Powder Clinic: Fillers for Powder Coating

Q. Do you know of any type of filler (putty, fiberglass or bondo) that powder will stick to, can be sanded and will take the high temperature of powder cure (350° to 400°F)? I run a powder coating line and apply powder manually. It is cured using conventional gas flame convection oven. We have small holes and rough areas on the part surface that we need to fill and smooth out. Hopefully you can help me out with a suggested product to do this.

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A. This question pops up every few months and I am sure it has been answered before by me and others. There are a few products that can be used for this task. The trick is to find one that is cost effective, easy to apply and works reliably well. I have used a few products successfully but there are two that seem to be the most successful among knowledgeable coaters. Spectrum Powder Manufacturing in Calgary offers a higher temperature vinyl caulk that can work. It can be applied from the tube over a clean and dry surface and smoothed with an air-driven tool. Spectrum was sold to Cloverdale Paint and I have not tried to buy this product for some time now, so not sure if they still offer it. Another product that has worked well for powder coaters is Thermobond-3. It is a good filler that is simple to apply and easy to sand. Lab Metal Epoxy Putty by Alvin Products has also been used by some coaters. It is always recommended to test some parts before committing to a full scale production batch of filled parts, however.  

Originally published in the October 2016 issue.