Rust-Oleum Flat Black Primer bonds surprisingly well to aluminum.

[red4]

Rust-Oleum American Accents 2X Ultra Cover Flat Black Primer (327911 PRIMER BLACK)

Bought some K&S aluminum tubes. Sanded a piece with 400 grit sandpaper, cleaned it thoroughly with 91% isopropyl alcohol, sprayed Rust-Oleum primer, and let it cure for just over 24 hours. I did a fingernail scratch test, and it bonded surprisingly well. I've never had a consumer aerosol paint product bond so well to metal before. I have used brushed-on Model Master Acrylics before, which bonded extremely well to aluminum. Not even those "self-etching" spray cans worked this well.

 

[joberg]

^^
Thanks for the FYI red4. I'd painted my alu tubes to support my 2001 Space Station docking bay with the same brand I thought the paint covered the metal well and could sustain some normal handling (mounting it to the brackets). I didn't do the "Fingernail Test" though.

 

[kermet]

I as well have had same results, but just know for inside projects only it does not weather well. Found that out the hard way on a out side project for Halloween it all slowly pilled away the primer is the right trick I used a cheep primer. Thanks for sharing

 

[Millenniumf]

Rustoleum X2 Flat Black and Ultra Matte Black are my go-to spraybomb primers. They stick to just about anything, are very resistant to scratching, and don't obscure details.

 

[Sluis Van Shipyards]

I'll have to try it. When I painted my Endor rifle a couple years ago, I first used an acid etch primer on the aluminum tubing, then black. The primer didn't stick worth a crap and I still had to do touch ups.

 

[sbaxter]

I haven't tried it yet, but RustOleum also makes a spray-can primer specifically for aluminum; I've seen it at Home Depot.

SSB

 

[red4]

Addendum: I don't remember what I did with the sample I primered in March, but between September and October I finally decided to finish the project it was meant for, so I bought 2 cans of Rust-Oleum Black Primer, and neither one performed the way I needed them to.

While the Black Primer bonds quite well to aluminum, the surface of the primer doesn't seem to want to cure properly. The slightest touch with a fingernail burnishes the surface, making it glossy, and it leaves residue on my fingernail. But actually removing the primer with my fingernail to expose the aluminum takes a great deal of effort; so that means it bonds effectively. Also, I have yet to find a paint that bonds to the primer, even from the same brand. I'm heading out to buy a third can, hoping I just encountered 2 duds, and the 3rd will work.

6:50pm edit: I bought a can of Rust-Oleum High Performance Enamel Flat Black 7578838 instead, just to see if it works as a primer.

 

[joberg]

^^
The "glossy effect" on a mat black paint is simply the oil from your skin. That's why I tend to handle those type of paint with a pair of cotton gloves.

 

[red4]

^^
The "glossy effect" on a mat black paint is simply the oil from your skin. That's why I tend to handle those type of paint with a pair of cotton gloves.

It's not, because Rust-Oleum Camo Black doesn't get affected that way, and it has the same flat black texture after curing. And the glossy marks on the black primer can't be washed away with soap. They are burnish marks from being too soft.

 

[red4]

Final report:

I am at a loss. In the final test I applied the Black Primer to a clean piece of aluminum. Let that cure for 5 days, with roughly 10 hours under a hot light per day. The primer cured and bonded really well. But then I applied paint, of the same brand, over that. Now, this is a paint that has never had any trouble curing hard after 24 hours. But this time, after 48 hours, it hasn't bonded to the primer at all. I maintain that the primer doesn't do what it's supposed to, and is worthless, unless you're trying to achieve a flat black look, and nothing else. I have one last theory to test, but not enough patience to try it out - for now. Whenever I paint onto styrene or ABS, I use Rust-Oleum Camo Black as a primer. It works remarkably well. The theory is to apply Black Primer, then Camo Black, then the final paint over that. As you can see from how old this thread is, who knows if I'll ever actually get it done.

The really dumb thing is that I tested Model Master Acrylics on the same aluminum, and discovered it bonds really well without any primer. The only reason I haven't gone ahead with this paint from the start is because I want a smooth, uniform texture, which can only be achieved with an airbrush, which I don't have. I need to just buy one already.

 

[ZeroSum]

Perhaps try a self etching primer if you're game for more experimentation.

 

[red4]

Perhaps try a self etching primer if you're game for more experimentation.

Already tried one a few years ago. It was a joke.

 

[laellee]

Don't know if this is a help, but Rustoleum 2X was always very chemically hot for me. I went through hundreds of cans 'back in the day' finishing armors, and this was my takeaway:
2x will stick pretty well to most reasonably prepped surfaces, be it foam/plastic/metal/primed/plastidipped/etc, and will recoat well within about 45 minutes. After that, unless i gave a solid 2+ days of dry time to cure/degas, it was a crapshoot; It might lay down OK, it might get gummy, it might crackle out like dried mud in areas (the most common issue for us) and have to be sanded right back off. It didn't matter if it was the same color, or even same can for that matter, it didn't matter if it was humid or dry, or if the temp varied within reason. Our group of builders tried all kinds of stuff, tested with surface contamination, troubleshooted, but in the end it was easiest to let it dry wayyy longer than the can recommendation before spraying over it (and it sounds like even that wasn't helping for you), sometimes 3+ days.
If the colors hadn't been so good for matching particular pieces (and availability) at the time, I would have switched to Duplicolor and called it a day. It's too bad, because that stuff can finish really well; there are still at least a couple of full Iron Man suits out there that we shot 8+ years ago in Rustoleum 2x, and they look great. :/

 

[Sluis Van Shipyards]

Perhaps try a self etching primer if you're game for more experimentation.

Already tried one a few years ago. It was a joke.

I agree with that. I tried Dupli-Color automotive self etching primer when I built my Endor rifle. The stuff didn't work at all. I had to go back and touch up the black after I painted it because some spots were flaking off.

 

[mung]

I have found that here in Australia the Rust Guard and similar Epoxy enamel spray paint sticks very well to aluminium.
It takes at least 24 hours to dry properly and you need a couple of light coats applied a day apart.
The flat black drys to the touch quicker but still needs a full 24 hours to fully dry.
It sticks much better going on raw than using an etch primer first.

 

[red4]

I have found that here in Australia the Rust Guard and similar Epoxy enamel spray paint sticks very well to aluminium.
It takes at least 24 hours to dry properly and you need a couple of light coats applied a day apart.
The flat black drys to the touch quicker but still needs a full 24 hours to fully dry.
It sticks much better going on raw than using an etch primer first.

That may be the solution, but epoxy paints tend to be very expensive, and I'm not that desperate yet.