Got to do a couple test pieces, an aluminum Ford thermostat housing and small steel bracket I made for the intake/carb project. I took the advice form here and chormed them both at the same time, then let one cool before clear while the other I cleared right away. In the end both pieces turned out great, and I learned some on the way.
I tried to follow the Eastwood instructions as close as possible. For chrome and clears, they say to bake at 375 for 20 min after flow out, and NOT preheat above 375 as it could cause yellowing or other bad affects. Their other powders say to preheat at 450 and then bake at 400, so I thought it may be a key piece of information as they are very clear about staying at 375.
I sprayed both at the same time. Hard to tell when you have the "right amount" of powder, I can tell when I have full coverage but don't know if I should keep adding or leave it as-is. The thermostat housing was very bumpy, maybe it would have benefitted from a little thicker coat as it didn't really smooth out the bumps much if any. In any case, coated both on the oven rack with the ground clip attached to the rack, preheated the oven to 375, put the pieces in, went and started a load of laundry, when I was back it had already flowed out so I set the timer for 25 minutes. I did 25 instead of 20 because some of the info I'd read online said the undesireable "greying" could come from the chrome not being completely cured, and they recommended a longer cure time, as much as 40 minutes, so I thought an extra 5 minutes couldn't hurt.
Took the oven rack with the pieces out, removed the thermostat housing to cool, and coated the bracket with clear. My IR thermometer was showing about 150 surface temp when I did the coat, may have left it a little longer than I should have, but the powder still seemed to stick and melt slightly on initial application. Cooked it for 20 min at 375, pulled it out, and it still looked chrome! But there was major orange peel in the clear on a couple surfaces, which reading the Eastwood instructions I concluded that I didn't get a heavy enough coat. Oh well, didn't care how well that piece came out anyways.
Put the thermostat housing on the oven rack, started spraying clear, it was only sticking in some places, REFUSED to stick on some of the surfaces. I tried both the high and low voltage setting, no luck. Ok, back to the troubleshooting guide. It recommended preheating, so dusted all the clear powder off, stuck it in the oven five minutes, then pulled it back out, attached the electrode, and immediately shot the clear. WOW the clear powder melted/flowed out as soon as it touched the surface, was able to get a nice even coat very easily, GREAT! It looked grey, but I didn't panic yet, figured I'd wait to see how it looked after curing. In the oven it went.
While I was waiting for the thermostat housing clear to cure, I figured the preheating worked so well, maybe I'd try another coat of clear on the small bracket, to try to cure the orange peel. So I hung the bracket in the oven for a few minutes, then pulled it out and shot it with clear. Instant melt, nice even full coverage, just like the thermostat housing. Hung it back in the oven for another 20 minute gure.
Five minutes later the thermostat housing was ready to come out. It looked great, no noticeable loss in chrome-ness, and on top of that it felt so smooth and glossy.
Fifteen minutes later I pulled the bracket out. Wow, it worked, the orange peel was gone, now I had a very thick gel-coat looking finish, must have gotten a little too much clear on! You can actually see in the pictures what I'm talking about.
In both cases, I'd say the chrome finish turned out as good as expected, neither greyed out. I'd say I sufficiently thrash-tested what you can get away with applying the clear, best I can conclude is either the Eastwood chrome is very tolerant of different clearcoating processes, OR, getting a perfect initial cure of the Chrome is the secret to having good chrome results. Given the difficulty I had coating the cold piece, and the fact that the peice that didn't get a chance to cool still turned out good, I think the best method is to cure the chrome as instructed, and clear it immediatedly after removing it from the oven (don't let it cool at all), and just be careful not to get too much clear as you can get runs doing the hot coats.
Here's some pics of my experiment, will post pics of the coated intake in my Makin Progress thread ("Motorcycle carbs on tunnel ram"). Oh, and given how rough the thermostat housing turned out, I decided to smooth the tunnel ram out a little with the die grinder and some sanding cartridge rolls. I'm not going to be too picky on the end result, not planning on it looking professionally done, but I think an hour with the grinder will make the end result look quite a bit smoother.
The "Paint Booth"
The Bracket after second coat of clear:
The Thermostat Housing after chrome, no clear:
The Thermostat Housing after clear, tried to get the angle identical but was a little off so the reflection isn't quite the same, but it still looks great:
The finish is definitely not chrome. It is very chrome-like, or like slightly dulled polished aluminum, but in any case I'm not looking to replicate real chrome I just want something that looks cool and holds up well, and I think I'm going to be very happy with this.