Painting Bare Aluminum?

[ManCave]

Hi guys,

I'm going to be painting a 4 x 6 foot aluminum sign that is brand new aluminum. Its going to be out in the sun for years and years and I don't want the paint to fail. There will be vinyl lettering and pin striping applied to the painted sign. A pro sign shop is doing that part. I have to get the sign painted first.

I've been doing a ton of reading. Sounds like I need to sand the aluminum with an 80 grit (but I see conflicting advice and some recommending a finer grit). Then it gets cleaned with white vinegar or acetone and then primed. For the primer, I see Zync Chromate recommended or a self-etching primer. However, apparently you can't paint the color coat over the self-etching primer you need to first paint over the self-etching primer with an epoxy primer?

I'm confused! Also, I don't want to spend $200 on materials. So I'm considering rustoleum instead of an automotive grade paint. I have to believe that if properly prepared, painted and then use a clear coat for UV protection I should be okay?

I could really use a detailed (as in step-by-step and with specific product/brand info) recommendation on how do paint this d*mn sign.

I would like to also hear if anyone has used rustoleum on aluminum and how it held up over time.

I know we have a lot of experts on here and I know you guys will clear things up for me!

Thank you!!!!

 

[dacuda]

ok ,i do this for a living.iv been in the sign industry for 25 yrs and most everything i build is aluminum and it always gets painted.you are correct in sanding it with 80 grit using a random orbital sander of some kind.you are also correct in using an etch primer but never put epoxy primer over etch primer.you can however use epoxy primer on aluminum.the product that i use is matthews which is big in the sign industry.they are now owned by ppg and their products are compatible.unfortunately for you material cost for this simple sign will cost you more than you want to spend.i would think the sign shop could paint it for you or bring it to a bodyshop but it will still cost you.can i ask why aluminum? do you already have it?there may be cheaper alternatives.what color are you wanting to paint it?

 

[ManCave]

Hi Dacuda,

I went with aluminum because it will never rust. Years down the road I could sand it, repaint and have new vinyl applied and it will be good for years again.

I already have the sign. Its been laser cut to the shape I wanted. I built the frame for the sign using rough sawed Cedar. The posts are 12 foot long 6x6's.

All that's left is to paint the aluminum, clear coat and then have the vinyl applied.

Does it pay to spray 1 coat of clear coat over the vinyl, to?

My son in-law built a spray booth in his shop and worked for years in a body shop. We're painting it at his place. I need to get the right materials lined up.

The color will be a dark green. PPG couldn't match the color I wanted. It's a pantone 560C.

 

[theoldwizard1]

ok ,i do this for a living.iv been in the sign industry for 25 yrs and most everything i build is aluminum and it always gets painted.you are correct in sanding it with 80 grit using a random orbital sander of some kind.you are also correct in using an etch primer but never put epoxy primer over etch primer.

I always like to pick the brains of a pro !

80 grit seems very aggressive. Any ideas why not a finer grit ?

I now a lot of folks swear by self etching primer and even recommend Rustoleum rattle can for small jobs. Why not zinc chromate ?

 

[Lelandwelds]

Have you considered finding a cooperative powder painter? ( It's a bit large for annodizing .) Maybe poor boy engine turning? #3 or #4 mill finish with an inflatable wheel? I use Molykote on my aluminum. How large an oven do you have access to? I think the experimental aircraft guys have a less expensive aluminum painting method. Next time use Alucobond panels? (IKEA sign letters are made from the stuff.) Fire truck rebuilders use a prepainted aluminum that has tough paint. How do you feel about red?

 

[astroracer]

Agree with old wizard.
Hit the aluminum with 600 grit on a D/A. Clean it with a good degreaser and shoot it with Zinc Chromate primer from Rustoleum. Use Rustoleum for your primary color as well. 30 or 40 bucks in paint. Done.
Do not clear over the vinyl. The paint and vinyl have very different expansion and contraction rates when they heat up in the sun. The clear will be peeling off the vinyl in a short time...
Mark

 

[Old Man Roger]

Why not just cover the whole thing in vinyl?

 

[astroracer]

Why not just cover the whole thing in vinyl?

That's an idea...

 

[ManCave]

Yes...that is an idea! I emailed the sign shop to see if that is a possibility.

That's an idea...

 

[ilovevocs]

Why not just cover the whole thing in vinyl?

This is what I would do if I didn’t have paint materials left over from another job.

 

[ManCave]

Ha! I just called a powder coating company and they want about $125 to do all 3 signs. I can't buy the paint, etching primer, primer and clear coat materials for that. I'm going to let the powder coaters do the work. Never dreamed I could have it done for less than what materials would cost me.

You guys got me thinking outside the box so thank you so much for the great suggestions! I knew I came to the right place.

 

[kazlx]

I was just going to suggest powder. Way better of an option unless you already have the materials. The correct powder will last a long, long time.

 

[dacuda]

Hi Dacuda,

I went with aluminum because it will never rust. Years down the road I could sand it, repaint and have new vinyl applied and it will be good for years again.

I already have the sign. Its been laser cut to the shape I wanted. I built the frame for the sign using rough sawed Cedar. The posts are 12 foot long 6x6's.

All that's left is to paint the aluminum, clear coat and then have the vinyl applied.

Does it pay to spray 1 coat of clear coat over the vinyl, to?

My son in-law built a spray booth in his shop and worked for years in a body shop. We're painting it at his place. I need to get the right materials lined up.

The color will be a dark green. PPG couldn't match the color I wanted. It's a pantone 560C.

if your son in law has a paint shop then your fine.you can get pantone 560c mixed in matthews if you have a distributor where you live.i personally don't like clear coating over vinyl for the fact that if the info changes(like a phone #) you will have to repaint sign instead of peeling just the vinyl.im surprised that ppg couldn't match it by using a color eye system to a paint chip.

 

[dacuda]

Agree with old wizard.
Hit the aluminum with 600 grit on a D/A. Clean it with a good degreaser and shoot it with Zinc Chromate primer from Rustoleum. Use Rustoleum for your primary color as well. 30 or 40 bucks in paint. Done.
Do not clear over the vinyl. The paint and vinyl have very different expansion and contraction rates when they heat up in the sun. The clear will be peeling off the vinyl in a short time...
Mark

600 git is way to fine for prepping aluminum for paint.80 grit is industry standard..i use 600 as a starting grit when i cut and buff cars or polishing aluminum.220 doesn't even offer the best adhesion for prime even with etch.but what do i know .i only do it for a living for a global 30 million dollar company.

 

[dacuda]

Have you considered finding a cooperative powder painter? ( It's a bit large for annodizing .) Maybe poor boy engine turning? #3 or #4 mill finish with an inflatable wheel? I use Molykote on my aluminum. How large an oven do you have access to? I think the experimental aircraft guys have a less expensive aluminum painting method. Next time use Alucobond panels? (IKEA sign letters are made from the stuff.) Fire truck rebuilders use a prepainted aluminum that has tough paint. How do you feel about red?

i was gonna suggest dibond(alucobond) also with a digi print or vinyl.

 

[Lelandwelds]

Chromate conversion from an annodizing shop is the way to go! Trivalent is more eco friendly. Huge tanks are the norm.

 

[ManCave]

The powder coating shop I was going to use wasn't going to sand the aluminum or acid etch it or anything. They were only going to degrease and paint. They had no idea how to paint aluminum, apparently.

I DA'd the aluminum with 80 grit. Found a new powder coating place that does know how to paint aluminum. Just waiting to hear back from them on a price quote. Even though I DA'd it they said they would hit it again right before painting. These guys apparently know about oxidation so I like these guys. The first shop was clueless.

 

[joeswamp]

I'm certainly no expert on this but I've heard it can be tricky to get paint to stick to aluminum. One technique I've heard about for car bodies: 1) Scuff with scotch-brite and 91% isopropyl alcohol, 2) Wipe with 25% phosphoric acid and dry it, 3) Apply PPG epoxy primer within 20 minutes.

You can then put sandable primer over the epoxy and use the epoxy as a sort of reverse guide coat.

Obviously you'd want to test this technique before you used it on anything valuable.

Anyway the point is you need some way of getting rid of the oxide layer if you want that paint to really stick. I've always wondered what techniques they used on the old high-end cars -- like what was the process on an aluminum bodied Rolls Royce or Aston Martin from the 1950s? How do they get paint to stick to aircraft?

 

[CudaChick1968]

The powder coating shop I was going to use wasn't going to sand the aluminum or acid etch it or anything. They were only going to degrease and paint. They had no idea how to paint aluminum, apparently.

I DA'd the aluminum with 80 grit. Found a new powder coating place that does know how to paint aluminum. Just waiting to hear back from them on a price quote. Even though I DA'd it they said they would hit it again right before painting. These guys apparently know about oxidation so I like these guys. The first shop was clueless.

Just a few things off the top of my head ...

If the shop has no experience with aluminum, you should run out the door rather than walk. It's one of the most common metals to powder coat and it turns out spectacular.

You should be able to get the "right" color from a powder supplier (my main one offers over 6,500 colors in stock and has the ability to custom-match your sample too if by some small chance they don't already manufacture it). Don't feel like you have to choose from an industrial coater's 6 or 7 "stock" colors because there is no limit ... powders can be mixed or layered to create any color you can dream up.

You can get high temp vinyl decals made per your specifications. They can either be permanently embedded between powder coats / colors, or used as a stencil to reveal a base coat color underneath. They will not discolor, shrink or lift if the job is done right and you start with proper high temp vinyl (your cutter will know what to use). This is a Harley gas tank decal my customer snagged on eBay which I applied over a base coat of light blue and top-coated with a candy blue on his control arms ...





A powder clear coat will provide extra shine, seal the colors and lettering, and provide the UV stability you need for the sign to last, not corrode or oxidize over time.

As long as you retain a qualified shop and are explicit with your instructions, you should get exactly what you had in mind. Keep shopping around until you find the right place who can turn your vision into reality. It may cost a bit more than you want to spend right now, but doing it right the first time will provide many, many years of beautiful, maintenance-free service and be the perfect representation of your business.

 

[ManCave]

Thanks CudaChick. I didn't know that hi temp vinyl existed or that you could do that sort of thing with it. Pretty cool! It wouldn't really work out for me because the paint shop would have to powder coat, then the sign shop apply the vinyl and then back to the paint shop. Not many paint shops would know how to apply that much vinyl.

I ended up finding a really good powder coating shop. They will sand with 150, acid etch and wash (triple wash) and then powder coat with an architectural powder that has good UV resistance.

Should be done in about 7 days. Then it will go to the sign shop for vinyl. Down the road, I suspect the vinyl could be removed and replaced and the sign would be good for another 10 years.

 

[CudaChick1968]

You're very welcome! It sounds like you're in good hands now. Post up some pics when you get it back.