On Wed, 27 May 2015 06:38:35 +0700, Bruce in Bangkok wrote:



I am in the process of building a permanent mooring and have a heavy
galvanized anchor as well as several lengths of galvanized and
stainless. However I have heard stories about rapid galvanic corrosion
when connecting stainless and galvanized together under water.

My question is, can I (should I) connect the heavy length of stainless
chain to a lighter length of galvanized chain and to the galvanized
anchor using stainless shackles and swivels? Or with galvanized
fittings?

I would normally plan on inspecting the mooring on a annual basis.

The reasoning in mixing materials is basically that I've got the two
lengths of chain and if useable need only to buy the shackles and
swivel.

Anyone with personal experience or specific knowledge of joining
stainless and galvanized in seawater?


I do. The galvanized layer lasts about a season and then
you have rusty chain which slowly becomes thinner and
thinner so you end up replacing the chain every three or
so years. Go stainless steel all the way. I would recommend
3/8", or even 1/4" for a large boat, stainless steel chain
which can cost you like 20-30 bucks a foot but it's worth
it over the long haul as it seems to lasts indefinitely
and can be reused should you decide to abandon the
mooring. Be sure to safety wire (SS) all the shackles as
SS tends to be slippery enough to unscrew all by itself.

Galvanized swivels tend to rust up so they stop swiveling.
Again, use stainless steel everywhere. I even use stainless
steel thimbles on the mooring lines. I use twins.

As for the anchors, and I say anchors because you should
use more than one, they can be galvanized as they will
end up as rusty hulks after several years. For my mooring,
which is an all-weather (including hurricanes)mooring,
I used two 350-pound, 48" diameter, manhole cover rings.
Not the covers themselves but the cast iron housing
the covers fit into. It's easy to shackle a loop of SS
chain around them.



--
Sir Gregory