Bolt Corrosion

[paul330]

Since I hadn't finished the wiring and didn't want to close up the panels, I thought I would get on with some of the systems work. About 9 months ago, I put in the flap drive. Now I come to do the rear seat floor pans, I find that I can't get them in with the flap drive tubes in place No matter, undo a few bolts and I can get them out.

Now to the point of all this. The bolts holding the various components of the drive together (passing 90deg through the tubing) are corroded. Not seriously, but enough to cause me concern. OK, they've been through an English winter in an unheated garage but they will get much worse in real use.

The surface coating has gone and there are signs of rusting - just surface stuff on the shafts where they are exposed. The tubes themselves (primed inside) are fine, as are the bolts that went through the plastic bearing blocks. Obviously, I will put in new bolts but it's likely to happen again. Worse, some of the control system has a similar arrangement

Is this minor corrosion normal on bolts? Is there any way to prevent it? And am I going to have to take apart all my steel control fittings and check the bolts? On the other hand, none of these bolts takes much load, so am I worrying unnecessarily? These are components that wouldn't normally be taken apart so perhaps everybody's are like it - you just don't know it.......

 

[aerhed]

You're not going to like this, but your best solution is to move to dry land. If your shop tools rust, so will your fasteners. Cosmoline? Par-al-ketone? LPS3?

 

[paul330]

Moving to warmer/dryer climes is the ultimate aim, but not possible right now As for putting the bolts in wet, all the primer would simply be scraped off getting it through the hole - although I could get some primer on in some locations. I'll have a think about the stainless steel option. No problem with the aluminium corrosion as these are steel parts. Isn't there an issue with SS being brittle and weaker?

I'm at a loss to understand this. I decided to do the step bolt replacement with an AN4 bolt and the AN3 bolts I took out in that location were fine. I'm away from home again now, but next time I am back in UK, I will check out the bolts in the aileron cranks.

How about spraying some WD40 around once the bolts are in place - or have I heard somewhere that WD40 is a bad thing?

 

[Bill.Peyton]

I would thoroughly coat all of your hardware with either ACF50 (http://www.aircraftspruce.com/catalog/cspages/acf50.php) or Boeshield (http://boeshield.com/). Both of these formulated coatings are designed to inhibit corrosion. I personally spray my Piper every year with ACF50. I live in St. Louis were it is humid all year, and after 20 years of owning this aircraft it still looks new inside.

 

[Aiki_Aviator]

I would thoroughly coat all of your hardware with either ACF50 (http://www.aircraftspruce.com/catalog/cspages/acf50.php) or Boeshield (http://boeshield.com/). Both of these formulated coatings are designed to inhibit corrosion. I personally spray my Piper every year with ACF50. I live in St. Louis were it is humid all year, and after 20 years of owning this aircraft it still looks new inside.

Don't know if I would use the Boeshield: Ref site FAQ:

Q. I would like to use it for cleaning my boat?s aluminum mast and spars but I am afraid it may discolor the finish. Can it be safely used on aluminum?
A. Rust Free? is phosphoric acid based and should not be used on aluminum, since it will remove the outer anodizing and could attack the base metal as well. For heavy oxidation on aluminum it is best to use an abrasive pad such as Scotch-Brite, with a little Boeshield? T-9 as a cutting oil and subsequent surface protector.

Not a good idea I think being phosphoric acid based....

 

[Phil]

Rust-Free and Boeshield T-9 are two different products with different purposes.

Rust-Free is an phosphoric acid that's designed to eat away corrosion. T-9 is designed to prevent corrosion from occurring. Both were designed by the big jet company Boeing - thus Boesheild.....

You're in good shape with Boesheield T-9. That's what I'd suggest too and I live in a very corrosive environment. Typically my unprotected tools have a layer of rust within 12-24 hours after using them. Boeshield does keep them looking new.

Phil

 

[Aiki_Aviator]

Rust-Free and Boeshield T-9 are two different products with different purposes.

Rust-Free is an phosphoric acid that's designed to eat away corrosion. T-9 is designed to prevent corrosion from occurring. Both were designed by the big jet company Boeing - thus Boesheild.....

You're in good shape with Boesheield T-9. That's what I'd suggest too and I live in a very corrosive environment. Typically my unprotected tools have a layer of rust within 12-24 hours after using them. Boeshield does keep them looking new.

Phil

Yep. I stand corrected. The FAQ on the site is badly organised and to make matters worse, I read it incorrectly without double checking. Seems they are completely different. Please disregard my previous statement.

 

[paul330]

Thanks for all the input.

Just to close the thread, I inspected some of the other bolts that pass through steel tubing and all are perfect. I am at a loss to understand why these particular bolts have corroded. None of my hardware or tools lying around the workshop show any inclination to rust It must be something to do with how these parts were handled but I am not aware of doing anything different.

I am going to replace them and coat with LPS3.

 

[Captain Avgas]

Now to the point of all this. The bolts holding the various components of the drive together (passing 90deg through the tubing) are corroded. Not seriously, but enough to cause me concern. OK, they've been through an English winter in an unheated garage but they will get much worse in real use.

All cad plated steel bolts that are in contact with dissimilar metals (eg aluminium) are best treated by an application of Duralac which will prevent galvanic corrosion caused by dissimilar metals in the presence of moisture. Not many RV builders know about Duralac but it is widely used by aviation maintenance engineers . One tube used sparingly should do a complete RV. I use it on all nutplates attached to aluminium as well.

Corrosion prevention during building is time consuming but not nearly as time consuming as reinstatement of corroded components down the track.

 

[David Paule]

2. Replace your bolts with stainless steel AN bolts (C suffix on the part number).

Generally, stainless steel bolts with the C suffix are not as strong as the normal bolts, so be careful there.

The various types of bolts have different properties so you need to read the spec carefully.

Dave