Using Alumiprep 33 before Alodine

David Lynch · Post by **David Lynch** » Tue Nov 16, 2004 11:58 am

I am planning to Alodine and VariPrime the interior of the airframe. But the normally recomended cleaner is Alumiprep 33. The bottle states not to use on high copper alloy aluminum. 2024 has 4.5% copper, very high. Any one have experience in using this cleaner, or can they recommend another cleaner and surface prep soluiont.

Dan A · Post by **Dan A** » Tue Nov 16, 2004 4:10 pm

David, Alumaprep 33 is an acid etch for aluminum and it is used in conjunction with Alodine. You cannot get the Alodine to work on 2024 without first treating with the Alumaprep 33. Just follow the instructions for application. Don't worry. It will turn out fine.
Dan

Post by **Spike** » Tue Nov 16, 2004 4:14 pm

Hmm, I'm not familiar with "2024", is that just another name for the alclad that we primarily use in our kits ?

-- John

captain_john · Post by **captain_john** » Tue Nov 16, 2004 4:41 pm

2024 is the designation for the alloy we use on the skins, spars and ribs.

Alclad is a top layer of pure aluminum applied to the 2024 for corrosion protection.

Then you have the temper number, ie. T3. That is the flexability/brittleness measurement.

Hope this helps.

CJ

Post by **Spike** » Tue Nov 16, 2004 4:53 pm

Ok, I was on board then. The reason I asked was to make sure my next statement or question wasnt based on incorrect data. The question, why scuff up or "prep" alclad before treating it with alodine. The alodine is really needed where there is no corrosion protection. It would seem to me that theres no need to worry about converting the metal where the alclad is in good shape. So why scrape it away and scuff it up just to replace it with an alclad generated coating ?

-- John

captain_john · Post by **captain_john** » Tue Nov 16, 2004 5:28 pm

Ummmm, wellllll...

This is the stuff of primer wars. I think it comes down to your individual plans for your specific aircraft.

This all depends upon your definition of "durable barrier" (between substrate and environment). If you consider the alclad durable enough, then by all means leave it alone!

Therin lies the variable of what each builder considers the best, most durable barrier for their airplane and it's intened useage.

CJ

Post by **Spike** » Tue Nov 16, 2004 5:33 pm

Got it. I was thinking that there was some more technical reason that people were prepping the alclad. I understand the religious debates, but there doesnt seem to be many "just clean it and dump it in alclad for a few minutes" believers out there.

-- John

Guest · Post by **Guest** » Tue Nov 16, 2004 8:22 pm

I work around aircraft mechanics all the time. Some that are sheet metal specialist. They use prep 33 and alodine all the time. Then they put a 2 part epoxy primer on. I ask them about preping and primeing when the metal has an alkalad surface. They said 2 reasons. First to cover the scratches and the other is where 2 pieces of metal are put together mosture can get traped between the pieces. primeing is better than just the alcalad on the metal. Only time will tell who is right. Lyle

David · Post by **David** » Wed Nov 17, 2004 11:21 am

I only posted the question 24 hours ago and what a response. I guess metal prep is a real sensitive area.

David

spikescopilot · Post by **spikescopilot** » Wed Nov 17, 2004 5:08 pm

On some boards, it's religion and politics. Here, it's primer.

Heli-Wrench · Post by **Heli-Wrench** » Wed Nov 24, 2004 12:48 am

Being one of those previously mentioned Aircraft mechanics, I have to agree with using alumiprep/alodine.

A few suggestions about it's use:
Don't leave the part in the alumiprep too long. If the part is starting to turn dark, that's too long. You're eating up metal at that point.
Keep the part wet between alumiprep and alodine. After you rinse off the alumiprep, don't let the part dry off. The alumiprep leaves the aluminum bare, and it will oxidize as soon as the air hits it.
Don't leave the part in the alodine too long. It will come out with a "chalky" tone too it. Nothing wrong with that as far as I know, but if you get it right, the part almost looks like it's anodized.
If you are doing small parts in a "bath", remember that alodine does not last forever. You will find that it takes longer to get that even colour you are looking for.

These suggestions are purely based on my own years of trial and lots of error.

Allister.

aerial · Post by **aerial** » Thu Nov 25, 2004 8:43 pm

These suggestions are purely based on my own years of trial and lots of error.

So what about just epoxy primer on the "stock" parts in our kits?

captain_john · Post by **captain_john** » Fri Nov 26, 2004 9:51 am

I think that is really all you really need.

It is pretty much all I am doing.

CJ

tony · Post by **tony** » Sat Nov 27, 2004 1:00 pm

Ok, since someone else started this topic...

How are you guys disposing of your spent alumaprep and alodine?

Tony

RivetBangers.com

Using Alumiprep 33 before Alodine

Using Alumiprep 33 before Alodine

Boy what a response

Alumaprep & Alodine