be used to discern between aliphatic and aromatic carbon.
The Thermo Scientific Theta Probe is a multi-technique surface analysis system which combines XPS and REELS and also provides the additional technique of Ion Scattering Spectroscopy (ISS) as standard.