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Aluminum plate prep for painting

Saville

Well Known Member
Aluminum painting newbie here:

Ok so I have a roughly 1 foot by 8 inch 0.064 piece of aluminum that I want to prime and paint.

I plan on cleaning with acetone,

then BONDERITE C-IC 33 AERO/ ALUMIPREP 33

then alodine

then priming and then painting.

The piece has a few very light surface scratches/tool marks - nothing deep.

Question:

I planned on first scuffing the entire piece with the 3M Scotch Brite Red Hand Pad:

Is this a mistake?

Thanks!
 
Paint

Nothing you said was a mistake, but you can make it simpler.

You can skip the acetone since the alumiprep also acts as a cleaning agent
1. Lightly Scuff with scotchbrite while soaking with alumiprep 3-4 minutes (the alumiprep creates an acid etched surface similar to a "mechanical etching" that you do with a scotchbrite pad alone)
2. Rinse with clean water and immediately alodine
3. Alodine ~4 minutes
4. Rinse with clean water and blow dry
5. Wipe with tack cloth and use a wax & grease remover as needed
6. Prime according to directions
7. Paint according to directions
 
Last edited:
Surface prep

Nothing you said was a mistake, but you can make it simpler.

You can skip the acetone since the alumiprep also acts as a cleaning agent
1. Lightly Scuff with scotchbrite while soaking with alumiprep 3-4 minutes (the alumiprep creates an acid etched surface similar to a "mechanical etching" that you do with a scotchbrite pad alone)
2. Rinse with clean water and immediately alodine
3. Alodine ~4 minutes
4. Rinse with clean water and blow dry
5. Wipe with tack cloth and use a wax & grease remover as needed
6. Prime according to directions
7. Paint according to directions

Good prep instructions.
If you want a bit less environmental impact, substitute Bon Ami for the Alumiprep.
Alodine as soon as practical. Aluminum Oxide reforms pretty quick.
Please capture runoff. It's pretty bad stuff. I made a sluice to catch it and allow it to flow into a storage bin. Once it evaporated down to a gallon or less, I poured it into a strong botle and took it to haz mat disposal.
 
Make it even simpler:
- Clean with alumiprep using a red Scotchbrite. Don?t go crazy, just scuff the surface.
- Rinse well (a lot of water) and let dry. If the water does not sheet off, clean again.
- Prime with a good quality epoxy primer (the same day as cleaning).
- Top coat, keeping in mind the time limit from prime to top coat. For PPG DP-40 it is no longer than 24 hours.

Skip the alodine as the epoxy primer makes it redundant.

Carl
 
I prepared the aluminum similar to what you described in your post. I only used acetone if the panel is "greasy" from the various preparation steps.
I left most of the interior alodine and only prime and paint only a few interior area such as the cockpit because that is the part people are seeing. All the wing interior, most of fuselage interior are alodine only.
 
I prepared the aluminum similar to what you described in your post. I only used acetone if the panel is "greasy" from the various preparation steps.
I left most of the interior alodine and only prime and paint only a few interior area such as the cockpit because that is the part people are seeing. All the wing interior, most of fuselage interior are alodine only.

That's why I was thinking of using acetone first - to eliminate any grease from hands etc. Wasn't sure the alumaprep would adequately do that.
 
Simpler way that has worked for me.
Wash with Dawn
Sand with DA sander and 150 grit
Rinse
Degreaser
Prime with SPI epoxy primer
Top coat
This is what SPI recommends. You have to use their degreaser and no Alodine or wash primer under their epoxy.
 
Nice to see all the alternatives but I already bought my primer and paint so I'm using alodine.

And the original question was:

Is it ok to scuff the entire plate with #m red scotchbrite.

The answer seems to be "yes" with the added suggestion of dipping the scotch brite hand pad in the alumaprep.
 
That's why I was thinking of using acetone first - to eliminate any grease from hands etc. Wasn't sure the alumaprep would adequately do that.

I would certainly agree and not to contaminate your scotchbrite pad. I do use isopropyl alcohol as it is less aggressive in general, but acetone is likely more available these days. Just as an FYI, the solvent cloth has to be wet to remove stuff, not damp.

What are you doing with this piece? Also assuming it is 2024?

Is this a plate to go under your tires at OSH?
 
I would certainly agree and not to contaminate your scotchbrite pad. I do use isopropyl alcohol as it is less aggressive in general, but acetone is likely more available these days. Just as an FYI, the solvent cloth has to be wet to remove stuff, not damp.

What are you doing with this piece? Also assuming it is 2024?

Is this a plate to go under your tires at OSH?

This is a new cover plate I'm constructing to install a new fuel selector. I covered the design and material selection in another thread:

http://www.vansairforce.com/community/showthread.php?t=179791

You can see the old (crummy) installation in #1.

Then if you go to #13 and look at the 3rd design I listed that's the design I'm using. I have to paint both the blue coverplate and the green underplate.
 
Scuff

Nice to see all the alternatives but I already bought my primer and paint so I'm using alodine.

And the original question was:

Is it ok to scuff the entire plate with #m red scotchbrite.

The answer seems to be "yes" with the added suggestion of dipping the scotch brite hand pad in the alumaprep.

Yes. And don't worry about oils left behind with Alumiprep. It's a very strong acid. Wear gloves. You're more likely to contaminate the part after it's clean so switch to clean nitrile gloves.
 
OK I'm about to do this today, and I have another question:

So it's an 8"x12" plate. I want to paint both sides. So I assume that I should alodine both sides at the same time? Then hang the piece and paint both sides - at least a first coat - at the same time?

I figured that alodine and painting one side at a time would not work but I thought I'd check


Thanks.
 
Plate prep

OK I'm about to do this today, and I have another question:

So it's an 8"x12" plate. I want to paint both sides. So I assume that I should alodine both sides at the same time? Then hang the piece and paint both sides - at least a first coat - at the same time?

I figured that alodine and painting one side at a time would not work but I thought I'd check


Thanks.

If possible, alodine both sides. Once Alodined, the surface is theoretically stable from aluminum oxide formation so paint can be applied any time. Wipe with a solvent before spraying just to be sure.
 
If possible, alodine both sides. Once Alodined, the surface is theoretically stable from aluminum oxide formation so paint can be applied any time. Wipe with a solvent before spraying just to be sure.

What solvent would you suggest post-alodine?

My intention is to prime the piece as soon as the post-alodine water rinse is dry
 
Solvent

What solvent would you suggest post-alodine?

My intention is to prime the piece as soon as the post-alodine water rinse is dry

Maybe unnecessary then. It's one of those paint habits. Wipe with solvent then a tack cloth just before spray. A volitile solvent like lacquer thinner or acetone is commonly used. I prefer Kirker 600 Surface Wash.
 
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