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Alodine competed components

wirejock

Well Known Member
How would you, or is it even possible, to alodine exterior skins such as the wings, tanks, fuse and control surfaces after they are complete? Can it be brushed or sprayed on somehow?
I am thinking about corosion protection under vinyl wrap so it's not just bare aluminum.

Please let's not argue the merits of primers or paints. I'm just curious how it would be done and thinking forward to final finish.
And the insides are 100% primed.
 
Yes, that is what paint shops do prior to paint. Brush or spray on, dwell, and rinse. Remember hexavalent chromium is carcinogenic and hazardous waste, so protect yourself and the environment accordingly.

Prior to treating, the normal procedure is to etch or scuff.
 
Do you have to scuff the aluminum before applying vinyl? If you don't, you would at least have the alclad for corrosion protection under the vinyl.
 
Alodine process

Yes, that is what paint shops do prior to paint. Brush or spray on, dwell, and rinse. Remember hexavalent chromium is carcinogenic and hazardous waste, so protect yourself and the environment accordingly.

Prior to treating, the normal procedure is to etch or scuff.
Question 1.
So you could build a wing or fuse rotisserie so the surface is relatively level and brush a coating on leave it the prescribed time then rinse?

Question 2
How do you protect the environment when you rinse it?

Question 3
Will a paint fume respirator work or is a fresh air system required? I have a good respirator and change cartridges on schedule.
 
Scuff

Do you have to scuff the aluminum before applying vinyl? If you don't, you would at least have the alclad for corrosion protection under the vinyl.

From what I've read, it adheres best when the surface is very smooth like bare aluminum so alodine would be a protection. No scuffing.
Primed surface is supposed to be sanded smooth.
Total rookie opinions. I know next to nothing. Just started my research.
 
Alodine

I alodined the inside of my fuselage by de-greasing with an etch cleaner and scotch brite pads, water rinse, then applied alodine solution with a spray bottle. Let it set for 10 minutes (don't let it dry), then clear water rinse followed by rinse with RO water followed by blow dry with compressed air to get most of the water off. I followed with a light primer coat, but understand that is not what you are doing. I would think the outside could be done similarly. There is no fume from Alodine, just mist from the spray application. I used a standard paint respirator. There were more fumes from the etch cleaner.
 
Prior to applying alodine the surface of the aluminum must be made water break free. You will need to scotchbrite the surface to achieve this. Alodine will not "take" to Alclad. The easiest way to get a good conversion coating is to place a paper towel on the surface then saturate it with the alodine. Be sure to smooth out any air bubbles and don't leave it on for too long or it will turn the aluminum very dark or "burn" the metal due to excessive oxidation. Applying alodine by brush or spray bottle only works when the surface has been prepped very well, and even then it sometimes hard to get the desired results since it tends to run off.
 
On other large projects I just used a normal hand spray bottle somewhat like a spray gun to apply the alodine and it works just fine. The hard part is ensuring it didn't end up in the waste water system.

I have seen other people brush it on too.
 
We use a "weed sprayer" at work for alodine.. You know the container you pump up with air and your favorite weed killer, and spray down the fence.

As long as you rinse out the container and pump after alodining, it'll work for a long time.we burn through one a month but we etch and alodine 3 to 8 airplanes a month. And we don't rinse out the container or pump.
 
Does Alodine continue to corrode joints when used on finished assemblies?

A fellow chapter member, who is a college engineering professor, is adamant that Alodine (Bonderite) is a strong acid that will continue to erode within the joints when applied to finished assemblies. He says it is only designed for individual parts and that, if used on finished assemblies, it will penetrate joints to the extent that it cannot be fully rinsed out. That?s apart from the nastiness of the stuff itself.

His argument sounds persuasive, especially when you see the TDS advises avoiding all metal containers. Yet I read here that this is SOP for aircraft painters. I see Homebuilt Help also has a Youtube on the procedure

I really want to use this method, having lately chickened out of wrapping over bare metal here in my maritime environment.

Does this argument have any credibility?
 
A fellow chapter member, who is a college engineering professor, is adamant that Alodine (Bonderite) is a strong acid that will continue to erode within the joints when applied to finished assemblies. He says it is only designed for individual parts and that, if used on finished assemblies, it will penetrate joints to the extent that it cannot be fully rinsed out. That?s apart from the nastiness of the stuff itself.

Does this argument have any credibility?

I just looked at the MSDS for Henkel Alodine 1201. It lists the pH as <2, so it is a very strong acid. I had always wondered about using Alumi Prep 33 (Phosphoric acid) on assemblies, but never realized that the conversion coating is acidic, too. Completely rinsing it from a completed aircraft would seem difficult, but many planes have been repainted this way. I've never heard of residual chromate damaging the structure, but it does beg the question.
 
My understanding, as someone with no recent hotel stays, is that 'conversion coating' means, in lay-bubba terms, 'a special kind of corrosion that creates a layer that prevents further regular corrosion'.

Like what happens in an imperfect way with pure aluminum, but is compromised by the alloying that makes 2024 so strong.

Charlie

(Bubba from Slobovia)
 
Prior to applying alodine the surface of the aluminum must be made water break free.
On the Space Shuttle they sanded with 320 grit wet/dry to get a "water break". Then etched with phosporic acid. Then flushed with copious amounts of water, then tested with Litmus paper strips to make sure no acid remained. Then Alodyne. I've used cotton balls to rub in the Alodyne for a nice, even straw color.
 
A fellow chapter member, who is a college engineering professor, is adamant that Alodine (Bonderite) is a strong acid that will continue to erode within the joints when applied to finished assemblies. He says it is only designed for individual parts and that, if used on finished assemblies, it will penetrate joints to the extent that it cannot be fully rinsed out. That’s apart from the nastiness of the stuff itself.

His argument sounds persuasive, especially when you see the TDS advises avoiding all metal containers. Yet I read here that this is SOP for aircraft painters. I see Homebuilt Help also has a Youtube on the procedure

I really want to use this method, having lately chickened out of wrapping over bare metal here in my maritime environment.

Does this argument have any credibility?

The acid keeps corroding/converting until neutralized with water. If the alodine finds it's way to a joint and the rinse is not thorough enough to get it out, it will continue to corrode/convert. This is a risk when alodining a finished plane. One must be cautious and thorough to insure no alodine remains after the rinse.

Once neutralized, there is no acid left to corrode, whether on a surface or in a joint. The converted material is not acidic and does not continue to corrode. It doesn't matter if the paint blocks the air or air is blocked due to a tight joint. The key is a complete neutralization.

And, yes, the surface must be free of any oxidation before alodine application. The oxidation layer forms in a few hours, so the surface must be etched, chemically or mechanically. The alodine will eventually eat through the oxidation, but not within the time specified in the instructions. Standardized dwell times are based upon a clean surface, with no oxidation.

Larry
 
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Alodine

A fellow chapter member, who is a college engineering professor, is adamant that Alodine (Bonderite) is a strong acid that will continue to erode within the joints when applied to finished assemblies. He says it is only designed for individual parts and that, if used on finished assemblies, it will penetrate joints to the extent that it cannot be fully rinsed out. That’s apart from the nastiness of the stuff itself.

His argument sounds persuasive, especially when you see the TDS advises avoiding all metal containers. Yet I read here that this is SOP for aircraft painters. I see Homebuilt Help also has a Youtube on the procedure

I really want to use this method, having lately chickened out of wrapping over bare metal here in my maritime environment.

Does this argument have any credibility?
Larry is correct.
Feel free to PM. I learned a lot on the project and happy with the results. Feeling much better about vinyl.
 
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Alodine large complete assemblies

So, here's what I have picked up and some of my remaining questions:
  • Alodine is a good strategy under vinyl. It reduces the chances of corrosion beneath the film, retains the weight advantage, provides a good key for adhesion and won't partially rip off when the vinyl is being re-done in the future. It is also a whole lot cheaper than priming.
  • Alodine won't work unless the surface if very clean, with little or no oxidisation. This probably means treating suitably sized surface areas and going straight through all of the chosen process on each area before proceeding to the next. It seems about 1-2 sq yd at a time might be a practical maximum to prevent drying of either Alimiprep or Alodine before rinsing. Is that a reasonable approach?
  • Both Alumiprep and Alodine are corrosive and need to be fully neutralised with water. The problem here may be the joints. How about power washing after a low-pressure hose rinse?
  • This stuff is very nasty (ask Erin Brokovich!) so you have to protect yourself from ingestion and even skin contact. I don't think just rubber gloves will cut it. What other/additional protective garments have people used?. Fumes on the other hand, do not seem to be a problem.
  • You can't let Alodine into the environment. You have to collect the rinse water. It can be left to reduce down through evaporation but then must be disposed of safely. One strategy picked up elsewhere is to mix the reduced run-off into concrete. I certainly have a lot of projects around the garden that need concrete. The question is how much run-off is likely to be generated. If it runs into hundreds of gallons then that is way beyond what a normal person could process.
 
Not to debate the effectiveness of either, but why not use Precote. No toxic waste disposal issue, and has been accepted by the military in some circles as alodine alternative. Sound to me like something what might serve your needs well
 
Not to debate the effectiveness of either, but why not use Precote. No toxic waste disposal issue, and has been accepted by the military in some circles as alodine alternative. Sound to me like something what might serve your needs well

IIRC Prekote is a bonding agent and has no inherent corrosion protection. The anti-corrosion performance is enhanced by the bond improvement of the subsequent coating. For a wrap I don?t know how that would work.
 
IIRC Prekote is a bonding agent and has no inherent corrosion protection. The anti-corrosion performance is enhanced by the bond improvement of the subsequent coating. For a wrap I don’t know how that would work.

However, if you are spraying on an epoxy primer, that is acting as the corrossion protection and the alodine treatment is really unnecessary. With an epoxy primer coating, the only real benefit the alodine is providing is improved adhesion. Alodine was far more important before urethane paints were introduced, with their impervious sealing nature. Acrylic and laquer paints didn't not seal out moisture near as well.

Most quality epoxy primers are desigend for DTM (direct to metal) application and have proven themselves highly effective in this application.

EDIT: sorry, just realized the OP was looking to vinyl wrap not paint. Another option to avoid the alodine hassles is to shoot the plane with epoxy primer after completion. You could do it in the garage, as you'll be able to easily wet sand the primer to get rid if dust nibs.

Larry
 
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