Aluminum and...what?
 

The mast is on sawhorses. I inspected the spreaders. I liked what I saw.
Aluminum tubes going from round at the shroud end to oval at the mast, with
really sturdy mounts.

Here's the problem. The shroud end has an aluminum plug with a groove to accept the
shroud, then there is a cap to retain the shroud in the groove. The plug and
cap were connected using two stainless screws. Guess what? The corrosion
was so bad I had to hacksaw stuff to get them apart.

I'm having the machine shop make new plugs and caps, but I'm at a loss
as to how to secure the cap to the plug, to say nothing about how to secure
the plug into the spreader tube....without getting them chewed up again.
Bronze screws, if I can find them?

Any hints? Nigel Calder, you read this newsgroup? lol

Thanks,
Norm B

On Wed, 29 Jun 2005 20:22:15 -0700, engsol wrote:

The mast is on sawhorses. I inspected the spreaders. I liked what I saw.
Aluminum tubes going from round at the shroud end to oval at the mast, with
really sturdy mounts.

Here's the problem. The shroud end has an aluminum plug with a groove to accept the
shroud, then there is a cap to retain the shroud in the groove. The plug and
cap were connected using two stainless screws. Guess what? The corrosion
was so bad I had to hacksaw stuff to get them apart.

I'm having the machine shop make new plugs and caps, but I'm at a loss
as to how to secure the cap to the plug, to say nothing about how to secure
the plug into the spreader tube....without getting them chewed up again.
Bronze screws, if I can find them?

Any hints? Nigel Calder, you read this newsgroup? lol

Thanks,
Norm B

Do not dispair. Corrosion is well understood.

Aluminum, titanium, and more exotic alloys are used extensively in the
aircraft industry. They use thread coating pastes to prevent corrosion.

Use your favorite search engine to search on "aluminum corrosion thread
coatings". I use google.

You can use Tef-Gel. See at: http://www.tefgel.com/

"Anchor" wrote in message
.. .
On Wed, 29 Jun 2005 20:22:15 -0700, engsol wrote:

The mast is on sawhorses. I inspected the spreaders. I liked
what I saw.
Aluminum tubes going from round at the shroud end to oval at
the mast, with
really sturdy mounts.

Here's the problem. The shroud end has an aluminum plug with
a groove to accept the
shroud, then there is a cap to retain the shroud in the
groove. The plug and
cap were connected using two stainless screws. Guess what?
The corrosion
was so bad I had to hacksaw stuff to get them apart.

I'm having the machine shop make new plugs and caps, but I'm
at a loss
as to how to secure the cap to the plug, to say nothing
about how to secure
the plug into the spreader tube....without getting them
chewed up again.
Bronze screws, if I can find them?

Any hints? Nigel Calder, you read this newsgroup? lol

Thanks,
Norm B

Do not dispair. Corrosion is well understood.

Aluminum, titanium, and more exotic alloys are used
extensively in the
aircraft industry. They use thread coating pastes to prevent
corrosion.

Use your favorite search engine to search on "aluminum
corrosion thread
coatings". I use google.

Go see your favorite electrician and get some "gray stuff' that
they use in electrical boxes when attaching aluminum cable.

Leanne

On Wed, 29 Jun 2005 20:22:15 -0700, engsol
wrote:

Here's the problem. The shroud end has an aluminum plug with a groove to accept the
shroud, then there is a cap to retain the shroud in the groove. The plug and
cap were connected using two stainless screws. Guess what? The corrosion
was so bad I had to hacksaw stuff to get them apart.

Use zinc-chromate paste to prevent galvanic corrosion.
Here in the Netherlands it goes by names like "Duralac", "TefGel" or
"WeiCon". Every decent rigger is familiar with it.

Luck, Len.

engsol wrote:
The mast is on sawhorses. I inspected the spreaders. I liked what I saw.
Aluminum tubes going from round at the shroud end to oval at the mast, with
really sturdy mounts.

Here's the problem. The shroud end has an aluminum plug with a groove to accept the
shroud, then there is a cap to retain the shroud in the groove. The plug and
cap were connected using two stainless screws. Guess what? The corrosion
was so bad I had to hacksaw stuff to get them apart.

I'm having the machine shop make new plugs and caps, but I'm at a loss
as to how to secure the cap to the plug, to say nothing about how to secure
the plug into the spreader tube....without getting them chewed up again.
Bronze screws, if I can find them?

Any hints? Nigel Calder, you read this newsgroup? lol

Thanks,
Norm B
Everyone else has mentioned Duralac etc. and something like that will
still be essential on all mating surfaces and threads, but if the cap is
retained by stainless screws into tapped aluminium holes GET THE HOLES
HEILICOILED. Then you have steel on steel which is a *much* better
state of affairs. DO NOT UNDER *ANY* CIRCUMSTANCES USE ANY COPPER, BRASS
OR BRONZE IN CONTACT WITH ALUMINIUM NEAR SALT WATER OR SPRAY. (the only
quicker way of making aluminium look like swiss cheeze is mercuary or
electrolysis due to a faulty DC or shorepower system)

As top the plug into the spreader tube, either through bolt with fibre
washers under the nut and bolt head and plenty of Duralac (ideally
sleeve the bolt with some thin tough heatshrink sleeving to totally
avoid stainless to aluminium contact on the thinner aluminium of the
spreader tubeing) or epoxy it in or possibly rivit it with an aluminium
rivit (not a pop rivit)

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:
'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed,
All varnished hot moulded wooden racing dinghy.