mast corrosion - how serious? pic attached - SailNet Community

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Old 01-03-2012
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mast corrosion - how serious? pic attached

I recently bought a 1977 Tartan 34C in decent shape. But I just discovered some corrosion on the keel-stepped aluminum mast (see photo). It appears that the metal fitting of the pictured connector for the mast antenna had been touching the mast and together with some spray dripping down the mast resulted in galvanic corrosion.

How serious is this? Does it need to be fixed immediately? I am a bit worried that the corrosion is close to the mast step and that mechanical pressure in this region is higher than elsewhere on the mast.

What repair can be done, and how?
Thanks!
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mast corrosion - how serious? pic attached-mast_corrosion.jpg  
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Old 01-03-2012
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It does not look too bad.
I would watch it for cracks in the future. Keep it oil-wet in the meantime with WD40, or similar.
You might wish to put a wee sealant bead "weir" above it to divert future drips away from it.
Cracking is generally made worse by tension, and you really will not have any tension there.
Can you get a better close-up of the corroded area, perhaps using a mirror?
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Last edited by Rockter; 01-03-2012 at 11:08 PM.
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Old 01-04-2012
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Tough to tell from that picture but it looks like pretty severe pitting. Can you get the camera down further ? Do you have or can you borrow a pit gauge ?
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Old 01-04-2012
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It will take me a while until I can get out again and take another picture. But there is pitting which is very noticable when you feel over it.

Let's say if it has corroded to 1/2 of the mast thickness in that spot, what would that mean?
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Quote:
Originally Posted by tominny View Post
It will take me a while until I can get out again and take another picture. But there is pitting which is very noticable when you feel over it.

Let's say if it has corroded to 1/2 of the mast thickness in that spot, what would that mean?
1/2 would be pretty dramatic, I'd get a qualified rigger to look at it. It could be galvanic corrosion but it looks severe enough that it could also be stray current corrosion. I'd also check for that.
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Thanks, I'll look into that and see if I can find a way to test for stray current.

I assume in either case I will need to electrically isolate the connector from the mast.

Is this corrosion spot a severe safety risk? How can it be fixed without replacing the mast? Built an epoxy wrap around it to reinforce the area?
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Isolation is a must. If it is really severe, we are talking a weld repair andof course mast removal. But don't jump the gun do the other things I suggested first as I said it's a tough call from the photo.
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Are you sure it is corrosion? I can't see well enough in the pictures, but could it have been caused by that connector repeatedly swinging against the mast as the boat rocks at anchor? It does not seem that bad to me. There are plenty of places where the mast is drilled through to attach hardware without any serious loss of strength.
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Old 01-05-2012
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That antenna connection should be covered in self-amalgamating tape to keep moisture out, plus that will fix your galvanic issue at the same time!
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Old 01-05-2012
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The corrosion has almost certanly been cuased by the unsecured VHF conetion next to it, If you prevent this from touching the mast there should be no further corrosion.
The limited corrosion should not present any problems, Masts have holes in them for halyard exits etc without falling down. From the photo it looks like the loss of strength would be less than a rope exit.
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