Painting aluminum

[CarlyBoy]

With a little research, looks like I can confidently paint aluminum sheet if it's properly prepared. Just one concern: the parts that are attached to the chassis. Specifically, when jacks, switches, and the like are tightened down, isn't there a chance the paint will chip under the pressure? Thanks for any help...

 

[EdT]

It depends on what kind of paint you are going to use, but most aerosol laquers and enamels will chip once dried or crinkle if turned with pressure against a lock washer, anyways you do need to have the jacks grounded to the enclosure anyways. I am thinking of using a lapping stick which consists of a wooden stick tipped with lapping compound on a drill press to clean up the area for a clean and professional result. around where the jacks will be inserted, but just small enough that the washer will cover it up.

 

[Cal Weldon]

Are you planning to etch before painting?

 

[CarlyBoy]

Yes, Cal, I was planning on etching the surface prior to painting. I pretty much assumed this was mandatory for good paint adhesion.

 

[Cal Weldon]

I find etching the most effective. The "other" ways of painting aluminum I haven't had much success with.

 

[CarlyBoy]

What kind of paint have you had the most success with, Cal? In my case it has got to stand up to the heat of tubes.

 

[Cal Weldon]

Barbecue paint maybe?

I don't know. My job was to load the extrusion into the acid and zinc tanks. I wasn't allowed near the spray booths. 😉 I just remember how important proper etching was to a good job.

EDIT: Most of the painting I have tried with aftermarket stuff was for touch up. All I know is that they don't work as well regardless of how well sanded or clean it was.

EDIT2: Is enamel a good paint for heat?

 

[grimberg]

I have had success painting aluminum using two different approaches, both of them with Rust-oleum products. The first method is to use Aluminum Primer and then any other paint spray over it.

http://doitbest.com/DoItBest/Main.aspx?PageID=64&SKU=782327

The second approach is to use Appliance Epoxy directly on the aluminum surface, with no primer. It is available at Home Depot.

http://www.rustoleum.com/product.asp?frm_product_id=33&SBL=1

It is more expensive and the color selection is limited, reason why I prefer using the Aluminum Primer.

 

[theAnonymous1]

I've used zinc phosphate based etch primer with good results. It was similar to this stuff.......

http://www.prestomart.com/cgi-bin/store/store_web_catalog.pl?ref=deerparkhotrods&pd=400135

I also suggest bead blasting the surface instead of sanding if possible.

 

[XEAGLEKEEPER]

When purchasing your primer get self-etching primer. I've had real good luck painting aluminum intake manifolds with this type of primer. Of course I had beadblasted the surface first.🙂

 

[flg]

After solvent cleaning, use a zinc chromite primer... It works! 😀

 

[Mark A. Gulbrandsen]

I've spent half my life either painting alumnium or having it done.... rebuilding cinema projectors.

Be sure to have any alumnium you're painting anodized first with just a plain anodize (no color). If you don't have it anodized the alumnium will continue to oxidize under your beautiful paint and your paint job will last but a few years. This can be very disheartning if you've spent alot of time/money on the chassis/front panel of your project. BTW: The same applies with items being powder coated.

Mark

 

[CarlyBoy]

I had done a little investigation of anodizing, but had hoped to avoid it - seems like less chance a novice like myself would get it right than with painting. Only one shop in my town will anodize and price is steep. Could do it myself with a kit, but not wild about the chemicals and the setup required. Guess I'll have to investigate this further. Thanks for all your help!

 

[EdT]

Beadblasted with clear chromate, beadblasted with nickel plate and flash chrome is awesome.

Hammer finish paint might also be nice.

 

[Mark A. Gulbrandsen]

If there is only one place to get anodizing done in your city try sending your parts out to a city that has a bunch of shops. This will get you a very competitive price.... say for 35.00 which isthe minimum at the shop I usePilkington Metal Finishing you should be able to get ALOT of anodizing done. I've yet to ever exceed the minimum amount. Bead blasting is fine but the alumnium starts to oxidize again in just seconds. Applying Zinc chromate... something I've done alot of... is a good idea too if you don't mind the resulting thickness of several layers of paint.

Plating is not something I've ever done with alumnium... takes at least a copper sub base first and probbably a secondary nickle layer before the chrome can be applied. That would be the equivelent of having three plating jobs done lots of $$$$ but it would look nice.

Mark

 

[EdT]

Yellow and clear chromate by itself is very inexpensive. I have beadblasted AL enclosures and clear chromate for RF amps and they seem to hold up quite well to exterior environments. Beadblasting makes the skin more dense and less prong to nicks and scratches and no finger smudging as on a polished finish. Anodizing could be a better option since it is more resilent and can be done with multiple colors. The problem with plating is that they usually require several pieces before they get it right and stripping a bad plate is very time consuming.

Also, another thing to consider is to simply sand and buff the casing, it doesnt seem to oxidize once it is highly polished and if it does, simply use some metal polish and everything is shiny again. It would be ideal if the casing was to be made out of pewter as pewter does not tarnish and is highly polishable.