Pinholes in Nylon

Q. We are evaluating the use of nylon 6 as a replacement for nylon 11 and 12 powder coatings. In the course of our work we are experiencing a great deal of pinholing on the test panels. Nylon 6 requires higher temperatures. Could this be the problem? The metal sheets were primed and heated. B.B.

 
A. There can be many causes of pin-holes, so I cannot be certain. It is related to the substrate, the primer and/or the nylon coating. If the substrate is just steel with no bends or welds, it is not likely the source of your problem.

Contamination on the substrate is a possibility. As I understand, you do not have this problem when you run the nylon 11or 12, just with the 6. That would rule out a number of external causes (airborne contamination like aerosol spray). If everything is the same except the coating and temperature, it is very possible that the temperature is a factor. You should try running a sample at a lower temperature and see if the problem occurs with the nylon 6. If it does, then the temperature is not the problem. The problem may be the primer or the coating thickness. The primer may not work well at the higher temperature, it may be too thick, or the nylon 6 may be too thick. Also, make sure that there is not contamination on the surface that is causing the pin-holes.