Surface Corrosion Must Go, Now!

[RoundTwo]

I’m going to be dealing with correcting surface corrosion to a somewhat significant extent. Most spots are sub-quarter size, but there are lots of them. The areas around the wing root fairings are especially bad and I have one headless rivet there. Ive attached several pictures below. I think the fairings will need to come off to ensure nothing has gotten started behind them.

I’ve spoken to a reputable paint shop and their method is a brass coated wire wheel, which I’ve been taught is bad due to left behind embedded steel fragments leading to further corrosion.

I have a compressor, pressure pot and several different grades of virgin glass beads I could use but feel that may be too aggressive for widespread use.
Soda blasting is where my mind is going but web research opinions seem mixed on soda as a valid means for corrosion removal. It seems that it is fine for paint removal but some have said it isn’t great for getting out all of the corrosion. Maybe a hybrid approach of soda for spot paint removal followed by beads for the actual corrosion removal.

I’ve used Nyalox brushes before and it worked pretty well, but is slow and like any wheel, difficult to easily get into sharp corners.

Any tips, tricks and techniques you’ve had success with would be greatly appreciated.

[Guest]

3M Sotchbrite pads, Alumiprep, Alodine, epoxy primer and paint.  Never a steel wire brush.

[Jsno]

M20Doc is 100% right on the above posting

[Shadrach]

Is that original paint? Is it possible that the stripper from a previous paint job was not fully removed.

[RoundTwo]

4 minutes ago, Shadrach said:

Is that original paint? Is it possible that the stripper from a previous paint job was not fully removed.

All original 1988 paint. Overall in good condition with noted exceptions.

[RoundTwo]

35 minutes ago, M20Doc said:

3M Sotchbrite pads, Alumiprep, Alodine, epoxy primer and paint.  Never a steel wire brush.

I assume the paint shop likes the brush because it’s aggressive and saves THEM time. 

[Steve0715]

Only in the white?  Orbital sander with a soft backup pad?

[RoundTwo]

Just now, Steve0715 said:

Only in the white?  Orbital sander with a soft backup pad?

Surface corrosion is confined to the horizontal surfaces mostly likely from salt-laden air settling. Vertical surfaces may have some small spots but I didn’t notice them. 

[Guest]

1 hour ago, RoundTwo said:

Surface corrosion is confined to the horizontal surfaces mostly likely from salt-laden air settling. Vertical surfaces may have some small spots but I didn’t notice them. 

This might be helpful

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43-4B.pdf

[RoundTwo]

2 minutes ago, M20Doc said:

This might be helpful

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43-4B.pdf

It’s a rainy day here in Georgia so perfect time to read this. Thank you.

[carusoam]

RT,

Pay extra attention to the headless rivet…

That can be a sign of corrosion between the two pieces of sheet metal.

The expansion of corrosion in the restricted space is strong enough to tear the heads off rivets.

+1 for getting a jump on this corrosion challenge early on!

PP thoughts only, no sheet metal experience at all…

best regards,

-a-

[RoundTwo]

1 minute ago, carusoam said:

RT,

Pay extra attention to the headless rivet…

That can be a sign of corrosion between the two pieces of sheet metal.

The expansion of corrosion in the restricted space is strong enough to tear the heads off rivets.

PP thoughts only, no sheet metal experience at all…

best regards,

-a-

This is the only decapitated rivet I saw. A corrosion sandwich is why I’m planning on removing the fairings. It looks like someone attempted a topical application of silicone to seal that gap.

[RoundTwo]

1 minute ago, bluehighwayflyer said:

That looks like filiform corrosion to me.  It is usually caused by poor surface prep prior to painting, but it is certainly aggravated by high humidity and other adverse environmental factors.  Once it is set in it can be really hard to permanently remove.  Proper surface prep, as set forth above by @M20Doc, is critical.  If it is as widespread as it appears a complete strip and repaint by a reputable shop might be the best course of action.  

Yes, it is filiform and there are plenty of places on upper surfaces that need attention.  However, one of the top paint shops, that I won’t mention, uses brass coated wire wheels to clean it off and that is a no go for me. I will be implementing a cleaning process that is ferrous-free and that’s why abrasive blasting is my first intended approach. 

[RoundTwo]

13 minutes ago, bluehighwayflyer said:

Yes, @jetdriven has documented here several times that a lot of paint shops that achieve beautiful, if not long-lasting, results often use really terrible and sometimes actually destructive techniques.  Caveat emptor applies big time.  The best way to know what you are getting is oftentimes to do it yourself.  Good luck!

It’s going to get a new paint job in the not too distant future but I’ll take care of the known spots myself.

[Fly Boomer]

2 hours ago, RoundTwo said:

This is the only decapitated rivet I saw. A corrosion sandwich is why I’m planning on removing the fairings. It looks like someone attempted a topical application of silicone to seal that gap.

In your initial tranche of pics, some showed gray patches that did not look like aluminum.  What am I looking at?

[RoundTwo]

3 minutes ago, Fly Boomer said:

In your initial tranche of pics, some showed gray patches that did not look like aluminum.  What am I looking at?

I believe that is just tarnished surface from being exposed, but it’s all aluminum.

[Pinecone]

There are brass wire (the whole wire is brass) available.

Also Scotch Brite wheels to have no metal, but not doing hand work.

[Huckster79]

I'm new here, and don't yet own a Mooney.  I'm currently a Cessna 140 owner, and I didn't have corrosion to deal with, but I did strip out the entire interior that had been glued to the interior of my cabin and they glued the living crap out of it.  Scotch brites did a great job getting me to aluminum, and specifically the ones I bought on Amazon for my Dremel... When I did the interior I went through 100s of them, they come in a bag of 50-100.  They don't last long if there's any corner or object you're going around but do a bang up job fast without the sin of using a steel wheel... I'd highly suggest them vs doing it by hand with a scotch brite...  They were a real time saver and did a great job.  Then etch, Aldine and epoxy primer.... 

[Guest]

Scotch Brite roloc come in flat discs and bristle variety’s in many different grits.

[Steve0715]

With a battery powered Dremel, that might be a very efficient tool for getting down to bare aluminum.

[Huckster79]

These are the ones I used... I couldn't imagine doing what you're about to without a couple hundred of these babies on hand... 

 

[Mark89114]

so when we have this corrosion on the seams, does it creep underneath the seam?  That would be my bigger concern.  Easy to get the stuff on the top.  Or do we just accept it for what it is and move on?  

[RoundTwo]

4 minutes ago, Mark89114 said:

so when we have this corrosion on the seams, does it creep underneath the seam?  That would be my bigger concern.  Easy to get the stuff on the top.  Or do we just accept it for what it is and move on?  

 

45 minutes ago, Huckster79 said:

These are the ones I used... I couldn't imagine doing what you're about to without a couple hundred of these babies on hand... 

 

My current plan of attack is soda blasting. If that doesn’t produce desired results, then glass beads. Beyond that rotary tools will be utilized with whichever implement(s) is/are needed.

[RoundTwo]

6 minutes ago, Mark89114 said:

so when we have this corrosion on the seams, does it creep underneath the seam?  That would be my bigger concern.  Easy to get the stuff on the top.  Or do we just accept it for what it is and move on?  

That’s the $64,000 question. There aren’t many near lap joints and the worst one is on the roof by the door. It’s hard to believe it hasn’t made its way under there. Like many medical procedures, we’ll do what we can at first and then it will be watchful waiting to see if it was successful.

[Guest]

On 3/14/2023 at 9:34 AM, RoundTwo said:

 

My current plan of attack is soda blasting. If that doesn’t produce desired results, then glass beads. Beyond that rotary tools will be utilized with whichever implement(s) is/are needed.

I wouldn’t suggest glass beads on thin aluminum skins.