Entirely true, and they both cause similar damage. We are very familure with
galvanic corrosion in the brine waters of the St. Johns. You can actually
measure the electrical production with a sensitive multimeter. Electrolysis
is a symptom of galvanic corrosion. It degrades the anode metal.

The anode installation and wire bonding fix will take care of both, keeping
your boat pretty.


An interesting experiment.
in a plastic bucket, make some salty water.

place a piece of aluminum foil on one side of the bucket. (top out of
water.)

Place a piece of stainless steel on the other side.(top out of water.)

Set a multimeter to its most sensitive (millivolts) setting and dip one
probe in the center of the bucket. Touch the other probe to the stainless.
record results.

move Aluminum closer to stainless and repeat measurements. record results.

attach a piece of immersed copper wire to aluminum. Allow to stand for 1
day.

Observe stainless steel.

Next

discard salt soulution and rinse container.
place aluminum foil in bottom of bucket.
Mix HOT water with 2 tablespoons of baking soda.
place badly tarnished sterling silver spoon (or other item) so it does not
contact the foil, and measure millivolts from item to water. record results

next make contact with the foil while observing meter. It should spike
sharply and the tarnish jump from the silver to the foil.




--
Capt. Frank

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"Joe Blizzard" wrote in message
...
"Capt Frank Hopkins" wrote
Electrolysis, otherwise known as galvanic corrosion

Begging leave to differ, Capt Frank, but they're two different things.
What
you're describing is galvanic action caused when dissimilar metals
immersed
in an electrolyte decide to act like a battery and generate electric
current
all by themselves. Electrolysis happens when an external source of
electrical current, like your starting battery or shore power supply,
generates electrical current through the water.

My outboard has an anode built into the lower unit and it looks fine, is this
enough or should I add one to be safe?

You are ok with an anode on the motor, but be sure to add at least 1 to the
hull. 2 would be better. Make sure they are the correct type for freshwater.
Since you keep the boat on a trailer, and use it only in freshwater, I don't
think either electrolysis or galvanic corrosion will be a major factor in
your boat's lifespan. A couple of good coats of wax each season will be more
benefit.

I would electrically bond everything, especially energy using devices'
(lights, radios, fishfinders, ect.) mountings with a separate copper
"ground" wire terminating at the (-) pole of the battery(s). This will give
your devices their best performance and eliminate hot spots in the hull.

Replace freshwater anodes every 24 - 36 months even if they "look ok".

--
Capt. Frank

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__\_| oooo \_____
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"CCred68046" wrote in message
...
My outboard has an anode built into the lower unit and it looks fine, is
this
enough or should I add one to be safe?

Thanks Capt Frank...

This is an 18' all welded boat, cant wax it, it has a rough finish kind of
paint on it. Everything is grounded but I could add a few hull anodes to be
safe. How do hull anodes mount? And where do youI put them for the best
protection?

If its the type of paint I think it is, anodes may be unnecessary on the
hull. I would have to see a picture.
--
Capt. Frank

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__\_| oooo \_____
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"CCred68046" wrote in message
...
Thanks Capt Frank...

This is an 18' all welded boat, cant wax it, it has a rough finish kind
of
paint on it. Everything is grounded but I could add a few hull anodes
to be
safe. How do hull anodes mount? And where do youI put them for the best
protection?

Its like the paint they use on a camo duck boat only one color. Not glossy.
Heavy duty boat, thick aluminum.

On 18 Feb 2004 15:46:28 GMT, obull (CCred68046)
wrote:

Its like the paint they use on a camo duck boat only one color. Not glossy.
Heavy duty boat, thick aluminum.

================

If you use the boat in fresh water and store on a trailer, you really
have no reason to worry about electrolysis. Just ensure that your
batteries are turned off when you leave the boat and keep the bilge
dry.
..

"CCred68046" wrote in message
...
Thanks Capt Frank...

This is an 18' all welded boat, cant wax it, it has a rough finish kind of
paint on it. Everything is grounded but I could add a few hull anodes to
be
safe. How do hull anodes mount? And where do youI put them for the best
protection?


I have a heavy aluminum boat also. There is an extension of the bottom at
the transom. About 1.5" Allows some tuning of the trim via bending. Mine
has a zinc screwed to the boat on each side on the lip. I can send you an
email pic if you want.
Bill

Mine
has a zinc screwed to the boat on each side on the lip. I can send you an
email pic if you want.

OK thats cool, I think I know what you mean but mine does not have anthing like
that and I avoid putting holes in it.

"CCred68046" wrote in message
...
I was reading a website from a manufacturer of all welded aluminum boats.
There is a warning on the site that says:

"DO NOT GROUND YOUR ELECTRICAL WIRING DIRECTLY TO YOUR BOAT.


The key word here is "directly".

What they are saying is that you should NOT use the hull of the boat for
carrying current (remember that this is about aluminum boats).

On a car, it is standard practice to use the frame of the car as the
return lead to the battery. Thus, the wiring harness carries only the
positive side.

On a fiberglass boat you have no choice but to run "ground" wires to
everything. On an aluminum boat, you might consider using the hull of the
boat as a conductor, but it could lead to problems. To start with, aluminum
is not that great of a conductor. Second, every connection is likely to
have a copper to aluminum bond, which puts to dissimilar metals in contact.
Two dissimilar metals plus electrical current can do bad things. Third,
every joint in the hull could suffer from electrolysis.

Note that this is a separate discussion from the electrolysis to the water
problem. There will be those that argue that the hull should be completely
isolated from any electrical source, but that is not an easy thing to
accomplish.

Rod McInnis