My inorganic chemistry is rusty (no pun intended), but I think that the
RadCap is valid electrochemically.

The radiator and engine block are connected electrically (since they are
all somehow connected to ground), so that's not a problem.

The reduction potential for Al -> Al3+ is +1.66 volts, and the
"reduction" potential for Mg -> Mg2+ is +2.37 volts, so the magnesium
should be preferentially oxidized, thus saving the aluminum from
dissolving.

The biggest problem with a Vanagon is that I'm not sure how you keep the
magnesium constantly in contact with the coolant solution AND grounded to
the radiator/engine; there's no radiator cap, right?

I'm pretty sure that my chemistry is correct here, but if someone notices
a mistake, please let us all know.

Marty Wallace, Chemistry-Type (1984 Westfalia)
Chico, California

> Date:    Tue, 29 Sep 1998 15:04:57 -0700
> From:    "Richard M. Myers" <myersr@SPAWAR.NAVY.MIL>
> Subject: Re: [Fwd: head electrolysis cure?]  Re: [Fwd: head
electrolysis cure?]
>          Re: [Fwd: head electrolysis cure?]
 Hello Ari,
> Better than on the radiator would be to connect a magnesium or other
> cathode-protection chunk electrically to the engine block somwhere
> immersed
> in coolant.  Unless what you're trying to protect is the radiator......
> Any ideas on where this can be done without major disassembly?  Also,
> are
> there any chemist-types who know *for sure* which  sacrificial metal
> will
> provide the protection desired for this application?
> I may be short some of the details, but tinkerers on this list can
> probably
> figure out a better solution than the 'radcap' as described.
 Tom
> ===============================
> >Reply-To: Ari Ollikainen <Ari@OLTECO.COM>
> >Sender: Vanagon Mailing List <Vanagon@VANAGON.COM>
> >From: Ari Ollikainen <Ari@OLTECO.COM>
> >Subject:      Re: head electrolysis cure?
> >Comments: To: Vanagon@VANAGON.COM
> >To: Vanagon@VANAGON.COM
> >
> >>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.
> >
> >        It's interesting that this thread would surface at this time...
>
> >        While watching a NASCAR event last Sunday, I didn't pay much
> >        attention to the commercial for a new product called "Rad Cap"
> >        which purports to provide *exactly* this sort of protection.
> >        Unfortunately its form factor (normal radiator cap) is wrong
> for
> >        the Vanagon cooling system :-(
> >
> >        Later I saw it again in the MotorTrend October 98 issue "Car
> Care"
> >        section...see http://www.motortrend.com/oct98/cc/cc_f.html
> >
> >        A "RAD" SOLUTION TO ALUMINUM EROSION
> >
> >        The Rad Cap offers an innovative approach to minimizing the
> type of
> >        internal metallic erosion caused by electrolysis: the stripping
> of
> >        ions from system metals due to stored electricity in the
> cooling
> >        system. Based on a concept used in marine applications, the Rad
> Cap
> >        contains a sacrificial magnesium anode that hangs from the
> underside
> >        of the cap and is immersed in the coolant. The idea is that
> magnesium
> >        is a more active metal than aluminum, so it will dissolve
> before
> >        aluminum, saving wear on the engine's aluminum parts. According
> to the
> >        company, proof that it works is evident from the fact that the
> >        electrical voltage in the solution is usually much higher
> around the
> >        anode than elsewhere in the coolant. The Rad Cap costs about
> $20, and
> >        its effective lifespan is estimated at 18-36 months.
> >        Contact DD&E, 925/689-6214.
> >
> >
> >
> >      OLTECO                    Ari Ollikainen
> >      P.O. BOX 3688             Networking Technology and Architecture
> >      Stanford, CA              Ari@OLTECO.com
> >      94309-3688                415.517.3519
>
>
> +------------------------------------+
> |  CycoActive Products              tel (206) 323-2349
> |  701 34th Ave             fax (206) 325-6016
> |  Seattle, WA 98122    USA
> |  webpage:   http://www.cycoactive.com
> |  e-mail:  TomMyers@cycoactive.com
> +------------------------------------+

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