painting raw aluminum- what to use

[Techman]

So, Zinc Chromate has been off the market for two years now I was told from a auto paint shop

bullcrap

Its all over the world.
It is the best product to use for raw aluminum. Bar none.
It matter not what others said to use,,, but aluminum will tarnish under the paint. Soon the paint will lift and flake off. You must use an etching primer made for it. The holy grail is to use the right stuff otherwise you will have junk.

Be sure to clean the metal until it shines. That will give you the best adhesion.

Just for an example.. Aircraft use this for primer and the paint jobs last for decades.

http://www.google.com/search?q=zinc...61,d.aWc&fp=825dfea8c40efe65&biw=1440&bih=708

 

[John Butto]

bullcrap

Its all over the world.
It is the best product to use for raw aluminum. Bar none.
It matter not what others said to use,,, but aluminum will tarnish under the paint. Soon the paint will lift and flake off. You must use an etching primer made for it. The holy grail is to use the right stuff otherwise you will have junk.

Be sure to clean the metal until it shines. That will give you the best adhesion.

Just for an example.. Aircraft use this for primer and the paint jobs last for decades.

http://www.google.com/search?q=zinc...61,d.aWc&fp=825dfea8c40efe65&biw=1440&bih=708

That google search you have for zinc chromate in the rattle cans is not the same that they use on aircraft, unless it is a backyard homemade one. The aircraft zinc chromate primers were two part mixtures. The paint manufactures are developing new two part wash primers without the chromate, as the one I showed in my previous post. As anyone who has painted large amounts of aluminum knows that two part Zinc Chromate wash primer is the best, and you can still buy it.

 

[Techman]

That link I posted was in response to a previous post saying it was "discontinued. My post was to show that someone was very misinformed. It is STILL available in every form,, spray on, brush on or two part..

Second. His sheet is only a few sq ft for a sign. It is not aircraft skin. He only needs a rattle can at best. It will work just fine. A brush on product would be fine as well. We used gallons of spray on or brush on zinc chromate on aircraft corrosion repairs and never had an inspection red tagged.

But in any case using anything but a etching primer on aluminum will cause a fail. Any body who has painted aluminum knows that.

 

[Todd Jelle]

Aluminum is hard to get paint to stick to. Ive used self etching primers alone with some success.

There is an automtotive product called twin etch designed for aluminum. You scuff wash the parts with this and flush/rinse it completely. I always follow this with an automotive self etching primer before painting. This provides the best bond i have found.
I'm sure zinc chromate is also just as good

Twin Etch Product date sheet
http://www.martinsenour-autopaint.com/media/pds/english/8103.pdf

 

[Techman]

I figured aluminum cause it will not rust and that is what the street signs are...

Forgot to mention.. Street signs are NOT made from standard aluminum..

Street signs are made from a very specific aluminum alloy. It is nearly impossible to bend making it vandal proof. It is corrosion proof as well. This alloy is used as an MDOT standard. Driving along A1A in Florida you can see this material in use. The signs never corrode and last for years. Any one living alongside the seashore will know how harsh salt air is on every thing.