Corrosion Repair

[mooneyspeed]

Hi there. I'm new to the forums and pretty new to Mooneys.   We bought our first plane this past April, a 1981 M20K, and have put about 25 hours on it so far. It just went down for annual in July as well as an avionics panel upgrade.   After we opened it up and took off some interior siding we found that a family of mice had moved in and proceeded to eat up much of the insulation and spread their business about the steel tubing in the cage and a bit into the left wing.   We figure they came up the left main gear sometime between its last annual and this one.  Couldn't smell a thing!!!

Corrosion is an issue and some tubes are going to need to be replaced and specialty welded back in.   Insurance has been great and is going to cover repairs.  The poor bird is scheduled for some NDT early next week.   

 

One of the options being presented to insurance,  which to my surprise they seem to be on board with, is to have the whole "birdcage" removed after being de-skinned, repaired, sand blasted and then powder coated.  Modern insulation and likely some new paint, or a betterment towards new paint, better wiring and some other addons to follow since this is all going on.

 

I'm looking for some expertise and opinion on the powder coating idea vs the standard treatment of green.  My concern is that it's a 35 year old airframe and even with a proper prep and coating that should some other crack/corrosion arise in the future it wouldn't be able to be detected anymore.  I've noticed its common for engine mounts to receive this treatment these days regardless of the higher stresses they endure.

 

I look forward to your replies.

[Raptor05121]

In your second photo, why is there duct tape over the inspection covers?

[carusoam]

Welcome aboard, MooneyS...

somebody this week has posted photos of the tubes that he is replacing as well.  Similar area for different reasons...

If interested in that situation, use the search function.  It should be easy to find...

 

while searching see what shows up related to powder coating limitations.  That process has had difficulty n the past because it may be able to hide too much...

I am only a PP.  this is not my area of expertise...

Best regards,

-a-

 

[ArtVandelay]

Looks like service bulletin 208 was never completed, if it had the insulation would be foiled backed. How bad is the corrosion, if you take some sand paper to it, is it just surface or does it run deep? How does the wing spar look?

[mooneyspeed]

We wont know the full extent of it until after Tuesday.  As per the insurance company's protocol they want ultrasonic testing done on the affected surfaces.  Those pictures were taken day of discovery for insurance before any cleaning and sanding was done to give them the "ugly" photos and let the adjuster see for himself.  The spar seems to be untouched at this point, but I will inquire as to the tape on the panels.

 

I'll try and find the posting that was mentioned of a similar situation

Thanks again

[1524J]

  On 8/5/2016 at 5:28 AM, mooneyspeed said:

We wont know the full extent of it until after Tuesday.  As per the insurance company's protocol they want ultrasonic testing done on the affected surfaces.  Those pictures were taken day of discovery for insurance before any cleaning and sanding was done to give them the "ugly" photos and let the adjuster see for himself.  The spar seems to be untouched at this point, but I will inquire as to the tape on the panels.

 

I'll try and find the posting that was mentioned of a similar situation

Thanks again

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The inspections panels in the rear seating area are supposed to be taped. I think mine had foil backing similar to tape used in HVAC ducting.

[Guest]

You should be using SB M20-208B as your guide.

http://www.mooney.com/en/sb/M20-208B.pdf

Clarence

[Bob_Belville]

I'm surprised to learn that this type damage is covered by insurance.

[N231BN]

I would stay away from powder coat. Proper prep and a good epoxy primer is a time-proven coating. If Mooney had used that instead of Zinc Chromate on the earlier airplanes you wouldn't be replacing any tubing.

[Yetti]

Someone who knows protective coatings will chime in, but my understanding is powder coat and spray are pretty much the same except spray has a carrier that evaporates(acetone)  powder coating the medium is melted together with heat.  Powder coating is harder to do properly.

Duct tape was used extensively to seal the cabin  I think per SB208.   Duct tape can hold water when it deteriorates.  You get pretty good with the foil tape after redoing all the places.

[jetdriven]

Powder coating is heavier than paint and can hide cracks.  

I fail to see how you are going to be able to remove the steel frame from the plane and do all this on a rotisserie, Becuase it would involve disassembling the plane so thoroughly as tk not be economically viable.  I think most owners get repairs by having sections TIG welded in place 

[Yetti]

and most of that rust is from leaky windows....  The mice did not help things.  What is crazy is I thought all models past the Fs were factory enamel paint on the tubes from the factory... and yours is a K 

[ArtVandelay]

  On 8/5/2016 at 4:01 PM, Yetti said:

and most of that rust is from leaky windows....  The mice did not help things.  What is crazy is I thought all models past the Fs were factory enamel paint on the tubes from the factory... and yours is a K 

Nope, my 78J is zinc chromate, I believe they switched in 88.

[TheTurtle]

insurance covers corrosion?  S*** if I had known that I wouldve bought the mouse filled G model I was looking at originally

[mooneyspeed]

  On 8/5/2016 at 5:08 PM, TheTurtle said:

insurance covers corrosion?  S*** if I had known that I wouldve bought the mouse filled G model I was looking at originally

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Yes! While the policy didn't list vermin or anything specific like that, they are covering this under the External Damages clause.

[mooneyspeed]

  On 8/5/2016 at 2:45 PM, jetdriven said:

Powder coating is heavier than paint and can hide cracks.  

I fail to see how you are going to be able to remove the steel frame from the plane and do all this on a rotisserie, Becuase it would involve disassembling the plane so thoroughly as tk not be economically viable.  I think most owners get repairs by having sections TIG welded in place 

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I can't imagine it being approved to go that far myself.   I'm expecting spot repairs on the sections requiring replacement.  My sentiments exactly on powder coat and cracks.  The shop figures the overall weight difference shouldn't exceed 5 lbs if we do decide on that.  Lighter is better in my opinion. At any rate we'll have the newer style insulation, a through SB 208 completed and an easier time with the avionics install.

Here's what it looks like after some skins have been removed and cleaning is complete.

[MB65E]

Wow, looks like you are in good hands. 

-Matt

[Guest]

It must be amazing powder coat if it can hide a crack. Sounds like it would be better than welding, just powder coat it!

Clarence

[jetdriven]

It doesn't hide a broken weld where the pieces Can move,  but will skin over a crack that's not opened up. 

Edited August 6, 2016 by jetdriven

[N601RX]

Maule powdercoats both their airframes and engine mounts. 

[jetdriven]

I can see the value of that if it's new parts and the whole thing goes into the oven at once and it's controlled.  I don't see that here with a steel tibe fuselage sitting on a wing with Windows in it.   And I have chipped powered coating off steel where it was all rusty underneath and looked perfect until you start digging.  So there's that risk. 

Edited August 6, 2016 by jetdriven

[MB65E]

With my kids, I've seen some really Nasty corrosion under playground sets. The powder coating can be like a candy shell, while the tube underneath will be dissapearing. Extreme example, and not 4130 steel, but you get the point. 

The mil spec epoxy etching primer is great!!

-Matt

[Cyril Gibb]

  On 8/5/2016 at 9:37 PM, mooneyspeed said:

Yes! While the policy didn't list vermin or anything specific like that, they are covering this under the External Damages clause.

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Not trying to open a can of worms, but this plane clearly didn't have the corrosion SB performed. 

If this is true then getting a thorough PPI is not necessarily a good idea.  Better to find corrosion after the insurance is in place assuming you paid a lowball price if corrosion was suspected.

[mooneyspeed]

  On 8/6/2016 at 3:22 AM, Cyril Gibb said:

Not trying to open a can of worms, but this plane clearly didn't have the corrosion SB performed. 

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That's  definitely seems to be the case here.  Fortunately we were able to catch this sooner rather then later and can go forward with everything up to spec.   The annual was proceeding fine right up until we found this.   Its low time (1800 hrs), was always hangared and the engine was just overhauled and zero timed 60 hours ago.   Thank goodness the GTN 650 and Aspen 1000 didn't go in first!  Otherwise they might be up for grabs in a write off situation.

 

Thanks again for your input.   Its going to be a thorough education on my plane.

[PTK]

Just curious, was a prepurchase inspection performed? SB208 is very well known among the Mooney speaking population and very easy to check compliance.