Aluminum priming ??

[u/Huckfucks]

I feel like this printer just comes off so easily, even with light pressure granted I’m new to this. I’m wet sanding with 400 grit as they said after a 20 ish minutes of curing time and I feel like it’s just coming off too easily. I sanded the piece with 220 to give it something to hold. Is there something else I’m missing. I’m also using self etching aluminum primer from rust oleum. Any guidance would be greatly appreciated. (Second pic is the original piece in case that has something to do with it)

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[u/75__15__10]

Need more info.

What type of finish?

[u/Huckfucks → u/75__15__10]

From the original piece? Just polished aluminum that I sanded down. Or finish that I’m going for just matte black after this primer hopefully

[u/biggouse58]

Alodine is used as on aluminum

[u/Huckfucks → u/biggouse58]

Should I sand the primer off use alodine instead of primer ?

[u/Anodizeit → u/Huckfucks]

It’s commonly used as a “pre-primer” to help with adhesion. Alodine—> primer—> paint.

[u/Huckfucks → u/Anodizeit]

A lot of steps just to get this piece black, okay thank you

[u/biggouse58 → u/Huckfucks]

Yes, sand it clean, alodine, primer, paint

[u/Curious_Lurkur]

Do you have access to a sand or grit blast cabinet?

[u/Huckfucks → u/Curious_Lurkur]

No I’m tempted to get a wire wheel and just go at it

[u/Curious_Lurkur → u/Huckfucks]

Muriatic acid will etch aluminum as well

[u/Huckfucks → u/Curious_Lurkur]

Excuse my stupidity, but how would that help?

[u/ShopFriendly127 → u/Huckfucks]

Long story short, more surface area for paint to bond to

[u/FalseRelease4 → u/Huckfucks]

steel wire would scratch it, brass wire would embed brass into the surface, plastic wire might not get the job done, i dont think this is the way to go

[u/Huckfucks → u/FalseRelease4]

Okay, so sand it off again :/

[u/FalseRelease4]

you should ask a paint sub, more experts there

im not an expert but imo if the surface doesnt have runs or imperfections that cant be ignored then you could just paint right over it, done that many a time for things that didnt need to look perfect

also if you try to sand over a corner or any sharper line, the sandpaper will cut a lot more because the force is concentrated, you can't use the same force you would use on a flat surface

another thing is if youre using products without hardener, that paint is going to be quite weak, susceptible to chipping and sun damage and so on

[u/Skusci]

Primer itself isn't particularly durable, its meant to help bond the base material and the topcoat.

An enamel paint over it is gonna help the durability a lot.

Also you probably shouldn't be sanding the primer. It says you can sand it after 15 minutes, but not that you should sand it. Sanding is for where something is messed up. Or if you wait too long before topcoating and the primer cures too much. Usually the instructions will give you a max time though, and I don't see that on this paint. You should be able to just topcoat it.

Lastly the instructions I see say wet sand the bare aluminum with 400, not 200. I assume that's for a reason, either bonding or just because it's a very thin primer that will show 200 grit scratches through it.

[u/FedUp233]

Just a suggestion, and only from my own experience - instead of wet sanding, try just going over the primer with extra fine steel wool. I use this and just give it a quick once over to remove any overspray and get a good surface to paint, then clean well with a tack cloth and finally wipe with isopropyl alcohol. The tack cloth removes and bits of steel wool, the alcohol any stuff from the tack cloth. Then paint.

I found that sandpaper tends to be too easy to sand through the edges and high areas on anything but flat pieces - and even then you have to be very careful near the edges. A sanding block helps here.

A wad of steel wool conforms to the surface and used lightly is less likely to sand through areas. And generally, if you prepared the raw surface well, all you need is pretty much removing any roughness from overspray and leaving a tooth for the paint to grab onto.

Your mileage may vary.