Corrosion on yokes.

[DonMuncy]

When I got my 231, the left horn on the pilot's yoke was pretty corroded. I opted to just cover both yokes with leather. Now, the corrosion seems to be leeching through the thin leather. I am contemplating redoing at least the left one, or maybe both. Any ideas on how to treat the corroded areas before putting the leather back on.

[Guest]

Remove them, glass bead blast, etch with metal prep, alodine and prime.

Clarence

[DonMuncy]

17 minutes ago, M20Doc said:

Remove them, glass bead blast, etch with metal prep, alodine and prime.

Clarence

Jeez Clarence, that is the RIGHT way to do it. Any suggestions that don't involve removing the yoke(s).  

[M016576]

4 minutes ago, DonMuncy said:

Jeez Clarence, that is the RIGHT way to do it. Any suggestions that don't involve removing the yoke(s).  

I don't think there's really any other option- the corrosion needs to be addressed... and doing that without taking the yokes out of the aircraft would be very difficult... and messy... and risk severing the wires within.

seriously though: if you take them to an auto shop- cost will be maybe $100 bucks to sandblast and powder coat.  Aviation shop? .5 AMU minimum....

Edited December 30, 2016 by M016576

[jetdriven]

I think those yokes are magnesium and I don't think you're supposed to sandblast or beadblast magnesium, per AC43.13. This is a primary flight controlnandnpet corrosion spread hidden like that long enough, could cause an accident. 

 For future corrosion and prep, magnesium is a real PITA a deal with. But what I have found from redoing all three wheels on my airplane is that you strip them to bare metal with chemical stripper and then wash with soap water very thoroughly... water break test all that. then use PreKote surface prep  then BAKE the part in an oven at 250 for a couple hours. Then apply some type of chromate primer then epoxy primer and then urethane paint and then bake it again. Then  put your leather on.  Again magnesium is extremely anodic And is a real problem on Airplanes. But properly prepped and coated and  sealed it ain't no big deal

Edited December 30, 2016 by jetdriven

[DonMuncy]

Thanks guys. Not the easy answer I was hoping for, but facts are always better than guesses.

[zerotact]

I took my yokes to a powder coater.  $65 later I had two fresh looking yokes.  

[DonMuncy]

2 minutes ago, zerotact said:

I took my yokes to a powder coater.  $65 later I had two fresh looking yokes.  

It just seems to me that the cost/work to remove yokes and disassemble them prior to powder coating, cries out for a easier way. Maybe it isn't as much work as it seems. Can you, or anyone else who done this give us some insight as to the cost/work involved.

[rbridges]

maybe I'm being too simplistic, but couldn't you remove the majority of the oxidation via sanding and then coat the yokes with some type of rust paint?  If you're going to recover them, wouldn't this work?

[Hank]

34 minutes ago, rbridges said:

maybe I'm being too simplistic, but couldn't you remove the majority of the oxidation via sanding and then coat the yokes with some type of rust paint?  If you're going to recover them, wouldn't this work?

Rob, I don't think Rustoleum would stop corrosion on magnesium the way it can stop rust on mild steel.

[rbridges]

3 minutes ago, Hank said:

Rob, I don't think Rustoleum would stop corrosion on magnesium the way it can stop rust on mild steel.

I didn't realize the yokes were magnesium.  I thought they were good ole' USA steel.  

[Hank]

1 minute ago, rbridges said:

I didn't realize the yokes were magnesium.  I thought they were good ole' USA steel.  

Yours and mine are probably aluminum, but Don flies a modern K with the fat handles and lots of buttons and switches in both sides. All I have is a PTT and the PC disconnect button, but the PTT isn't inside the yoke up on top like his'n. 

[Marauder]

Don -- not sure if our modern style yokes are pure magnesium or a magnesium alloy. Either way, salt corrodes magnesium pretty quickly. If there is an alloy in the metallurgy of the yoke, you could be experiencing some galvanic effect causing the corrosion.

Is the corrosion worse on the left side of the yoke? Just curious since we typically fly with our left hand in the yoke and sweaty hands contain salt.


Sent from my iPad using Tapatalk

[ArtVandelay]

Magnesium burns, quite hot, doesn't sound like a good thing for an airplane?

[carusoam]

By the time you light the magnesium on fire, things have gotten too hot already... 

Best regards,

-a-

[DonMuncy]

Yes, the corrosion was worse on the left, and I thought it was a given it came from a sweaty hand.

[Guest]

Don,

To verify the yoke material you can sand an area clean and shinny, then apply a bit of Alodine 1201.  Aluminum with turn golden, magnesium will turn black.

Also there is no reason that you couldn't sand the yoke completely clean and treat/ paint in place.

Clarence

[M016576]

10 hours ago, DonMuncy said:

It just seems to me that the cost/work to remove yokes and disassemble them prior to powder coating, cries out for a easier way. Maybe it isn't as much work as it seems. Can you, or anyone else who done this give us some insight as to the cost/work involved.

It's really not a lot of work to pull the yokes, although a shop may charge you a couple hundred bucks, depending on their rates....I've helped to remove two sets of J model yokes in the past few years.  Takes about 30 minutes- maybe longer if the bolt securing the yoke to the shaft is a little soft and needs some TLC to remove.

The highlights....  use a small Allen wrench or Phillips driver to remove the two top plates.  Use a soldering iron to disconnect the switches in the top plates.  There should be plenty of wire slack, but if you're "short" clip the wire ties under the arms, and push the yoke in all the way, then feed a little extra wire through.  Once you've removed the top plates, it's time to remove the faceplate and disconnect the map light with the soldering iron.  After that, take the yokes off by removing the single bolt that holds them to the shaft AND the Allen set screw on the bottom of the yoke.  If you don't loosen the Allen set screw, the yoke will not come off... I promise.  Once the bolt and set screw is out, carefully feed the wires out through the center of the shaft.  

Re-assemble in the same way, opposite order.  careful if the wires in there have been strung for a while... they may be brittle.  Take all this with a grain of salt, too- I'm not an A&P.

[aviatoreb]

11 hours ago, M016576 said:

It's really not a lot of work to pull the yokes, although a shop may charge you a couple hundred bucks, depending on their rates....I've helped to remove two sets of J model yokes in the past few years.  Takes about 30 minutes- maybe longer if the bolt securing the yoke to the shaft is a little soft and needs some TLC to remove.

The highlights....  use a small Allen wrench or Phillips driver to remove the two top plates.  Use a soldering iron to disconnect the switches in the top plates.  There should be plenty of wire slack, but if you're "short" clip the wire ties under the arms, and push the yoke in all the way, then feed a little extra wire through.  Once you've removed the top plates, it's time to remove the faceplate and disconnect the map light with the soldering iron.  After that, take the yokes off by removing the single bolt that holds them to the shaft AND the Allen set screw on the bottom of the yoke.  If you don't loosen the Allen set screw, the yoke will not come off... I promise.  Once the bolt and set screw is out, carefully feed the wires out through the center of the shaft.  

Re-assemble in the same way, opposite order.  careful if the wires in there have been strung for a while... they may be brittle.  Take all this with a grain of salt, too- I'm not an A&P.

What albout all the wiring to the switches on the yoke - does that become an avionics shop job to remove the yokes?

[M016576]

18 minutes ago, aviatoreb said:

What albout all the wiring to the switches on the yoke - does that become an avionics shop job to remove the yokes?

The PTT switches use a tiny nut to secure them, the ones on the plate may require someone to solder them off... not sure if that's something we can legally do, even though it's very simple.

Edited January 1, 2017 by M016576

[RobertE]

I too have always been fearful of all the disconnecting/reconnecting of the wires.  I want a minimum of messing with those, in my case, 35 year old wires.  

So I've twice in 5 years manually sanded then sprayed the pilot side yoke.  Using flat black paint works to conceal the flaws.  To spray in place takes about 10 minutes of masking the interior with lightweight plastic sheeting.  Total job takes about 60 minutes.

 As to the source of corrosion, I think it's got to be from my sweaty hands since the copilot yoke has remained perfect for 5 years. No sign of any deterioration.  After about 3 years the first fleck of paint comes dislodged from the pilot side, not surprisingly where the yoke has my left hand resting on it continuously.

[FlyWalt]

20 hours ago, DonMuncy said:

Yes, the corrosion was worse on the left, and I thought it was a given it came from a sweaty hand.

Don, as cool as an aviator as you are, HOW could YOU ever have a sweaty hand? :-)

[DonMuncy]

1 hour ago, FlyWalt said:

Don, as cool as an aviator as you are, HOW could YOU ever have a sweaty hand? :-)

It was the previous owner  

And thanks. I really don't consider myself a cool aviator. I am one of the few (the only one?) pilots who does not consider himself to be a superior pilot. I consider myself adequate, and hopefully, safe; but still not a very good pilot.

[aviatoreb]

4 hours ago, M016576 said:

The PTT switches use a tiny nut to secure them, the ones on the plate may require someone to solder them off... not sure if that's something we can legally do, even though it's very simple.

Ah - well I am just asking - because I am not doing it myself.

I will be at the paint shop next month, and while its in paint, I am having yokes sent out for leather. 

[Guest]

It could be dis-similar metal corrosion caused by all the pennies you guys pinch in the CB club.

Clarence