Back in the day we used Zinc Chromate primer followed by a topcoat on aluminum. It's pretty hazardous to use, and there's probably better systems now. Alodine sort of replaces the anodizing that was originally on the aluminum before sanding. You need something to protect the raw aluminum from instantaneous corrosion when it's exposed to air.

Badsix's epoxy primed airplane didn't peel off, so that's a good test. Here's another vote for epoxy primer but apply it as soon as possible after sanding. It should seal as well as the Alodine would.

There's an A&P on this forum that answers questions like this, but he lives in Nevada and the Aliens may have abducted him by now...

that is very true!! this site is awesome. i’ve learned a ton just by reading as many posts as i can. thx

Sorry cant say for who or what I been working on BUT it keeps me busy.
I only get on here on my weekends any more.

After sanding Alum Use Alumiprep to etch it then seal with Alodine.
Either 1201 0R 1001, 1201 will leave a Gold tint to the metal 1001 is sorta clear after treatment. I always wash with soap & water & soft rag afterwards before top coating as the Alodine can and will leave a dust behind that will impair adhesion of Top coat of Primer.

FOLLOW instructions on Bottles or cans very carefully!!!! very important!!! Keep both treatments wet for the specified times in the instructions rinse both with water.
Its possible to Burn the Aluminum with the Alodine Watch the time its on the metal with a stop watch and keep it wet with a spray bottle works great.

https://www.aircraftspruce.com/catalog/ ... gJjmPD_BwE

https://www.aircraftspruce.com/catalog/ ... ne1201.php

If its on a Aircraft Im working or My own Aluminum project I always follow up Alodine treatments with "Zinc Chromate epoxy primer" But I have seen Aluminum left with Just an Alodine treatment for years with no corrosion.

Here is some I just did a quick google search for Zinc Chromate epoxy primer and it came up.
https://www.jamestowndistributors.com/u ... pid=336235
Just like any other product there are good ones and bad ones.
I been experimenting with a new one I like but I'm not giving recommendations on any products yet.

All that said You could could just take your chances sand it with 180 and just hit with Epoxy then paint over it who knows might out last you? but then again it could start bubbling up from corrosion I couldn't tell you. how long it would last.

I do know if you sand Aluminum you will remove the Protective Cladding that's on the metal from when it was made its not very thick.

YOUR THE ALUMINUM MAN! and don't get the Alodine on your hands, it will turn them yellow for about a week. many people will wonder why you have yellow hands.
Jay D.