Painting Diamond Plate Aluminum

[Chief_919]

I have a combination auxilary tank and tool box that is going in my 1028, but of course I don't want shiny aluminum in the back.

What the best best way to prep and prime it to ensure the paint sticks?

 

[zout]

OK - I will jump in here
If is weathered use a product called alodine after thoroughly cleaning the surface and this creates a ceramic type barrier. Good 2 part epoxy primer and paint.

New alum - make sure surface is cleaned - then jump to stage #2 of the above.

 

[John S-B]

If you have sandblasting capability that may be a good option. Might give better adhesion with a slightly rough surface. Just enough to take away the shine. Norfolk Southern did that with some stainless steel cars that had to be painted to match their steam excursion train when it used to run.

 

[Nonotagain]

OK - I will jump in here
If is weathered use a product called alodine after thoroughly cleaning the surface and this creates a ceramic type barrier. Good 2 part epoxy primer and paint.

New alum - make sure surface is cleaned - then jump to stage #2 of the above.

No matter weathered or new, aluminum requires a surface that has the oxide layer removed prior to paint application.

The fastest method is sand blasting and then using Alodine.

The problem is that Alodine is a chromated product which has to be handled properly or you contaminate the ground or water. I have a bucket that I use for my spent material and allow it to evaporate then dispose of it via the hazardous materials waste days at the dump.

Henkel Loctite the manufacturer sells a large felt tipped pen that contains Alodine 1132. Clean the surface with soap and water using a Scotchbrite pad, rise with clear water, apply the Alodine and allow to air dry. The advantage is that Alodine 1132 doesn't require rinsing while other forms of Alodine do.

The next fastest method is using a acid activated primer called "Wash Primer" which etches the surface for increased paint adhesion.

Any good automotive paint supplier can sell you wash primer. Follow the directions on mixing and application, then once dried, prime with a good epoxy primer and topcoat.

 

[zout]

Chromate conversion coating - Wikipedia, the free encyclopedia
I'm not new to this rodeo

 

[hndrsonj]

Both the Navy and FAA (A&P License) train to use Alodine, or equivalent, on all bare aluminum before priming with no exceptions.

 

[chemicaljohn]

Alodine would be the best to use. Doing sheetmetal work on aircraft it's the only way to go, and is required on aluminum structures. Epoxy may/ may not stick depending on how well you prep. I've always used scotchbrite and wiped with isopropyl or acetone. Paint doesn't stick to bare aluminum very well at all.
The other and probably easier to find option is a self etch primer, on aircraft we call it zinc chromate. You can find self etch with body work supplies anywhere from wally world to an auto parts store. Years ago I used aluminum diamond plate for a deck on a small trailer. Got a spray can of zinc chromate and a couple spray cans of cheap bedliner. Never came off.
Alodine is meant to dip the part for about 30 sec and rinse water. You could get away with brushing it on a horizontal surface, let it sit a bit and rinse. You want it to change the metal to a light gold color. It's the consistency of water, so in brushing it, if it's not scuffed well it won't etch well. Stuff's done like that on touchups on an aircraft repair where you obviously can't take the plane apart to stick it in a tank for a 6" area. Wear gloves working with alodine, it's an acid.... and it stinks. Plus, don't dump it down the drain.

I would go with epoxy or zinc (self etch) primer. Alodine would be great, but I think the other options would be way easier. Just make sure you scuff the surface good and clean good.

 

[flyxpl]

I use the washprimer and have never had any adhesion problems . Last time I bought alodine I could only get it in 5 gal. buckets .

 

[Bill W]

If it were me
I would etch it first ( blasting or chemical ) any of the box stores carry "Prep and etch" ( usually over where they keep the paint thinners). then I'd use a zinc phosphate primer ( or chromate if you can find it ) which I was lucky to find at a local aircraft supply company ( any marine store will carry it also ). If i'm using a automotive paint then I'd prime over the zinc primer with automotive ...primer., If I was using Gillespie coating ( Alkyd enamel ) then I'd just topcoat right over the zinc primer

 

[135gmc]

Alodine is the perfect solution, except you are stuck buying it in buckets instead of quart bottles. Check with an auto body supply shop for aluminum conditioner. It seems to run about $ 15-20 per quart, and a quart can handle a lot of aluminum. You can also buy it on line as well.

SEM Company makes a self-etch zinc chromate primer in spray cans that is available at auto parts dealers. I've been using it for about 5 years and never had any paint failures.

 

[4x4 Forever]

Wash it well to get the oil/grime off, dry, use muriatic acid to etch, dry, apply zinc chromate primer, dry, apply your choice of primer that is compatable to the paint you are going to use, and paint.

That is what we do when painting any aluminum part used in the marine industry, works really well!.

 

[PropDr]

use muriatic acid to etch.

That will cause Hydrogen embrittlement and eventually lead to cracking.



Wash with soap and water, etch with alumaprep 33, apply alodine chem film, prime with zinc chromate or exoxy, and then top coat with your favorite color.



I'm surprised that people are recommending that you media blast a fuel tank. Assuming that the tank is used I would be very worried about static discharge causing an explosion. If the tank is new please disregard my babbling.