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Corrosion on Fuselage Concern!

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faklord
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Re: Corrosion on Fuselage Concern!

Postby faklord » Sun May 21, 2017 7:39 pm

I can't see any pictures but from the words in this thread:
If the corrosion is in/around the screw threads, this is due to the stainless screw/aluminium fuse interface. Use Tefgel (or similar) on the screws (This is an anti corrosion grease)
If the corrosion is elsewhere clean up as TomW suggests and ideally treat the area with something like this https://www.silmid.com/specialties/spec ... h-kit-1kg/

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Re: Corrosion on Fuselage Concern!

Postby plummet » Sun May 21, 2017 8:37 pm

Peter_Frank wrote:
Sun May 21, 2017 10:17 am
plummet wrote:
Sun May 21, 2017 1:08 am
Peter_Frank wrote:
Sat May 20, 2017 8:46 pm



If it is carbon/fiberglass then it is a slight corrostion from the screws, and it does not matter and wont get worse.

You could try to find a higher grade of stainless screws, so it wont corrode, but usually a slight corrosion does not matter, and for sure it wont destroy the carbon/glass :D

8) PF

That's the worse advice yourve given Peter!..

Corrosion will can only ever get worse unless you actively try to stop/reduce it.

PS Take a picture so we can see.

Why ? I am serious.

If you got carbon/epoxy and stainless steel, the galvanic corrosion hardly exists.
There are many in depth studies of this, mostly in aviation where the materials are used more often than in vessels but still with salt water (simulated seawater is used in most tests, as it is the "worst").

So the corrosion you got is on the screws usually, smearing a bit on the countersunk holes maybe.

This slight corrosion will not continue into the epoxy/carbon, thats why I would not worry about that - only change my screws if they are too low grade stainless steel.

He replied it was aluminium, so a totally different case of course, where it is a big problem indeed :wink:

8) PF
Galvanic corrosion is one form of corrosion you need to consider. With threads you need to consider crevice corrosion also. With stainless the question here is what is the CCT of 304 and or 316 in a marine environment?

Image

CCT = critical crevice corrosion temperature.

If left uncheck you can and will get crevice corrosion in threads with both 304 and 316 in a marine environment. Therefore you cannot disregard the corrosion. It time it will fail if left unchecked.

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Re: Corrosion on Fuselage Concern!

Postby TomW » Sun May 21, 2017 10:44 pm

Look at the OP's photo. The corrosion is at the head of the screws on the fuselage. Not the threads on the strut

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Re: Corrosion on Fuselage Concern!

Postby plummet » Sun May 21, 2017 11:40 pm

TomW wrote:
Sun May 21, 2017 10:44 pm
Look at the OP's photo. The corrosion is at the head of the screws on the fuselage. Not the threads on the strut
It's still a crevice. So the same theory still applies.
If there is a dissimilar metal between fuse and fasteners you have a combination of crevice and galvanic corrosion to consider.

Ps I can't see a photo.

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Re: Corrosion on Fuselage Concern!

Postby cglazier » Mon May 22, 2017 4:06 am

On a related note,
I am trying to help deal with a stainless steel screw that was so badly corroded into an aluminun mast that it got sheared off when the owner tried to remove it. Now we have part of a stainless screw imbedded in an aluminum mast.. Hopefully a machine shop can help or the mast is useless.

Note to foilers with aluminum mast or fuselage: do not leave stainless and aluminum parts in contact for months after salt water exposure. This owner actually took his foil apart but put the stainless screw back into the mast for storage.

:roll:
CG

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Re: Corrosion on Fuselage Concern!

Postby TomW » Mon May 22, 2017 10:49 am

Yikes. I'm glad I bought a carbon foil. It has aluminum fuse, but only 13 sessions.
No sign of any corrosion. I remove fuse from strut for storage.

CG that mast sounds like scrap, or how about cutting off the end?

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Re: Corrosion on Fuselage Concern!

Postby Blackrat » Mon May 22, 2017 5:39 pm

you should be able to tig weld onto the broken off bolt, the heat will also help loosen it up

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Re: Corrosion on Fuselage Concern!

Postby faklord » Mon May 22, 2017 10:16 pm

CG a screw extractor might do it (a sort of tapered left hand die - Google it). Hopefully the heat from drilling a pilot hole will help loosen it. However, to drill a pilot hole central to and in line with the broken bolt may be a challenge without some sort of jig.
Also, Prior to this operation I would soak the broken bolt In penetrating oil. Assuming the tapped hole in the mast is not blind, You could invert the mast (so broken bolt is at the bottom) and fill up the hole from the other end with penetrating oil and leave to soak, maybe even apply a bit of heat as well (hot air gun)

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Re: Corrosion on Fuselage Concern!

Postby Cefirmeza » Fri Jan 08, 2021 8:48 pm

Can someone help me suggesting how to treat this corrosion?
Attachments
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Re: Corrosion on Fuselage Concern!

Postby slide » Fri Jan 08, 2021 9:24 pm

on my landboard CKB lb3, the 3rd deck paul hartland made, showed carbon corrosion after many years of use. it was under the bolts that held the trucks on , on the top surface and it was like the washers where the bolts went tru had shunken into the carbon fibre over time , some kind of reaction to the sea salt/sand
i sent the deck to paul and he put another layer of carbon fibre on the top and when he sent me the deck back he included some white nylon washer's and
and that would stop the corrosion so there you go you need to stop the carbon metal contact

-we put it down to stainless washer's and their reaction over time to sea salt ,but i'm very happy to report this happened many years ago and is still in use fully restored, what i tend to do now with my carbon deck boards is as soon as i get home i give em a good clean with fairy liquid and a small toothbrush around the bolt/carbon area to try to remove any sea salt residue ,but it is impossible , but try to minimise it as much as possible,thats all you can do


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