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Posted by Don W on March 22, 2007, 10:41 am
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I've got an interesting problem to figure out how
to handle. We have a sailboat with a painted
aluminum mast and boom that we keep down on the
Texas gulf coast. Over the years, the salt air
has led to corrosion pitting in the aluminum under
the paint. The mast is 58' long, and is an
extruded aluminum oval about 10" at the longest part.
I would like to grind out the pits, and then fill
them in and sand them smooth while maintaining the
structural integrity of the mast. My thought is
to weld the pits back up with aluminum filler,
however there is a lot of material to conduct the
heat away.
Any thoughts on the best way to go about this?
Don W.
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Posted by Ecnerwal on March 22, 2007, 1:58 pm
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> I've got an interesting problem to figure out how
> to handle. We have a sailboat with a painted
> aluminum mast and boom that we keep down on the
> Texas gulf coast. Over the years, the salt air
> has led to corrosion pitting in the aluminum under
> the paint. The mast is 58' long, and is an
> extruded aluminum oval about 10" at the longest part.
...
> Any thoughts on the best way to go about this?
Replace it. The day it breaks will be a day you're in deep doo-doo; If
nobody dies you'll be lucky. A flagpole more than 1 flagpole's length
from anything valuable, perhaps - a mast, seems like a penny-wise,
pound-foolish choice.
--
Cats, coffee, chocolate...vices to live by
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Posted by Don W on March 23, 2007, 2:43 pm
Please log in for more thread options Ecnerwal wrote:
>
>
>>I've got an interesting problem to figure out how
>>to handle. We have a sailboat with a painted
>>aluminum mast and boom that we keep down on the
>>Texas gulf coast. Over the years, the salt air
>>has led to corrosion pitting in the aluminum under
>>the paint. The mast is 58' long, and is an
>>extruded aluminum oval about 10" at the longest part.
>
>>Any thoughts on the best way to go about this?
>
>
> Replace it. The day it breaks will be a day you're in deep doo-doo; If
> nobody dies you'll be lucky. A flagpole more than 1 flagpole's length
> from anything valuable, perhaps - a mast, seems like a penny-wise,
> pound-foolish choice.
That's two votes for replace it. These masts are
close to $10K new, and will cost $2K or better
used plus a bunch for shipping because of the
size. Plus there is no guarantee that a used mast
doesn't have any corrosion either unless you
personally inspect it before buying, and most of
the ones I've seen are in Florida, California, or
Louisiana so we're talking an airplane ride or a
10 hour drive each way. I sure hate to scrap the
old one just for a few corrosion spots.
I'll look at it closely when we pull it to work on
it, but I don't think it's scrap yet. There are
not very many visible corrosion bubbles, and they
do not go all the way through the base metal on
the ones that I have dug out with my knife. The
largest bubbles are about 1/2" in diameter. I'm
pretty sure that you could drill a hole that big
in the mast and not compromise the structural
integrity.
My primary concern right now is whether to fill
the few corrosion pits with aluminum (tig/mig), or
aluminum solder (o/a), or bondo. I'm thinking
that welding in aluminum or just using bondo wins
because of galvanic corrosion concerns around
dissimilar metals if I use the solder.
Don W.
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Posted by Bruce on March 24, 2007, 6:01 am
Please log in for more thread options On Fri, 23 Mar 2007 18:43:14 GMT, Don W
>Ecnerwal wrote:
>
>>
>>
>>>I've got an interesting problem to figure out how
>>>to handle. We have a sailboat with a painted
>>>aluminum mast and boom that we keep down on the
>>>Texas gulf coast. Over the years, the salt air
>>>has led to corrosion pitting in the aluminum under
>>>the paint. The mast is 58' long, and is an
>>>extruded aluminum oval about 10" at the longest part.
>>
>>>Any thoughts on the best way to go about this?
>>
>>
>> Replace it. The day it breaks will be a day you're in deep doo-doo; If
>> nobody dies you'll be lucky. A flagpole more than 1 flagpole's length
>> from anything valuable, perhaps - a mast, seems like a penny-wise,
>> pound-foolish choice.
>
>That's two votes for replace it. These masts are
>close to $10K new, and will cost $2K or better
>used plus a bunch for shipping because of the
>size. Plus there is no guarantee that a used mast
>doesn't have any corrosion either unless you
>personally inspect it before buying, and most of
>the ones I've seen are in Florida, California, or
>Louisiana so we're talking an airplane ride or a
>10 hour drive each way. I sure hate to scrap the
>old one just for a few corrosion spots.
>
>I'll look at it closely when we pull it to work on
>it, but I don't think it's scrap yet. There are
>not very many visible corrosion bubbles, and they
>do not go all the way through the base metal on
>the ones that I have dug out with my knife. The
>largest bubbles are about 1/2" in diameter. I'm
>pretty sure that you could drill a hole that big
>in the mast and not compromise the structural
>integrity.
>
>My primary concern right now is whether to fill
>the few corrosion pits with aluminum (tig/mig), or
>aluminum solder (o/a), or bondo. I'm thinking
>that welding in aluminum or just using bondo wins
>because of galvanic corrosion concerns around
>dissimilar metals if I use the solder.
>
>Don W.
>
As someone else commented, the spars are probably a 60-series aluminum
which is weldable. The question then is whether welding will harm the
mast to any significant degree.
It is quite common to see masts with welded on goose neck fittings or
winch mounts. My boat has both. Since it would be unlikely that the
mast was heatreated and then work hardened to a T6 condition after
the welding was done it would seem that a reasonable amount of welding
on a spar is a safe practice.
In my own case (40 ft. deck mounted mast) I stripped the paint and
then filled what pitting I found by welding. Then re-painted using an
etching primer and epoxy paint. To date it hasn't failed. As you quite
rightly noted ther are several drilled holes in the mast larger then
any of the corrosion.
If you do not TIG weld be sure that any flux deposits are completely
removed as the flux deposits seem to accelerate new corrosion.
Bruce in Bangkok
(brucepaigeatgmaildotcom)
--
Posted via a free Usenet account from http://www.teranews.com
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Posted by Don W on March 24, 2007, 10:08 pm
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> As someone else commented, the spars are probably a 60-series aluminum
> which is weldable. The question then is whether welding will harm the
> mast to any significant degree.
>
> It is quite common to see masts with welded on goose neck fittings or
> winch mounts. My boat has both. Since it would be unlikely that the
> mast was heatreated and then work hardened to a T6 condition after
> the welding was done it would seem that a reasonable amount of welding
> on a spar is a safe practice.
>
> In my own case (40 ft. deck mounted mast) I stripped the paint and
> then filled what pitting I found by welding. Then re-painted using an
> etching primer and epoxy paint. To date it hasn't failed. As you quite
> rightly noted ther are several drilled holes in the mast larger then
> any of the corrosion.
>
> If you do not TIG weld be sure that any flux deposits are completely
> removed as the flux deposits seem to accelerate new corrosion.
>
>
> Bruce in Bangkok
> (brucepaigeatgmaildotcom)
Thanks Bruce. Its good to hear that you were
successful. BTW, how much corrosion did you have
before you refinished it?
Don W.
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> to handle. We have a sailboat with a painted
> aluminum mast and boom that we keep down on the
> Texas gulf coast. Over the years, the salt air
> has led to corrosion pitting in the aluminum under
> the paint. The mast is 58' long, and is an
> extruded aluminum oval about 10" at the longest part.