Discoloration of Powder

n order to powder coat a grey nylon furniture part, I preheat the part, powder coat it with a white coating, cure the white coating, and then apply a powder clear coat over the white and cure that. What could be causing the part to come out of the oven with a pink appearance?

Ask an Expert From: 11/2/2012 Products Finishing, , from Products Finishing magazine

Q. In order to powder coat a grey nylon furniture part, I preheat the part, powder coat it with a white coating, cure the white coating, and then apply a powder clear coat over the white and cure that. The issue I have is that when the part comes out of the oven it appears pink. I have applied the white and the clear coatings on other nylon parts from another company, but they don’t come out pink. What could be the cause of pinking in this scenario? J.S.

A. Nylon is a thermoplastic material that can be affected by heat. I suspect the heat of the oven is causing some breakdown of the nylon during cure and that is creating the discoloration. There is a difference between the composition of the nylon that is showing the pink color and the other parts you have sampled. See if you can find out something about the nylon composition and how the two different products compare. Also, check film thickness and make sure you are getting enough to hide the substrate. 

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