Re: galvanic reaction

["Jim" <alarminex@xxxxxxx>]

mikey wrote:
> Greenish hue, sometimes rust like color, whitish on boards. I've seen
it,
> especially on stuff what got wet. Where's Jim? He works on boats,
> fascinating what he goes through to protect shit.
>

On boats there's always some kind of galvanic action going on
somewhere.

For those who are not boaters, (especially in salt water), if you want
to have any propellers, rudders, or any metal that is in contact with
the water, left on your boat, you'd better make sure all metal object
that are in contact with the water, are bonded ( attached with a heavy
wire where they protrude inside the boat) to each other and that you
have sacraficial zinc's attached to the underwater metal objects. These
pieces of zinc are made of a compound that will erode quicker than the
bronze, brass, or stainless steel that they are attached to. It's also
important to check them during the season because if they should erode
faster than normal, it's likely due to an electrical problem with
either your boat, another nearby boat in the marina or with the
electrical service on the dock. There are always the horror stories
about people who havent checked and have had portions of their engines
errode away. There are even zinc rods that have to be inserted into the
cooling system flow, since much of it is isolated from the
(grounded/bonded) engine block by waterjacket gaskets but is still in
touch with the water.

As far as electronics goes, I've never seen it on my boat, since I seal
everything that is worth protecting, and remove all electronics during
winter layup. Marine electronic products are sealed and boards are
sprayed with sealer. But on other boats, where owners are not so
protective, sometimes an electronic device can be affected by this
white (corrosive(?) powder. Items such as TV's and devices not
especially made for marine use, have a reduced life expectancy.

Generally un-anodized aluminum does "powder up" ie. corrode in a salt
atmosphere. I've also seen "white  powder" on electronic components but
I assumed it was just due to the residual salt in the atmosphere
reacting with components in the metal leads and possibly causing some
electrolysis. I've thought that most of the electronics, being low
voltage/current, would therefore cause a small amount of electrolysis
due to the salt air.

I don't know if there's a connection between the aluminum white powder
and this white powder, or not. Perhaps due to the solder on the
leads.(?) When salt water gets on electronics, there's the typical
green corrosion, which I assumed was from any copper present and
there's usually a white powder, which I assumed to be some combination
of water, salt/elements in the water, reacting to the presence of
electricity and other dissimilar metals ie. electrolysis of a different
sort.

I've never seen a resistor lead corrode on a land side site without
some sort of catalyst or outside influence. It occurs to me that heat
caused by a to small a wattage resistor, in a moist/humid atmosphere,
might cause corrosion to occur at the lead/resistor juctions. Also, are
all resistors of equal quality? I'd imagine that there are some really
cheap resistors out there that are made out of compressed mud and
bamboo. Could be bamboo sap you're seeing.