Delamination of Metallic Coatings

Surface analytical methods are often used to shed light on delamination problems. In the following example, a two component metallic coating showed poor adhesion to the underlying substrate. The sample was embedded in epoxy and cross sectioned. This exposed the interface of the coating to the substrate. By meas of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) fatty acid residues could be identified as the cause of the adhesive failure. As a consequence of this knowledge the procedure of precleaning the substrate was tested and specifically improved.

Coating Component A
Fatty acid residue
Coating Component B

Instead of cross sectioning the sample, as shown here, less cost intensive preparation methods can be used in cases of pronounced delamination. Layers can be separated using adhesive tape and a cross cut or by simple mechanic lifting with a surgical blade. Subsequently the backside of the delaminated layer and the exposed substrate surface can be chemically characterised to detect the possible presence of adhesion reducing compounds (e.g. mineral oil, etc.).