| Search our quarter-million Q&As |
Home of the finishing HOTLINE since 1989
-----Small spots and craters on powdercoated material
2005
Dear Technical Whiz
Some of our powdercoated material has come out of the oven with spots and small craters.
Please advise whether this might be a metal treatment problem or powder application issue.
Powdercoating - Cape Town, South Africa
2005
I'm not the whiz you're looking for, Bob, just the first to see your question.
Either could be the problem. A third cause is even possible (like bad powder), but we need more data (what is the substrate, what is the pretreatment, what is the powder). A picture of the problem would be great. Meanwhile, please start with these similar questions already posted--letters 834, 8523, 31579--and see if they help at all. Good luck, and hope to hear more info from you.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
Hi Ted
We are coating aluminium, using a chromate pre-treatment.
The surface blemishes are either small craters or round blemishes.
We have eliminated the water or oil in the air line factors and have reset spray guns' voltage. The whole pre-treatment system has also been checked thoroughly. Still a number of blemishes and craters visible.
Regards,
- Cape Town, South Africa
2005
2005
Hi,
TGIC free powder can create blisters if heavily applied - this is due to water vapor that is evolved and trapped in the film during the cure. Another reason worth investigating is air entrapment - preheat the aluminium 80 °C (removes the air)and whilst still warm apply powder.
Let me know if there is any improvement.
Terry
Birmingham, United Kingdom
Thanks for the pickup, Terry -- Ted.
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.