Different Appearance

[Julio82]

Hi everyone

we are having trouble repainting parts using a bright white TGIC (see testpanel.JPG). When we rework the parts we obtain a textured appearance (see badtestpanel.JPG).

In the past we had some issues dealing with outgassing, so our supplier gave us a different powder and since we start using the new powder the outgassing is gone but when we try to rework any part we are getting the appearance that you see in the pictures.

We have received different opinions, someone told us that this is back ionization, someone else told us that this is improper curing, someone else told us that it is a problem with the powder chemistry.

Does anyone have been dealing with a similar problem or Does anyone of you could give us some advice concerning this issue

Any input will be appreciatted.

[Popeye]

Re: Different Appearance

Best bet would be to talk to the powder supplier. To many variables to take a guess

[bzer1]

Re: Different Appearance

Julio, What is your rework process? I'm not so sure it looks like back ionization. It could be that the different formula your supplier gave you might be causing a cross contamiation problem. It has the appearance of beading on the surface. I will assume that your cure temp on the rejects is the same, and your intended film thickness is also the same. My suggestion is to try a test piece at a higher temp to see if it beads. Also try to lightly sand a test piece, shoot it, and recure. Let us know how you make out.

[Julio82]

Re: Different Appearance

For reworking parts we always sand the parts, we were using a 390 F set point in the cure oven. We increased it to 400 but we still have the problem.
At this moment we are talking with our powder supplier to see if there's something different with the formulation

[PowderVisions]

Re: Different Appearance

I believe that the problem is because during the cure cycle, there is offrgassing of different gasses. Some remain upon the surface after the cure is complete. We see this sometimes when we go to apply silkscreen over a topcoat. Usually, it will happen more and more as you attempt to recoat and recoat. This is why it is important to sand the surface with clean sandpaper and make sure you wipe each piece with pure water or isopropyl. Water that hardness to it will also leave reactions. Remember when you washed your car and left it to dry in the sun and saw those white spots. Well, even if you don't see the white, it's there.....