Warbird Information Exchange

An exception or two to a rule does not invalidate the rule... Do any process incorrectly and you can mess something up.

Etching reduces the risk of future paint adhesion issues and resists further corrosion.

My information comes from the Douglas Process Specification used for commercial and military aircraft, and it applies to bare metal AND polished aluminum surfaces. A more common industry term is Colorless Conversion Coating (CC Coat).

I'm not talking the "good old days" of painting aircraft in your backyard with paint brushes, I'm talking about the industry accepted "correct" methods as outlined in the MIL-SPECs for commercial and military aircraft.

By the way, if you have ever seen the corrosion on an old static display aircraft painted with house paint, you would have second thoughts about using that method.

OK

I give.

Having been involved in well over 100 warbird restorations since the 1970's, I can't say I have ever painted an aircraft with a brush nor in my backyard. Frankly, I don't think I know of anyone who has.

I have worked on Gold and Silver Wrench warbird winners at Oshkosh and do know the difference between a good paint job and a poor one.

I was attempting to provide guidance to volunteers to help with the daunting task of working on a North Star. I also was atempting to point out that acid etching is not a must. Aircraft were painted for many decades (By Douglas and everyone else) without using this technique.

When it comes to painting aircraft, there are many things to consider. I know if I was to consider painting my aircraft (Currently polished) I would in no way consider acid etching. I can also say that 95% of aircraft that I have been involved in painting have been - it is an excellant method for paint prep.

Having now painted four static museum aircraft with 'house paint', I can say in my experiance it does not cause corrosion. These were all properly preped, primed with zinc chromate and painted. Some prefer the authentic warbird matt style finishes, this is a very effective method of acheiving this and meets museum guidelines for finishes. More likely corrosion is due to poor preparation and subsequent neglect which will occur no matter what finish you use.

I believe the volunteers working on the North Star project will be following the guidelines and policy of the National Aviation Museum. Likely acid etching would not be allowed under museum policy as most museum aircraft are restored using period techniques, materials and finishes. Because of this, I think it unlikely they will be painting it silver either!



Dave

Thanks gents for all of the great information. It is fantastic to hear about the different materials that may be used, along with the advantages and the pitfalls. I'll pass along this great info to the people in charge of planning and carrying out the work.

As for the museum process for polishing weathered aluminum... they may have one, but I doubt it. I will caution that I am not the voice of all knowning. However I can note that many of the aircraf the museum has have been delivered to the museum directly from operation where they were well maintained. They have also carried out some execellant restoration/rebuilds, but I don't think they have experience working with aluminum skinned aircraft that have sat outside for extended periods of time (~40 years for example). Project North Star does have a number of people on the team that come from the airline maintenance industry, and know maintenace procedures very well. However I suspect the polishing of the North Star will be somewhat of a chanllenge since even when airliners used bare metal finishes (rare to find that these days), they didn't go for more than a year with out a thorough polishing.

I'll keep everyone up-to-date on how it goes.

Mike

_________________
Mike R. Henniger
Aviation Enthusiast & Photographer
http://www.AerialVisuals.ca
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Do you want to find locations of displayed, stored or active aircraft? Then start with the The Locator.
Do you want to find or contribute to the documented history of an aircraft? If so then start with the Airframes Database.

Please do Mike.

And Chaps, you've both got a lot of sense in what you are putting across, but it isn't a black and white situation - so there's no need to throw paint! The input is worthwhile though.

Opening it out a bit, does anyone KNOW what any specific museum's policy on (re-)painting their historic aircraft might be? It's a big question, but any precise answers welcome. Vague too, as long as you say "I'm not sure but..."

Cheers

Like refacing the gauges in raduim, applying lead based paints, and using MEK as a solvent wipe...? They must have different regulations in Canada than here in the US (like asbestos mining).

It is a pleasure to have an august commentator such as yourself to contribute to this discussion. Clearly you are right.

Your method of just polishing through surface corrosion will work, but it will take a lot of time and create a lot of heat. My recommendation for acid etching will remove the corrosion deep down from within the corrosion pits in the metal, helping to minimize future corrosion, and probably give a suitable appearance by itself for their purposes. This is far less effort than polishing also. I included photos of a Convair airliner treated in this manner earlier.

From your statements about etching solution, one would think I was suggesting spraying the aircraft with battery acid...

Please also consider this my closing argument on the matter...

Perhaps we can get a professional aircraft painter to comment?

C'mon bdk,
You know better than that. Most of the world has different ways of doing things, and the USA isn't always the best.

If you are restoring an a/c to it's original spec, one of the baseline rules is to stick to the original materials as far as possible. Deviations from originality detract from the item's historical value as a historical artifact; it edges towards being a recreation or replica. If the museum has a primary responsibility to genuine artifacts (such as NASM, CanAv the Science Museum, England) then they will, as far as possible, use original materials. Hence my question.

Your valued points about how and why things are done by great organisations today are great. Don't, however, delude yourself that they are, therefore always and only the best way of doing the job. We both know that can't be true.

And don't chuck your teddies and pull your pram lid closed. I expect better of you.

Cheers,

James K

OK JDK, you brought me out of retirement!

Let's not forget that these aircraft are very old. The corrosion products are not original to the aircraft either, so they need to be eliminated and the aircraft preserved in the best way possible- within reason of course.

A few gallons of brightener and then some Alodine is far from an unreasonable suggestion, and I maintain that ths etching and conversion coating process will preserve the integrity of the aircraft far better than other methods (whether subsequently painted or not).

I only suggest that before a final decision is made, that a small experiment be performed so you can see for yourself.

http://www.aircraftspruce.com/catalog/cspages/alumprepaint.php

Hi Mike,

Contant the Swift Association in Tennessee, they will sell you a video on how to do exactly what you are asking about using Nuvite products. Or contact Nuvite at 1 (800) 394-8351 and they will put you in touch with the Swift Association. Nuvite products come in different grits and you will be able to bring it up to an amazing finish using a couple of different grits being applied with a circular buffer. If that isn't good enough, switch over to the Cyclone orbital polisher and you will be able to bring it up to a mirror finish. The better the finish the longer it lasts and easier it is to maintain. It's all in the surface finish. Therre is more surface area in a semi polished finish than a mirror polished finish which is why the mirror finish is more durable. If you magnify the two surfaces you will see more inperfections such as pits and very fine scratches in a semi polished finished and these imperfectiond hold dirt and moisture and promote corrosion. Which is easier to clean and stays cleaner, a new glossy paint job or an old faded dull one? Get the idea?

Glenn

Holy Cow! I just read my post and gave myself a "D" in spelling! I guess the new glasses aren't up to speed yet.

Glenn

Glenn,
A nice aspect of this forum software is that you can look at your message AFTER it's posted and if you see errors you can click on the "edit" button in the upper right corner of your message. You can then make any changes you want and submit it again. The old message is gone with the edited version in its place. I know from experience!

Dennis

HI WELL HERES MY TWO CENTS WORTH AS FOR PAINT THE AIR FORCE MUSEUM HAS SUPPLYED THE PAINT FOR THE A25-A PROJECT AND MUCH TO MY SUPRIZE ITS YOU GUESSED IT LATEX HOUSE PAINT EVERYTHING ON THE INSIDE HAS BEEN HIGH GRADE EPOXY WITH LOTS OF FLATENER!THEY CAN ONLY USE WATER BASED PAINTS ON THE EXTERIOR THANKS TO ALL OF OUR TREE HUGGING FRIENDS!! IVE TRIED IT ON A FEW SMALL AREAS AND THE LOOK IS PERFECT BUT IT SCRAPES OFF WITH YOUR FINGER NAIL BY THE TIME ITS DISASSEMBLED ,SHIPPED,AND REASSMBLED IT WILL LOOK LIKE ITS BEEN IN COMBAT FOR ABOUT 10 YEARS!!AS FAR AS POLISHING 3M MAKES A KIT OF SEVERAL SCOTCH BRIGHT DISCS THEN A FINAL POLISHING COMPOUND TO GET THAT MIRROR LOOK BUT IT ALSO REMOVES ALLOT OF THE ALCLAD COATING THAT HELPS TO PREVENT CORROSION.C+P AVIATION USED THIS ON THEIR NATURAL B25 AND IT LOOKS GREAT BUT TOOK SEVERAL WEEKS TO DO!!GOOD LUCK!! MIKE

Hey Mike, we buy polishing compound from the local CarQuest and it's good enough to buff the exhausts on the Focke-Wulf and we also did a few tests on the Pilatus, and it came out number 1.

Davem, my friend painted a glider with a roller, the job he did on it is top notch!

_________________
Olivier Lacombe -- Harvard Mk.4 C-GBQB

There is a fabric covering system out there I believe where the finishing coats are applied with a foam roller.

For reference, here's a shot of C&P's mirror finish B-25 taken last May. The 3M kit seems to produce great results.

_________________
Dan Johnson