alodine bare aluminum

[ohiohmmwv]

Anyone out there with experience using alodine to prep their bare aluminum? I used alodine on some bare aluminum plate pieces I cut to reinforce my rear late style seat bases. Cleaned bare aluminum with water, then alcohol, then soaked in alodine for 10 minutes, then rinsed with water and wiped down . There is very little coloring of the aluminum but the shine is gone. Did I do everything right? When I did the last step of rinsing was I suppose to wipe it down or just light rinse? Wiping down removed most of the coloring that was on it.

 

[jbayer]

No wiping after rinsing. Air dry. Generally use phosphoric acid to clean. Water break test, no water beading up, sheeting off only. Ten minutes is a little long. What grade of Alodine?
When you say "bare" do you mean bare, as in not Clad? Like 2024B, 7075B, etc. With these Alodining is for the whole part.
Or bare as in not primed/ painted?
Clad AL, as in 2024C, 7075C etc, will not take Alodine. With Clad AL, when you're Alodining, It's only for the cut edges/holes.

 

[ohiohmmwv]

It was 6061 aluminum plate, 1/8" thick. Alodine 1201. So you end up leaving all the alodine residue on the metal then? A gentle rinse doesn't take any off, a little pressure on the water will and a wipe takes almost all the coloring off. Why is it necessary to let the residue stay on there? Isn't it done physically etching the aluminum?

 

[Action]

something like this is a lot easier to use....

http://www.skygeek.com/henkel-alodi...MIo4ytjKbQ1AIVFIGzCh2U7gd5EAQYASABEgL6P_D_BwE

 

[ohiohmmwv]

something like this is a lot easier to use....

http://www.skygeek.com/henkel-alodi...MIo4ytjKbQ1AIVFIGzCh2U7gd5EAQYASABEgL6P_D_BwE

I'll definitely use one of those on the smaller areas.

 

[jbayer]

It was 6061 aluminum plate, 1/8" thick. Alodine 1201. So you end up leaving all the alodine residue on the metal then? A gentle rinse doesn't take any off, a little pressure on the water will and a wipe takes almost all the coloring off. Why is it necessary to let the residue stay on there? Isn't it done physically etching the aluminum?

Immersion time should most likely only be in the 1-3 minute range.
If you can find these MIL specs, take a look at them. MIL-C-5541- Chemical film application for Al, and AL alloys, and MIL-DTL-81706, CHEMICAL CONVERSION MATERIALS FOR COATING ALUMINUM AND ALUMINUM ALLOYS
If your using a non commercial product check the manufactures directions.
ALSO: Alodine 1200 series contains hexavalent chromium, BAD stuff. Use proper PPE, and dispose of waste properly.

 

[riderdan]

Trying to be helpful, not contrary...

If you're just going to paint over it, do you really need alodine? I think that zinc chromate primer is sufficient. I've taken automotive painting classes (for painting classic cars) and that's the first coat when we were painting aluminum body panels. If your Humvee isn't going to see an NBC environment, it doesn't really need CARC. If you're not spraying CARC, couldn't you just apply zinc chromate primer and then spray with whatever paint you're using? Or are you going for "correct"?

 

[ohiohmmwv]

I'm going for correct. Doing alodine on any bare patches, zinc chromate then carc. That's what the guys in the service with painting experience (hmmwv's and aviation) say is used. My misunderstanding is what alodine really does. Does it etch it or provide a primer coating? Or both?

 

[riderdan]

I'm going for correct. Doing alodine on any bare patches, zinc chromate then carc. That's what the guys in the service with painting experience (hmmwv's and aviation) say is used. My misunderstanding is what alodine really does. Does it etch it or provide a primer coating? Or both?

My understanding is that it's similar to the anodization process. Essentially it's creating a coating over the surface of the aluminum, but unlike anodization, alodine(ing?) doesn't require submersion or electricity. Alodine sometimes referred to as chromate conversion coating.

I've read that alodine is both protective and promotes adhesion... but it's almost always painted over.