Adam:
I am not familiar with this particular product, but it is
possible to use
a remote anode along with an impressed voltage to control corrosion.
Galvanized metal does this same thing passively, but requires
that the
zinc be distributed over the metal to be protected. This is done to
provide corrosion
protection in 2 ways:
1. The direct galvanic action (i.e. Steel and Zinc form a
battery cell) that
causes the zinc to corrode preferentially (or 'sacrificially) leaving
the underlying
steel intact.
2. The chemical properties of zinc are such that any pinholes in
the zinc
film are filled in by the zinc through electrochemical action, thus
sealing off
the steel from the corrosive environment.
With non-passive cathodic protection, an external power supply
is required.
The same principal of a "sacrificial" metal applies, but there is no
protective
film over the steel. The corrosion protection only works as long as a
voltage is
applied, the circuit is intact, and there is sufficient metal available
at the
anode to sacrifice itself.
You can use another metal for the sacrificial anode that might
not form
a battery when used with steel, since the electric current is supplied
from an
external battery. You might, for instance, want to substitute a metal
that is
cheaper than zinc as the anode, or perhaps a metal that would provide
protection, but corrodes more slowly, reducing the frequency of anode
replacements.
Another advantage is that the sacrificial material can be
segregated to a single
or a few locations, so it can be added long after the basic steel
structure has been
built.
The disadvantage to the non-passive system is the additional
complexity, the
higher cost, and that any steel that is insulated from the electrical
circuit
(with rubber washers, for example) is NOT protected. If the current is
interrupted, the protection disappears. You also need to periodically
replace the
anode, depending on how rapidly it corrodes.
Nuclear submarines use the passive system, by bolting zinc
"ingots" to the
inside of the outer hull. Then once a year they remove whatever is left,
and bolt on
a new ingot. Many ships use a similar system.
As to whether or not this particular product is effective, I
can't say. But
the principals are sound and widely known.
Cheers,
Vance
------------------------------
Cogito Ergo Zoom
(I think, therefore I go fast)
TR6 Web page: http://home.comcast.net/~v.navarrette/
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Adam C Beasley
Sent: January 21, 2005 12:54 PM
To: 6pack@autox.team.net; 'Triumph'
Subject: Electro-shield
Has anyone ever tried the "electro-shield" rust preventative product?
Supposedly it prevents corrosion by supplying electrons to the metal.
Does it work or is it another gimmick?
Thanks!
Adam
73 TR6
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