Date:         Wed, 23 Sep 1998 23:21:57 -0400
Reply-To:     John Anderson <janderson@IOLINC.NET>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
From:         John Anderson <janderson@IOLINC.NET>
Subject:      Re: head electrolysis cure?
Comments: To: vanagon@vanagon.com
Content-Type: text/plain; charset="iso-8859-1"

>Mark,
>
>  A sacrificial anode needs to be a block of metal electrically connected
>to the metal you are trying to protect. So I do not think metal disolved
>in the coolant would do what you want. The anode will end up as a disolved
>salt in the coolant when it is corroded instead of the metal you are
protecting.


This may actually work and in point of fact nearly all Wasserboxers come
with such a thing, we typically call it the transmission case.  A close
inspection thereof on earlier vans in salt climates will show that it is
rapidly dissapearing protecting the aluminum engine case.  Terrifyingly
dissapearing in some instances, the Mg alloy being more reactive than the
aluminum apparently.  I've proposed these and other methods over the years
but decry any form of electrolytic protection to any real extent as the
problem seems electrochemical and physical in nature.  Certainly corrosion
is always due to difference in potential, but on most vans, that difference
isn't a lot.  But another clue struck me the other day as I sandblasted the
upper coolant tube for a 1.9,  these steel tubes rust like mad in these
climes, can rust out every 4-5 years!!!  Take a look at what they do, they
connect manifold runner to manifold runner and thereby via the intake bolts,
head to head for another current path.  Interesting.  I personally always
daisy chain a heavy braided ground from chassis to head to block to head,
particularly on 1.9's who IMNSHO usually suffer major FI maladies from the
stock ground strap disintegrating and the ground return for the engine
passing through the myriad of FI grounds on the drivers side head.  It is
usually necessary to cut several inches off those grounds, crimp on new
connectors, and solder them to insure proper smooth running on a 1.9 in the
rust belt at these ages.  Some of the wires may need full replacement if
they have carried too much current and become to embrittled (O2?)  Anyway I
do these things but still don't think they are worth a damn as the physical
problems will still initiate corrosion, but hell it doesn't hurt, and a
couple chunks of Mg on the heads wouldn't either.  FWIW VW did start placing
sacrificial annodes on the body to fender joints in the mid 80's.  Most
underground utilities use Mg annodes as corrosion prevention on underground
steel lines, and an old EE friend of dads used to swear by bolting pieces to
the frame of his car in numerous locations and replacing them when they
dissapeared.  He had a '71 Chevy pickup in far better condition than its age
and mileage warranted.  TIFWIW.

John
janderson@iolinc.net