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prkaye

Well Known Member
I've often read people talk about "alodining" to provide corrosion protection. How does one "Alodine" a part? Is it a product you spray on, or wipe on, or what? Can you alodine parts to provide protection while in storage, or is alodine useless until you put the primer on as well?
Where is a good place to get the stuff?
 
Phil,
Alodine is typically applied by brushing alodine on a part, letting it sit, then rinsing OR dipping the part, letting it sit, then rinsing with water. The complete method is in the following document:

http://www.auf.asn.au/scratchbuilder/alodine1201.pdf

As far as I know, you *could* alodine a part while in storage, but I think that would be overkill. You would have to probably reallodine the part after you have prepped it.

I used alodine when I did my empennage. It is my least favorite part of priming, and I have since stopped doing it. I saw an email response from an AKZO Nobel representative that said to skip the alodine step due to how hazardous it is.

If you want to use it, Aircraft $pruce has it:
http://www.aircraftspruce.com/catalog/cspages/alodine1201.php

Also, I have heard that marine stores carry it. Try to get it locally if you can. If you get it shipped, you will get smacked with a steep hazardous material shipping bill. I also heard that it can be obtained in power form.

Good Luck,
 
I use it. If your careful the hazards can be minimized. Don't drink it, touch it or sniff it. I also believe you don't really need it but it will make your bird a little better.
 
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Alodine is a conversion coating that should be preceeded by a cleaning/etching with a mild acid like alumiprep. Alodine "converts" some of the surface material to a chromate and serves two purposes. One is to enchance corrosion resistance (an alodined part itself has about 2-3X the ASTM salt spray corrosion life as a bare part), the second is to provide a surface that the paint will adhere to. You should be able to purchase alodine and alumiprep at most aviation supply houses. For individual parts, use a plastic tank or tray to soak the items, then rinse off with cold water

For assembly of my 9A, I alodined and zinc chromated all non-clad parts made from angle as well as rear spars. Alodined all ribs, then chromated contact surfaces between ribs and skin. Alodine was applied to exterior before final paint.

From my own testing, I figure bare aluminum A/C, good for 25 years. Alodined interior contact surfaces 50 years, alodined and chromated, 100 years.

I believe there are a number of other pre-treatment materials that are available today. Unlike alodine and zinc chromate, they are non-carcinogenic.
 
prkaye said:
I've often read people talk about "alodining" to provide corrosion protection. How does one "Alodine" a part? Is it a product you spray on, or wipe on, or what? Can you alodine parts to provide protection while in storage, or is alodine useless until you put the primer on as well?
Where is a good place to get the stuff?
Click to expand...

Phil,
Yes, you can Alodine parts before storage. Are you contemplating Alodining all the parts prior to assembly? I would suggest you avoid that, as future drilling and dimpling will remove the Alodine from the areas where you most need it. Those areas are the edges and holes where you have no AlClading on the aluminum.
You can find a lot of excellent info on Alodining (and it's competitor Iridite 14-2) on EAA Chapter 1000's web site. See

http://www.eaa1000.av.org/technicl/corrosion/corridx.htm

I can also supply you with photos and text on how to do all of this, off line. You don't include your email address in your profile. If interested, left click on my user name at the top of this post. That will give you the link to my email address.
Charlie Kuss
 
So if I alodine my subassemblies with brush application before storing them, in several years when I pull the parts out for painting, do I re-do the alodine process before priming? Is there any risk that applying alodine now will lead to problems with priming/painting in several years from now?
 
Phil, I think everyone means not to alodine before you prep and drill the part. Most people work with the Al the way they get it (blue plastic and all)until just before riveting it together. So, after trimming, fitting, bending, drilling, etc is finished and you are ready to rivet the parts together forever, you insert the Aulmiprep, Alodine, Prime process here, if that's what you want to do. As a side note, the only step I do after priming is dimpling. That's becaue I cannot scuff the dimples very well when using alumiprep. And the 2-part primer I use stays on very well during the dimpling process.

Say, for example, you get your kit in August but know you won't be able to touch it before next July. Should you use any surface protection to help control corrosion? You could if you wanted to, but it's unnecessary, and you'll need to do it again anyway once the parts are fitted and drilled.

Once your subassemblies are finished, like your HS for example, most people just remove the plastic and leave the part in an environment where it would dry if it got wet. So, no plastic bags or anything that prevents evaporation. Could you go an extra step and alodine the parts for storage? Sure! but it's not necessary. When you get ready to paint, your will need to do a lot of surface prep anyway, Alodining then is more convenient.

And about priming with no surface treatment other than cleaning, you should at least scuff the surface VERY well to help the primer adhere. The Alclad surface is pretty slick and doesn't hold on to primers or paint very well. If you use self-etch primer, you should still scuff with scotchbrite first.

Hope this helps
 
Thanks Bart... maybe I should clarify what i'm thinking.
My completed horizontal stabilizer is being stored on the shop-side of my garage (smaller things like control surfaces are being stored in the house). When my wings are done, they too will be stored in the garage. As for priming, my approach has been to use a self-etchig primer only between mating surfaces.
Here's my fear... we use a LOT of salt on the roads in Ottawa in the winter. This gets tracked into the garage by the car. So I imagine the air in the garage starts to get quite salty by mid-winter. I'm afraid of my parts being stored there rusting away in this environment.
Two solutions: one is to store the car in the driveway all winter, but this will not make my wife happy.
My other thought was to alodone the parts I am storing. The HS has not yet been "closed-up" (one side of skin still open for insepction), so I could apply alodine to it before closing it up. I'd rather not go to the full extent of priming everything now... but thought maybe just the alodine at this stage would protect my parts being stored in the garage?
Thoughts?
 
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Warm fuzzies

I tend to err on the side of caution. You can:

A: Leave it to chance, hoping for the best. The plane would most likely be just fine as I believe most salt doesn't really evaporate, it must be carried with something else, like water such as salt-water spray. So, unless you are spraying the salt off your car and onto your airplane parts, it should not be of much concern.

B: Got the time, energy and supplies? Alodining will give you some warm fuzzies and a bit of extra assurance that things are going to be fine. Oh, and the plane will last theoretically twice as long, and your resale value MAY increase.

Cons to consider: Alodine is NASTY NASTY stuff. Very bad for you, so every precaution must be taken when working with it. You should also collect the rinse water and "slop" to be sure it doesn't get into the ground water. Some folks collect the rinse water and us it to make concrete door stops, boat anchors, post hole filler, etc. This supposedly prevents the chromates from leeching into the soil and is an approved disposal method.

FWIW, the US Air Force is moving away from Alodine to a more environmentally friendly surface protectant. I forgot what it is, but you could consider it as a safer alternative. I'm sure someone here knows.

It is dangerous and a big hassle. Read the EAA1000 info linked above, I found it to be VERY helpful.

When I use it, I wear a full body painters suit, nitrile and latex gloves, respirator and goggles, and am still extrememly cautious not to get any on me. Overkill? Maybe, but planes aren't much fun if you won't be around to fly them. Oh, and Alumiprep isn't too great either. It's a mild Phosphoric acid solution. Don't breathe it or get it on you. You'll need to Alumiprep prior to Alodining. Alumiprep 33 and Alodine 1201 is what you want. Some people use the Iridite powder. I understand it is basically a powder form of 1201, but since there's no water...shipping and handling are MUCH less.
 
Alodine pros/cons

I know there have been a lot of replies to this issue. Here is mine...I work in the commercial aircraft maintenance business (27 yrs worth) and specialize in structures..mostly metal. It is the required norm for the finish of virtually all aluminum alloys for the first step of protection and paint protection. Alodine is an oxidizer...sort of a controlled corrosive layer applied to clean metal.It forms a "conversion coating" which provides a sealing effect on the material and a good adhesion base for primer/paint. It only takes 30-60 seconds to do its job, then rinse away the rest. On alclad sheet, it seals the eges and holes,as the pure aluminum clad layer doesnt need it as much. As long as you are in a fairly well vetilated area and not breathing a sprayed mist, youll be fine doing an RV. The powdered form is for large tanks...I have some at my facility that would fit the whole wing in it! Be aware the dried residue on a rag makes it very flammable..its an oxidizer. If your worried about your stored wings and parts, bag them and put desicant crystal dry bags in with them, but I bet just keeping them a foot or so off the ground is all you need to do.
Good luck,
Bill E. RV-4
 
prkaye said:
So if I alodine my subassemblies with brush application before storing them, in several years when I pull the parts out for painting, do I re-do the alodine process before priming? Is there any risk that applying alodine now will lead to problems with priming/painting in several years from now?
Click to expand...

Phil,
I hope you do not intend to Alodine parts after they have been riveted together?? This is a not advised, as it is VERY difficult to rinse the AlumiPrep and Alodine out of the faying (contact) surfaces of parts which have been riveted together. You want to etch and Alodine each part individually, after dimpling all the rivet holes.
Let the Alodine dry at least 8 hours, then it's ready to prime.
Charlie Kuss
 
Less Toxic Alternatives

Hi Phil,

I think everything written here pretty much right on the mark. I was encourage you to just store the pieces in a dry place for now and now worry. I have had skins in my attic for a year or more with no problems.

As for alodine, it is a very toxic substance. As others have mentioned, hexavalent chromium is what the whole Erin Brockovich movie is about. There have been some interesting posts here on the Sanchem process that uses a permanganate solution to achieve the same thing. I have done most of my airplaine using that process and have been very happy with it. The residual can be decolorized and washed down the drain. Totally non-toxic.

Good luck with that.

Michael Wynn
RV 8 Unwrapping the fuselage kit
San Ramon, CA
 
I have always had a "rule of thumb" for myself regarding alodining parts. I always prime a part or whole airplane within 24 hrs. or alodining. Since I don't work on weekends I don't wash a plane on a friday. Can't say if there is any problem leaving alodined parts sit any longer. I was taught this way and it works for me. Hope this helps.

:)
 
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