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Old 11-07-2009, 17:54   #1
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Filling Holes in Aluminum Masts

Hi All! I have removed a set of old mast steps (climbers) that were riveted and screwed into our aluminum mast in order to replace them with steps that have a different mounting footprint. I have considered both welding and filling the holes with epoxy filler. We are refinishing these masts anyway, so aesthetics aren't a problem. They will be repainted. Anyone have any experience with this?
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Old 11-07-2009, 18:01   #2
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I just install aluminum pop rivets in the holes when I move fittings.
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Old 11-07-2009, 18:45   #3
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I use a product called "Kneadit" - an epoxy putty that you knead till even texture then squeeze into holes - works well - even on an unpainted mast.
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Old 11-07-2009, 22:46   #4
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I would weld it if at all possible. I use those epoxy-sticks for temporary fills which works great (finish with wet finger).

We have done many changes on the masts and rigging and are planning to pull them somewhere in the US. Taking all the hardware off, blasting, welding, painting and putting the hardware back on with modern isolation stuff (teflon sheet etc.) is what needs to be done.

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Old 12-07-2009, 05:51   #5
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Why paint. It does no good, is expensive and can lead to pit corrosion where it gets scratched. Leaving it plain, or even better anodised, is better for longevity
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Old 12-07-2009, 06:08   #6
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How does one go about anodising an existing mast??
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Old 12-07-2009, 06:13   #7
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I'm with Robert - I bought my previous boat with a painted mast and the corrosion under the paint made it bubble and powder all over the place. I mechanically removed the paint and left it (apart from a polish) and it stayed looking geat for the several years till I sold it.
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Old 12-07-2009, 06:48   #8
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Electrolysis and water trapped under paint are the two killers for aluminium. Let the air get round it by not painting.

Look how long the Aircraft last in the desert scrapyards where the ali has been sandblasted clean
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Old 12-07-2009, 11:30   #9
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Quote:
Originally Posted by Robertcateran View Post
Why paint. It does no good, is expensive and can lead to pit corrosion where it gets scratched. Leaving it plain, or even better anodised, is better for longevity
Because I want a white mast ;-)

But I have seen some bare aluminium masts and they don't look good (pitting and spots with "powder"). Anodized is another matter and I might choose that if I would buy a new mast. I never heard of after-market anodizing of masts.

About the paint blistering: the paint is not the problem, it is the contact with a different metal in that area. You find this mostly around places where stainless hardware is attached to the mast. If it's nowhere near attached hardware, it is a surface contamination either from improper prep before painting or in the aluminium itself. The paint is not to blame and without paint the same problem will exist except there's no paint to blister.

Also: there's many different grades of aluminium and not all are good to withstand the marine environment without protection. I have no clue what they use for masts.

cheers,
Nick.
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Old 12-07-2009, 17:09   #10
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Thank you all for your input on this. I have considered leaving the masts au naturale, but I REALLY want white masts. Using TefGel and Teflon sheets eliminates a large source of corrosion in masts. I am aware that proper preparation is essential in mast painting. I am worried about welding weakening the masts, but TIG seems to localize the heating pretty well. Anodizing is out of the question, as the expense is close to that of a new mast. Pop rivets are a great idea, but between my mast steps, old sail track and such, I'll be covered in little bumps. Epoxy and Epoxy putty seem viable, but welding is still in first place... Thanks again, Chris
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Old 12-07-2009, 21:04   #11
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Why not use epoxy Metal-Weld or similar. It would be quicker, easier and cheaper than welding. Filling rivit holes is not structuralbut that stuff is pretty strong.
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Old 12-07-2009, 22:59   #12
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CVH: I just had a big half inch hole repaired by welding- can't even tell it was ever there but $$. I just painted my mast- pain in the butt but looks great. After 35 years you don't change her- she changes you. Oh, make sure you use that zinc primer, and then paint till the yellow goes away...
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Old 13-07-2009, 01:37   #13
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Quote:
Originally Posted by s/v Jedi View Post
Because I want a white mast ;-)

But I have seen some bare aluminium masts and they don't look good (pitting and spots with "powder"). Anodized is another matter and I might choose that if I would buy a new mast. I never heard of after-market anodizing of masts.

About the paint blistering: the paint is not the problem, it is the contact with a different metal in that area. You find this mostly around places where stainless hardware is attached to the mast. If it's nowhere near attached hardware, it is a surface contamination either from improper prep before painting or in the aluminium itself. The paint is not to blame and without paint the same problem will exist except there's no paint to blister.

Also: there's many different grades of aluminium and not all are good to withstand the marine environment without protection. I have no clue what they use for masts.

cheers,
Nick.
If most of a mast is sealed and only a little exposed, then oxidation will be concentrated in that area, no matter what you cover it with. Certainly fittings can exacerbate corrosion , but they are not the only problem. Aluminium is actually more reactive than zinc and relies on its dense oxidation layer to prevent further corrosion , so I am not sure if zinc primer really helps.
The process of anodising is fairly simple in principle. Put the aluminum in an acid bath-Sulfuric acid most common comercialy- and wack a big bit of current through it to encourage a thick oxidised layer, and then rinse thoroughly.
TIG welding the holes is certainly an option. It is also an option for cleaning out pit corrosion. I rebuilt an old mast one time when I was young and broke by floating out the oxidation while filling with good metal. I served me pretty well without any problems, though as the holes aren't a structural problem and you are going to decrease the long term viability of the mast by sealing it, you may as well bog it with epoxy. There will always be some stresses involved with the welding and possibly stress concentrations, so it is better without if not needed. (Someone can always have a lapse of attention and stuff up, blowing a great hole in the mast and then stuff around patching it , creating distortion- I used to repair aluminium runabouts and have had the occasional oops!)
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Old 13-07-2009, 04:33   #14
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We welded the old holes per the advice of the spar maker.
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