Corrosion repair help!!!!

[Kristofer Duckett]

I am needing help for a corrosion repair in our near Fort Walton Beach, FL. I found corrosion in the cargo compartment on the right and left side wall where the seat hooks to the wall. It appears to be from dissimilar metals. Fortunately there is nothing on the skin and virtually no where else. There is still a lot of glue from the headliner but the corrosion is clear. Can this be fixed and is there someone close I can see? Thank you!

[Clarence Beintema]

You can repair the damage, it appears that the parts on the left side have corroded right through. You have a few choices, find used parts to install, find new old stock parts, or fabricate new based on old parts as a pattern.

There are plenty of Comanches being parted out, so used should not be a problem. The right side will require removal of the corroded areas to examine the metal. Buy yourself a copy of the FAA AC 43-13 from Spruce etc. it will be your guide line for the repairs.

Clarence

[Charles Schefer]

Kristofer, are you sure that is corrosion???? From the pictures it looks like old 1300L glue which is used to glue the headliner in place. When 1300L gets old it turns dark brown and while I am not 100% certain looking at your pics that just looks like old 1300L glue to me. I think you will find that old 1300L looks ugly but it's harmless and right underneath is zinc chromate primer on the inside skin.

To be sure you can get some MEL (methyl ethyl ketone) from your local Home Depot or similar hardware store and some rags. Put a little MEK on a rag and apply it to the old glue. When the glue turns dark like that it's very hard to get off. When using MEK please, please use a respirator and use gloves. Getting MEK on your skin soaks in and can cause liver damage. The fumes from MEK can be intoxicating and do other bad things - again wear a respirator and also try to keep the cabin ventilated with a fan.

You will also find that the MEK takes the zinc chromate primer off to some extent. When this occurs you need to re-prime those areas to protect the metal. You can buy zinc chromate primer from Aircraft Spruce. You may want to just confirm that this is old glue and not corrosion and then elect to leave it as is. The old glue is ugly but harmless. Getting all that old glue off and then re-priming is a lot of work (believe me I know from doing the anti-chaff strips on the nose cowl and also in doing a new door seal. I elected to get all the old glue off and re-prime but it was a LOT of work.

Good Luck,

- Charles

[Charles Schefer]

Kristofer, Looking at your pics again... are you talking about the dark brown areas as I commented on in my previous post or the whitish areas in the pics?

- Charles

[Kristofer Duckett]

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[Kristofer Duckett]

Charles-not the glue. There is definitely a good bit of old glue but if you look closer you will see the areas that are white-ish looking. These are the areas after I have sanded them down a bit too get all the corroded and corrosion spots away.

It's this something an A&P can do or will I need an IA? I was quoted $3000 from a local shop and am not very happy with that at all! I know several A&P's even a sheet metal specialist or 2 but if I need an IA that's where the problem comes in (and the bill)! She has been flying great and i still have a to do list and trying to avoid $3000 I don't have.

I need new auxiliary fuel bladders x2
Magneto overhaul x2
Prop inspection.
Transponder (just died a month ago )
Rotating beacon has grinding sound.

This corrosion is killing me!

[Andrew Foster]

What kind of transponder?
I have a kt 76a
Andrew

[Charles Schefer]

Sorry Kristofer, after I made that post I noticed the whitish areas and thought you might be referring to those. I think you will get varied opinions on this but if the repair constitutes a major repair under Part 43 then I think you will need an IA to return the aircraft to service and a 337 would need to be filed. To be clear, I'm not saying I think it is a major repair... I think you may find varied opinions on that.

Two thoughts...

Perhaps stating the obvious I would not cut corners on corrosion... There may be A&Ps that "repair it" inexpensively and tell you it's not a major repair but this may also be a case of "get what you pay for". The corrosion needs to be stopped and some areas may need to be strengthened an reinforced. In my book I'd call those major... On the other hand if it's largely just surface corrosion and light - you may have caught it early and simply removing the corrosion and painting those areas with zinc chromate may do the trick.

Before proceeding with ANY repair I think you should ask yourself - if this corrosion occurred inside the cabin then where else might there be similar corrosion? I hate to sound pessimistic but if you're in the FL area as I think you indicated you are and you've found this corrosion inside the cabin then I think it's likely there might be corrosion issues elsewhere. Before you spend $3K on this problem I'd pull some wing panels off, maybe take up the carpeting and look under the floor and perhaps in the tail cone and see if you see similar problems.

- Charles

[Kristin Winter]

Whether this is a major repair requiring an IA's involvement, or a minor repair, will depend on how the repair is made. Even if a major repair, it only requires an IA to make the final inspection and sign off. The work can be done by an A&P or someone under the supervision of an A&P. Replacement of parts is a minor repair. Splicing or installing doublers is likely a major repair in that area.

I would make sure that you know the limits of the corrosion before you make any other repairs to the aircraft. That is the most critical of all, and if it should turn out to be fatal, then you will not have spend money that would turn out to be wasted.

In addition to zinc chromate primer, you will need treatment the areas where you can just clean the surface corrosion. Alodine 1201 and Alumiprep 33 are the standards there. Spruce as all of the above.

I would first look at the parts brokers like KRN and Perferred Airports to see if new old stock parts are available. After that, it is salvage or fabrication. The channels might be difficult in that they may require forming blocks to create the parts.

All in all, $3,000 doesn't sound out of line for what the pictures showed, but if you have some A&P help who is experience in sheet metal, that is not an unreasonable way to go as there is a lot of grunt work there which you could likely do.

[Charles Schefer]

Kristen makes excellent points and regarding Alodine 1201 and Alumiprep 33 those are also hazardous to your health - handle with care. Alodine contains hexavalent chromium (Chrome 6) which is highly carcinogenic .

- Charles

[Kristofer Duckett]

Thank you all.

Charles - I have pulled most of all of the other panels and this seems to be the only place where corrosion is (there is very little on the vent openings and near the top of the windscreen). All of which seem to be from dissimilar metals from the new interior install. That I'm thankful for. I want to get it back in the air asap but the $3000 might prevent that.

Anyone use Corrosion X?

Any and all suggestions are very welcomed and much appreciated.

[Charles Schefer]

Sorry I have no experience with the Corrosion X product. I'd make sure anything you do is an approved solution under AC 43.13-1B -> http://www.faa.gov/regulations_policies ... ntid/99861

- Charles

[Charles Schefer]

Not that it will make you feel any better but I do feel your pain.... I have many times found a small project turning into a big expensive one...

- Charles

[Kristofer Duckett]

Charles - nice call on the MEK. Glue cleared now. Can actually see right down to the metal for the first time. Thanks! Now to get that corrosion looked at and fixed.

[Charles Schefer]

Kristofer - Nice work! I know the work involved in getting the old 1300L off! Looks like a much better view of the actual problem to solve now and it's hard to tell from a pic but it doesn't look nearly as bad now. Good luck and keep us posted.

- Charles