Corrosion in Aileron Push Pull tube

[hudgin]

Both of my aileron push pull tubes have corrosion on them. One is worse than the other. I seem to remember that 10 % of the thickness is the limit before it has to be replaced. Is that correct?

 

[bruceh]

Did you prime them? This tubing isn't alclad, so it needs protection from corrosion.

 

[Walt]

Both of my aileron push pull tubes have corrosion on them. One is worse than the other. I seem to remember that 10 % of the thickness is the limit before it has to be replaced. Is that correct?

10% is the generally accepted standard, but Van's doesn't actually spec that number in their manual anywhere so if you want an "official" answer you will need to ask Van's.

 

[hudgin]

They were primed with a good coat of zinc chromate. Where they havent corroded the chromate is changing color.

10% is good enough for me, I will change them out. Thanks

 

[ChiefPilot]

Both of my aileron push pull tubes have corrosion on them. One is worse than the other. I seem to remember that 10 % of the thickness is the limit before it has to be replaced. Is that correct?

Is this from the stick to the bell crank or from the bell crank to the aileron?

I'm wondering because one is a bit easier to inspect on a regular basis than the other...

 

[hudgin]

They corroded under the aileron boot at the net entrance into the fuselage.

 

[JonJay]

They corroded under the aileron boot at the net entrance into the fuselage.

Zinc Chromate is a sacrificial coating offering very little abrasion resistance. It makes sense that the boots wore through the coating defeating its ability to protect the base metal. All that was needed was moisture which probably soaked the boot allowing the moisture to sit for periods of time instead of evaporating.

The color change you are seeing in the chromate layer is it is corroding as it is supposed to. However, once it has converted, it no longer can inhibit and the corrosion will seek its next victim.

I would be curious to know what your boot was?
Regardless, a two part epoxy would protect this area better next time.

Good catch.

 

[hudgin]

The boot material is Naugahyde, is suppose flying in weather IFR captured moisture. The damage has occurred in only a one year time since last annual which is really fast I thought till I learned the tubes are not alclad. The new ones will get epoxy. They say if you learn something new you get to go home but then I'll never get to fly.