Swall, When I was in the powder coat industry, the typical aluminum cleaning process was as follows: remove any grease with solvent based cleaner (MEK), remove any coatings with media blasting (thin components may recieve alternative method), outgas cast aluminum at 225°F for 45min, degrease with solvent or vapor degrease, then coat.
NickE, our oven control used a single thermostat, the oven was a convection type with furnace box on top and a large blower. heat surveys typically showed a maximum deviation of 10°F from nominal. As far as hot spotting the metal, we'd let heavier materials soak longer (up to an hour as stated in my first post) as the cure time is typically only 15 minutes once material has reached cure temp.
I guess I phrased my question wrong before, if an A356 casting is already at the T6 condition would an hour at 400°F age it even partially to another more brittle condition? which condition would this be? My ASM spec only shows it going to the T6 aging.
Also, how would 400°F for 1 hour affect forged 6061-T6? Would it cause any grain restructuring? My understanding is that strain relieving occurs pretty close to the anneal temperatures, but then again, I'm not exactly a materials wiz.
On a semi side note: I found that BBS uses both a powder coat primer and clear coat for their cast wheels.
