Date:         Tue, 22 Sep 1998 17:17:43 -0700
Reply-To:     Malcolm Holser <mholser@ADOBE.COM>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
From:         Malcolm Holser <mholser@ADOBE.COM>
Subject:      Re: head electrolysis cure?
Comments: To: Mark Gajewski <mgajewski@MANVILLERUBBER.COM>, Vanagon@VANAGON.COM
In-Reply-To:  <3607ED46.2037E1EC@manvillerubber.com>
Content-Type: text/plain; charset="us-ascii"

Aluminum would protect the Zinc, not the other way 'round.  Not too many
things
that worse than aluminum this way.

Ships use zinc.  Aluminum forms a rather impermeable oxide layer, and so pure
aluminum does not do badly -- it immediately "rusts" but basically protects
itself.
Aluminum *alloys* really suck in this regard.  Typically, there are
crystals of
other materials that keep the covering from being complete, and the
aluminum is
very vulnerable.  Airplanes are made from aluminum alloys that are clad
with pure
aluminum, so that only the pure stuff is exposed.  They call this stuff
"Alclad".
Aluminum can be "anodized" to build up a relly good layer.  It might be
interesting
if anodizing the heads would help anything -- maybe the "hard black"
anodizing.

Malcolm

>Perhaps some dissolved zinc in our coolant would work, being preferred
>in the red/ox reaction to the aluminum of our heads?  Any chemists or
>metallurgists out there who could comment on this?  I am not certain of
>all the details but I believe the concept is correct...although if it is
>wouldn't VW have simply added this "anode" material to the Autobahn
>coolant to prevent/eliminate the leakage issue and all the irate
>wasserleaker owners...have changes been made to the coolant since the
>leakage problem arose?  I suppose that would make regular coolant
>changes absolutely mandatory to insure that the "anode" material has not
>been completed consumed by the reaction.
>Mark
>