powder coating oven tougher finish required

[d608454]

at the moment we are using a 8 metre oven ( made by maywick)
fired by 48 gas ceramic burners with a conveyer running though the oven
oven temp is 380c this is a lot higher than the powder coating temp of 180c ,we bake the powder coated parts for 4 mins any longer and we find that the parts burn or discolor,the finish we get is ok but we find that the power is not very tough (marks easily) we use polyester powder from du pont
The oven temp is very uneven starts at 30c one end increases to 380c other end
any suggestions to get tougher paint finish
thank you

[Hemi-T]

Lower your temperature and cure for a longer time. This allows the powder to flow out and adhere to the base better. How is your metal prepped? A slightly rougher finish (sandblasted or glass beaded) gives the powder something to adhere to. If the metal is polished to begin with, and cured too quickly, the "cured" powder can peel off. Consult your powder manufacturer for recommendations, but a general rule of thumb is 400F for 14 minutes. You can lower the temp to 375F and cure for 18-20 minutes. Consistent temperature also yields consistent results. If the temp fluctuates, the powder may not cure to it's best potential. I'm not a pro, but these are some of the basics I've learned here on the BBS, and by trial and error.

Hemi-T

[warchild]

My powder comes out nice and is very hard to remove from the part. but my powder marks easily too. i can't seem to get it as hard as a kitchin stove or washer there powder coated too but you can't mark them as easy as you can my powder. mine may get marked but it will not come off of the part. and i bake it like you said Hemi-T. But then again i have not tested all of the powder coating i did. i use a lot of diff powders everyday.

[Hemi-T]

Has the mark actually damaged the powder, or is it just residue from something that rubbed across the powder coated part? I powder coated some valve covers, and if I rub a rubber or plastic coated tool across them, it will leave a mark, but the mark comes right off. In other words, it doesn't damage the powder coated part. I haven't gotten really hostile with my powder coated items yet, so I don't know what the damage threshold is

Hemi-T

[warchild]

oh. yeah that is what it was..i just found out they bake Appliances in (25-60 seconds).

[DALE]

Appliances are almost always coated with straight epoxy powder, which is very tough. Most small powder suppliers sell polyester or hybrid powders which are much easier to mark or scratch.Some sell acrylic or urathane which aren't any better.Also appliances are coated when the metal is new and they have elaborite cleaning systems so you are at a bit of a disadvantage.