Clear coat not sticking to valve cover

[dwb]

I'm attempting to clear coat a bare aluminum valve cover, but having a hard time getting it to stick. I used "Rust-Oleum Gloss Clear 600 Degrees Engine Enamel Spray Paint." It looks good when cured but it will peel/flake up with just my fingernail. Seems like it isn't sticking well enough.
The surface is completely clean, I used both a heavy duty degreaser and just before I blasted it with brake cleaner wiped and let dry. Some surfaces were sanded like the raised letters and other surfaces were wire wheeled. Others were just stripped of original paint.

Not even the raised letters will stick, and those were sanded really good.

Before I strip it and try again, what can I do to make this work? Maybe a different clear will stick better? I'm kind of concerned about heat, but is that even something to worry about? How about prep, what can I do? I'm really aiming for a raw aluminum look in some areas.

 

[92AWDHX40]

I use 2k clear coat works great, i dont really worry about heat, im going to redo mine soon powder coat it and forget it have it cleared once its coated.

 

[dwb]

Just a few pics for funzies. The peeling clear was my fingernail.

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[92AWDHX40]

Again the 2k has a hardener grab some off Amazon or napa.

 

[Jk's97DSM]

Did you run a torch across it before coating to get rid of the moisture?

 

[92AWDHX40]

I use a da sander myself

 

[dwb]

Did you run a torch across it before coating to get rid of the moisture?

I did not. I never knew it was a thing until now.

 

[jdxnc]

These valve covers are saturated with oils from years of use, the only way to get something to properly stick is to bake the oil out.

 

[South Dakota]

Aluminum does not play well with paint. As 92AWDHX40 said, you need an epoxy type paint to get it to stick without flaking. Alternatively you can clear anodize it. The rest of the spray primers that you can get for aluminum are going to change the base color. Make sure that you brake clean the surface, then use the residue free cleaners for electrical contacts before you try this again.

 

[EC17PSE]

Painting aluminum normally requires an etch primer to bite into so it holds. But to preserve your finish you cannot do that nor scuff up the surface. So you may want to look into a solvent type based paint or a 2k but have to be safe with 2k and fully protect yourself! Its very horrible and needs proper mask and / or fresh air device! You will get ill from it if breathed in

 

[Jk's97DSM]

I did not. I never knew it was a thing until now.

I learned about it a while ago from a video. Surprised the hell out of me on what came to surface and the moisture in general. I hope it helps. I’ll be spraying this one but stopped because I watched that video.

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[dwb]

I learned about it a while ago from a video. Surprised the hell out of me on what came to surface and the moisture in general. I hope it helps. I’ll be spraying this one but stopped because I watched that video.

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So like a small propane torch or do you need more heat like an oxy-acetylene? Can you link the video?

 

[Jk's97DSM]

Propane works.
I looked but I think it was a short on YouTube.

 

[jed344]

2k products work much better. I have never tried to clear raw aluminum though. I would assume already baking it is needed to draw the oils out. Then any kind of 2k clear likes 800-1,000 grit scratch. 2 coats and wait for clear to tack up before second coat. I will say again never have tried this exactly and also have doubts it would handle the heat.

 

[dwb]

No wonder why so many people powder coat them.
I thought clear on aluminum would be like painting steel. I'll be the first to admit I should have done more research before I blasted clear engine enamel on it. Live and learn.
I'll re-strip it and then rethink my approach. Etch primer seems to be a logical next step if I'm willing to take away the raw aluminum look. 2k clear, as suggested, has piqued my interest too. I've never used it so thank you for the suggestion and health warnings. I need to do some more research on that product and the prep work to make it work. Worth a look before the etch primer option.
Working for an aircraft manufacture, with an in-house paint shop, I should just go pick the painters' brains. After all, their canvas is all aluminum and work highly critiqued. Surely they have some good pointers (and maybe some leftover supplies).

 

[dwb]

I had a quick chat with one of our aircraft painters today. When I said aluminum, he immediately said etch primer first, then a regular primer coat with light sanding, then whatever top coat I wanted. That's the only way to make anything stick. Etch primer or nothing.

I asked about 2k clear directly on aluminum and he said that wouldn't stick either. Then I mentioned the torch idea and he just shook his head and laughed.

Back to square one. Stripped and ready for another go. Not the best specimen but at least not cracked.

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[Drewpy Dawg]

Baking it to remove oils would still be a good idea before spraying primer. Put it in the oven at a couple hundred degrees for a while then clean it really well with a degreaser. You don't want any of that stuff bubbling up out of the aluminum when it gets hot on a running engine after you've painted it. It's an important step even when powdercoating aluminum.

 

[CrackedDSM]

I had a quick chat with one of our aircraft painters today. When I said aluminum, he immediately said etch primer first, then a regular primer coat with light sanding, then whatever top coat I wanted. That's the only way to make anything stick. Etch primer or nothing.

I asked about 2k clear directly on aluminum and he said that wouldn't stick either. Then I mentioned the torch idea and he just shook his head and laughed.

Back to square one. Stripped and ready for another go. Not the best specimen but at least not cracked.

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I know you want that raw finish, but honestly duplicolor and the other brands all make a pretty damn decent flat aluminum spray that I use to mimic a "new" look. My fuel rail in my build thread was painted with that same flat aluminum paint and it turned out awesome. Not chromey or gaudy, just looks like clean new metal. It's not gonna look like this picture(unless you went with a metallic gray!) but it'll look like new metal.

Just an idea.

 

[dwb]

Baking it to remove oils would still be a good idea before spraying primer. Put it in the oven at a couple hundred degrees for a while then clean it really well with a degreaser. You don't want any of that stuff bubbling up out of the aluminum when it gets hot on a running engine after you've painted it. It's an important step even when powdercoating aluminum.

I better keep my garage stuff out of the wife's oven. Maybe I'll toss it on the grill
I already soaked it for a week+ in heavy-duty degreaser trying to get the baffles cleaned out. Kind of why I have to paint it now

I know you want that raw finish, but honestly duplicolor and the other brands all make a pretty damn decent flat aluminum spray that I use to mimic a "new" look. My fuel rail in my build thread was painted with that same flat aluminum paint and it turned out awesome. Not chromey or gaudy, just looks like clean new metal. It's not gonna look like this picture(unless you went with a metallic gray!) but it'll look like new metal.

Just an idea.

I briefly thought about this idea too but I really wanted the swirly brushed aluminum look, which I had going in the well area before the last strip oxidized it. Plus I wanted the machined look of the raised lettering that I achieved with sand paper. Maybe the lettering is still a possibility if I sand it down afterwards and leave it raw. The rest would be a colored or black topcoat.
TBH, I've always loathed it when people paint DSM transmissions to make them look "new." They never came like that from the factory. Even the big shops do it, but it just doesn't do anything for me. I'd rather see aluminum, even if it's oxidized.

 

[CrackedDSM]

I better keep my garage stuff out of the wife's oven. Maybe I'll toss it on the grill
I already soaked it for a week+ in heavy-duty degreaser trying to get the baffles cleaned out. Kind of why I have to paint it now


I briefly thought about this idea too but I really wanted the swirly brushed aluminum look, which I had going in the well area before the last strip oxidized it. Plus I wanted the machined look of the raised lettering that I achieved with sand paper. Maybe the lettering is still a possibility if I sand it down afterwards and leave it raw. The rest would be a colored or black topcoat.
TBH, I've always loathed it when people paint DSM transmissions to make them look "new." They never came like that from the factory. Even the big shops do it, but it just doesn't do anything for me. I'd rather see aluminum, even if it's oxidized.

Fair point. There's gotta be a way to mimic it though. Guys can recreate a "patina" effect on older vehicles by layering paint and sanding it...what if you did that with some metallic gray and flat aluminum layered? You could sand it in swirls. Might end up looking cool.

 

[dwb]

Fair point. There's gotta be a way to mimic it though. Guys can recreate a "patina" effect on older vehicles by layering paint and sanding it...what if you did that with some metallic gray and flat aluminum layered? You could sand it in swirls. Might end up looking cool.

Possible...but I'm not that skilled
I punch a keyboard for a living...on or off. No in-between.

 

[CrackedDSM]

Possible...but I'm not that skilled
I punch a keyboard for a living...on or off. No in-between.

I dunno if I'd say skilled, but I enjoy painting. Send it to me and I'll see what I can make happen. Or I'll do it on my spare VC. I'm curious now.

 

[Drewpy Dawg]

I wanted the machined look of the raised lettering that I achieved with sand paper. Maybe the lettering is still a possibility if I sand it down afterwards and leave it raw. The rest would be a colored or black topcoat.

That's pretty much what I'm planning to do with mine. Paint it with red enamel and then sand the red off the top of the letters with a sanding block and polish them. It will require some maintenance to keep them looking polished but I'd much rather do that then try to carefully mask them.

 

[CrackedDSM]

That's pretty much what I'm planning to do with mine. Paint it with red enamel and then sand the red off the top of the letters with a sanding block and polish them. It will require some maintenance to keep them looking polished but I'd much rather do that then try to carefully mask them.

Old picture but that’s what I did with mine. I used caliper paint too so it’s tough AF and heat/fluid resistant.

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[dwb]

@CrackedDSM that looks good. How did you do the lettering? Did it oxidize quick/easy and did you have to polish them? Did you use etch primer?

If my clear coat idea worked, I was just going to topcoat the letters in color with the rest then wipe clean before it dried.