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Is there something about the powder-coating process that makes it more susceptible to the outgassing issue than paint?
I had a cheap local guy powder coat my intake, since he has a lot of experience doing 944 parts, but I am willing to bet now that those parts are not made of the same alloy. I'm already seeing bits of it chipping off in places, mostly on those plenums (S3). I got them done in black, so I think I can use paint and touch up the spots pretty transparently, as long as it stops the flaking off at some point. I guess we'll find out...
Not sure that powder is inherently more susceptible to outgassing than paint, either coating will suffer if the part's not prepped right. I'm eight years in on my powdercoated intake, the shop that did it had it for nearly a month, as Donald alludes to it's all in the prep. Post-strip they kept it outgassing in the oven for multiple days before they felt it was ready for color. The powder they used is from Rohm and Haas, which is intended to have a gloss clear put over it but I didn't want the clear because I was looking for the satin finish of the NOS intake pieces I've seen. So it looks like it has lost its gloss but it never really had (much of) it, on purpose. Has held up well:
Love the stock appearance of Rob's PCd intake. I didn't really like the high gloss and the deep appearance of the clear coat (even before it failed). Hindsight is 20/20...I'd have preferred a satin finish. Are there big differences in the quality/performance of different brands of powder? Or, is the final result really 99% determined by the prep and skill/experience of the person doing it? I'm seeing new tiny bubbles forming under the color layer after the 17 hour drive to Camp928 and back. So I see a rushed job on all levels at this point. 1. Insufficient time in the oven for outgassing. 2. Insufficient curing time. This one is more complex. The cam covers are looking pretty good, with only a few areas with the slight shattered look. As of this morning I can't find these areas anymore. I suspect due to being attached to the heads and bathed with hot oil from beneath the powder coat may have reflowed slightly and healed itself. I'll pull the intake tubes to inspect thoroughly. The intake being more massive (thick metal in many areas) needs to cure longer because it takes longer for the thick metal areas to reach cure temp. The shop relied entirely on the surface temperature - shot with an IR gun thermometer. Laying the powder on too thick can also contribute to the shattering of the clear after days or several weeks. In short - I went to the wrong shop.
After reading all the horror stories of PC I just opted to strip my S4 intake and cam covers and paint them with primer and four coats of high temp engine paint. That was about four years ago and 30k miles. They still look amazing and not a single problem. Mind you I spent probably 30 hours stripping them and I was very diligent about prepping. I never worried about off gassing the substrate just followed the instructions to the letter.
Jon asked me to provide pictures of my painted hardware, so here are some shots I took today. They look great- no peeling, cracking whatsover. I do have had to touch-up the letters with a paint pen a few times since but it takes a few seconds.
Chaukboss - Great result, especially considering this is 4 years after painting. I'll paint next time. Here's my failing PC job...our engine compartments look almost identical. Since this photo was taken the drive to Camp928 "cooked" it a bit more and caused small outgassing bubbles to form under the color coat...a new problem. Even if the job had been a success, the cost would not be worth it to me if one can achieve rattle can results and durability like yours.
Here's my second 928S4 Intake refresh in the all-done state; sent back to Joe in Las Vegas yesterday. Media blasted with Plastic, ran a scope down each intake runner and all around each side tank looking for what you all herein have said has been the death of many engines (but I have hypothesized the reasons for such disasters - and the DIY is at fault due to inadequate technique, tactics and equipment). Epoxy primed, painted in Dull Aluminum silver, and a clear coat matte finish to avoid the high gloss appearance.
06-28-2018, 12:14 AM
