Preheating parts

[jbotti1]

After about 3 months of planning I'm finally ready to powder coat. I have my Caswell hobby gun, sandblast cabinet, powder coating booth, and oven all ready to go. My first parts will be several small cast iron parts (cast iron engine thermostat housings). I have prepared the part by degreasing, sand blasting with black beauty, and sprayed/wiped down with brake cleaner. Being cast iron I feel I should preheat the part as a precaution. I figure this will prevent outgassing and burn off any residual oils. After doing some reading I have some conflicting information. Do I heat the part to 350 for say 20 minutes, let it cool to about 180, and then shoot?
If I was shooting regular steel should I preheat to aid in the powder being attracted to the part? If so what temp? How long?
thanks
-Joe

[Bud]

Re: Preheating parts

In the PC Book listed in this forum it say "Preheating means bringing the part to a temperature in excess of the cure temperature prior to coating. For example, running the part through the dry-off oven at 450 ?F and curing at 350 ?F. The theory is that the trapped air will escape in the preheat and no more will come out in the cure oven. Actual field evidence is that this can be an effective way to reduce the damage of outgassing by a large margin." I would think it would be fine to just go on and spray the powder as soon as you pull it out of the oven since that is the way a lot of people are doing the clear coats. I've always run the part through the oven first before I spray just to make sure everything is hopefully burned off, do forgive me if any of this is wrong.

[mtnbiker]

Re: Preheating parts

I do the same... prebake at about 50 degrees more than what I bake at(depending on the powder).

I always shoot cold. I havent had luck shooting preheated parts.