Date:         Wed, 8 Aug 2001 10:35:07 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Electronic Rust Protection?
Comments: To: Terry Kay <CTONLINE@WEBTV.NET>
In-Reply-To:  <17809-3B714181-17@storefull-132.iap.bryant.webtv.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

It ain't *quite* that simple, Terry --
At 09:41 AM 8/8/2001, Terry Kay wrote:

>But an electrical imbalance that causes rust?

Absolutely.  Rusting is an electrochemical reaction (or rather set of
reactions, see
<http://antoine.fsu.umd.edu/chem/senese/101/redox/faq/how-iron-rusts.shtml>
for some pathways.  But the fundamental process underlying rust formation
is that the iron loses electrons.  In fact the current definitions of
oxidation boil down to "losing electrons."

One method of corrosion control involves supplying excess electrons which
use up the reactive elements before they can strip electrons from the
iron.  This can be done by using electrodes such as magnesium or zinc which
provide electrons by sacrificing themselves, or by actively impressing an
electric current on the system.  Both methods are extensively used on
ships, pipelines, buried tanks etc.

HOWEVER...the snag is this whole system works *within the fluid where the
corrosion is taking place."  If you have a ship in salt water, or a
pipeline buried in conductive earth, this is quite practical.  But on a
land-based system where the corrosion is taking place in tiny isolated
places, it becomes a practical impossibility to get the current to where
you need it.  You have to have a continuous conducting medium to complete
the circuit.

So on the face of it, automobiles are not a good candidate for
impressed-current cathodic protection, unless you're burying them or
dropping them in the sea.  The wiggle room, if any (and I haven't yet seen
absolute proof one way or the other, though the anticorrosion professionals
tend to fall down laughing when the subject is mentioned) is whether salt
splash etc. can provide a sufficiently continuous electrolyte medium for
this method to have any effect.



>I don't think so.
>
>Then I want to know where my "cathode", and "anode" portion of my
>vehicle is located, so I can tend to them immediately.

Every tiny speck of rust has one (or many) cathodes and anodes.  Fix the
rust and you'll have tended your a's and c's...

david

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"