You probably should be using magnesium anodes in freshwater.

Magnesium is less reactive than zinc; you are interconnected to ALL
OTHER BOATS in your marina since you (not such a good idea) keep the
AC connection at all times when you're in your slip. The problem will
be that if you are essentially bonded (via the AC ground) to another
boat(s) that does have magnesium, YOUR zinc will be the one that is
consumed since it is the least noble.
Consider to install a 'galvanic isolator' so that your boat is
'isolated' from that common AC ground wire !!!!!!!!!! ...... then get
a calibrated electrolysis cell (corrosion reference cell) and be sure
that you have the exact AMOUNT of anode needed for ***your specific
location*** for the best or most effective protection ........
http://www.boatzincs.com/corrosion-r...electrode.html. .... a
lot of good info is found on the www.boatzinc.com website.

Rich,
Please quit giving advise about things you do not understand. I am being
polite. You are misinformed. Please do your homework. There have many
discussions about this in the recent past.
Steve

"RichH" wrote in message
...
You probably should be using magnesium anodes in freshwater.

Magnesium is less reactive than zinc; you are interconnected to ALL
OTHER BOATS in your marina since you (not such a good idea) keep the
AC connection at all times when you're in your slip. The problem will
be that if you are essentially bonded (via the AC ground) to another
boat(s) that does have magnesium, YOUR zinc will be the one that is
consumed since it is the least noble.
Consider to install a 'galvanic isolator' so that your boat is
'isolated' from that common AC ground wire !!!!!!!!!! ...... then get
a calibrated electrolysis cell (corrosion reference cell) and be sure
that you have the exact AMOUNT of anode needed for ***your specific
location*** for the best or most effective protection ........
http://www.boatzincs.com/corrosion-r...electrode.html. .... a
lot of good info is found on the www.boatzinc.com website.

"RichH" wrote
you are interconnected to ALL
OTHER BOATS in your marina

No, I'm not.
I have a private dock on the same river as the OP.
He's the one in a slip.
And I believe you have your galvanic series backwards. Magnesium is more
anodic (less noble) than zinc, which is why it's typically recommended for
fresh water. The water being less conductive, a larger electrode potential
is desirable if you want to achieve similar protection.
When I had my powerboat in the Kanawha and was using zinc anodes, they'd
develop an insulating layer on their surface after a couple of weeks, taking
them out of circuit. Abrading them down to shiny metal would restore their
effectiveness, but it was a PITA, so I switched to magnesium. This reduced
the problem, but didn't totally eliminate it, and I still never saw
significant loss of material from my anodes, which is why I suggested to the
OP that he might have power issues.

On Wed, 20 Aug 2008 09:21:42 -0700 (PDT), RichH
wrote:

Magnesium is less reactive than zinc;

They used magnesium in incendary bombs because it will burn easily.
But it's less reactive? What zinc is, is cheaper. Aluminum is the
standard fuel in firecrackers, and my boat is aluminum. Spirit Lake in
Iowa has a number of aluminum boats originally bought by the no longer
there boat rentals of fifty years ago. The businesses are long gone
but the boats remain. None have ever seen a zinc or anything like it
unless it was perhaps built into an outboard moter. None of these
boats have shore power, most have no battery. No bronze thru hull
fittings. No corrosion in any of these boats in fifty years. Active or
not, bare aluminum boats don't seem to corrode even in sea water, at
least not withour help from dissimilar metals or shore power. We have
a magnesium ladder that has been out in the weather, hung for storage
on the outside of a shed, for fifty years. It got darker, is the only
sign of weathering.

Casady

Opppps, Brain Fart !!!

Zinc (-1.0v) less reactive than Mg (-1.6v).

Still the rest applies: galvalnic isolator, common bonding through the
AC ground, reference cell, etc., etc.

Rich,
No, it does not. The problem in your neighbor's boat affecting your boat IS
the common bonding. Without that, there is no circuit! Secondly, a ground
isolator is not a cure, it is an inhibitor because the leakage current
through that diode is still very damaging. These measures only address stray
current corrosion. Galvanic corrosion on the other hand, causes identical
damage, but is caused by dissimilar metals in a common electrolyte and
sacrificial anodes are another band aid, not a cure. These anodes can
actually encourage galvanic corrosion. This is a very complex subject and if
you are suffering from this, the goal should be elimination, not a band aid.
On another point, there is a lot of advise out there in print that is either
incomplete or unadulterated b-ll s---t and propagating it without a thorough
understanding does no one any good.
Steve

"RichH" wrote in message
...
Opppps, Brain Fart !!!

Zinc (-1.0v) less reactive than Mg (-1.6v).

Still the rest applies: galvalnic isolator, common bonding through the
AC ground, reference cell, etc., etc.

On Aug 21, 12:19*am, "Steve Lusardi" wrote:
Rich,
No, it does not. The problem in your neighbor's boat affecting your boat IS
the common bonding. Without that, there is no circuit! Secondly, a ground
isolator is not a cure, it is an inhibitor because the leakage current
through that diode is still very damaging. These measures only address stray
current corrosion. Galvanic corrosion on the other hand, causes identical
damage, but is caused by dissimilar metals in a common electrolyte and
sacrificial anodes are another band aid, not a cure. These anodes can
actually encourage galvanic corrosion. This is a very complex subject and if
you are suffering from this, the goal should be elimination, not a band aid.
On another point, there is a lot of advise out there in print that is either
incomplete or unadulterated b-ll s---t and propagating it without a thorough
understanding does no one any good.
Steve

"RichH" wrote in message

...



Opppps, Brain Fart !!!

Zinc (-1.0v) less reactive than Mg (-1.6v).

Still the rest applies: galvalnic isolator, common bonding through the
AC ground, reference cell, etc., etc.- Hide quoted text -

- Show quoted text -

OK ...

I've read thru the posts, and now I'm MORE confused than ever. A bit
of background; my previous vessel had been stored in the very same
lake we visit from time to time (Summersville, WVa). When I plopped
it into the Kanawha River, it seemed the zincs didn't really do a
great deal, more the lower end of the outdrive took the hit. So now I
have this brand new vessel (2007 260DA) .. don't know if the "zincs"
are Zinc or Magnesium .. I'm guessing Zinc, but you know what guessing
does.

I've cleaned the gunk off 'em with a small steel brush, down to the
shiny. I expect I'll replace 'em when I pull the vessel out of the
water for winterizing, but that still doesn't answer the questions in
my mind. 1) I have Sea Ray's Galvonic Isolator (standard install) ..
2) if I have troubles with shore power in my slip, what's next? I
can't very well leave the vessel unplugged, can't very well dictate
the wiring practices used by the marina.

What's next? And thanks!

~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=

john burton
Bach 50B3 Bass Trombone
Kanawha Valley Community Band / Slide-by-Slide
South Charleston, West Virginia

On Aug 20, 10:50*pm, RichH wrote:
Opppps, Brain Fart !!!

Zinc (-1.0v) less reactive than Mg (-1.6v).

Still the rest applies: galvanic isolator, common bonding through the
AC ground, reference cell, etc., etc.

, while you are plugged in to shore you are only using a very small
amount of current; just say, a few watts an ISOLATING transformer
might be the answer?
The transformer might not handle anything really heavy but a small
trickle charger to keep up the battery only takes a few a watts on the
AC side. For example 12 volts at say 3 amps = 36 watts. That's no
more than some laptops, or a model train set!

However to run a fridge all the time might require 360 watts. That's
still not that impossible except that the transformer must be bigger/
heavier. And it must be able to handle the starting loads of a fridge
compressor.

An Isolation transformer has completely separate input and output
windings. So that it prevents the flow of electricity from even the
'ground' system on shore, which is also most likely, connected to
other boats etc.; through the metal parts of your boat into the
water. Even so called freshwater is slightly conductive.

Also if you have two dissimilar metals on your boat which are
connected together electrically both being in the water you have an
electrolytic cell. See note. Current will flow, even so slightly and
the less noble metal will slowly corrode.

Some early batteries, now called 'Alkaline cells' were invented by
LeClanche. They consisted of a glass jar with a weak alkaline solution
of water and sal ammoniac. The positive electrode was usually a carbon
rod which did not suffer any erosion. The negative (and less noble)
electrode was zinc and if was consumed and eaten away. Back then
people could go to a hardware store and buy new zinc (which was
sometimes used for roof flashings anyway) and the stuff to mix with
water to make the alkaline electrolyte. A similarity to two metals on
a boat.

There are two likely conditions.
1) Leakage through boat into the water and/or other boats with their
leakage into the water going to ground through YOUR boat.
2) Electrolytic corrosion on YOUR boat regardless of whether it is l
plugged in to shore. So for example a zinc (or magnesium) clamped and
in metallic contact to say an outboard is designed to be eaten away,
thus protecting the metal outboard motor from being eroded.