Coatings

More than esthetics

Coatings and paints are not merely aesthetic. They also have extensive protective functions. These paint properties are strongly affected by possible inclusions of particles, the formation of gas bubbles or process issues. It is, therefore, not surprising that coating defects that occur in practice are examined as quickly and comprehensively as possibleto be able to identify and eliminate their causes. The following example shows the results that can be obtained by means of a Time-of-Flight Secondary ion Mass Spectrometry (ToF-SIMS) analysis:

Lacke

Paint craters

Investigating coating issues

Modern automotive coatings have a variety of tasks. The multi-layered structure of cathodic electro-deposition, filler, basecoat and clear coat protects the body from corrosion and can withstand weather, stone chipping, winter road salt and car washes for years. Paint craters or process issues endanger this protection, impair the optical quality of the surface, thereby causing enormous business damage.

Coating flaws can be caused by inclusions of particles and fibers, by surface contamination of the surface to be painted but also by blistering. Depending on the respective fault pattern, the causes can be clarified by suitable analytical methods such as light microscopy, infrared spectroscopy, SEM-EDX or ToF-SIMS.

Cleanliness and dust prevention are observed meticulously in the application of high quality coatings to avoid the formation of paint craters as much as possible. However, if paint craters or flow problems occur, it is necessary to investigate as quickly as possible. ToF-SIMS is an established method for such investigations. The method can identify the lowest levels of inorganic and organic matter on surfaces less than 100 μm in diameter. In the example shown, the coating layer shows many distinct craters of different sizes close together. In the craters, fluorine-containing hydrocarbons are detected with high intensity (see figure). By comparative investigations, these could be assigned to a high performance lubricant based on a perfluorated polyether (PFPE). This was used in the production plant to lubricate the conveyor systems and was dripped onto the surface. By attaching suitable shields, this source of error could be eliminated. This analysis provided valuable information for the identification and elimination of the source of the problem.

Coating Defect

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