Analysis of Multi-layer Coating Systems
A correctly applied paint system, e.g. a primer-undercoat-gloss, will have the correct components applied in the right order at the appropriate film thicknesses. We can check all of the above provided we are supplied with one or more thumbnail-sized intact flakes that include all the layers present from the topcoat down to the substrate. In some cases all that is required is to section the flake and examine it using optical microscopy. This method will enable us to determine the overall film thickness of the flake. The thickness of the individual layers can also be measured providing there are sufficient differences in colour between them.
The techniques used for the analysis of fully formulated coatings can, in principal, be applied to the identification of the individual layers of a paint flake. In practice the only limitations are the size of the flake and the ease with which it can be dissected to reveal the layer of interest. In situations where an elemental analysis is sufficient, Scanning Electron Microscopy-Energy Dispersive Spectrometry (SEM-EDS) is particularly useful since it enables the elemental composition of the individual paint layers to be determined without the need to dissect out each one.