From: ajb8886@ritvax.isc.rit.edu
Subject: Re: electronic rustproofing.
Reply-To: ajb8886@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology
Date: Mon, 12 Oct 1992 00:25:42 GMT

In article <70692@hydra.gatech.EDU>, gt8166a@prism.gatech.EDU (DOERSCHUK,DAVID OAKES) writes:
>In article <2927645605.1.p00140@psilink.com> p00140@psilink.com (Gary A. Woodward) writes:
>>What a tremendous resource this is!  Does anyone have any experience 
>>with electronic rustproofing device for cars.  The supplier says (naturally)
>>that it is currently used on bridges and heavy equipment in salt mines.  
>>Is this product based on a sound foundation of research.  Or is it just 
>>something else to sell the public?  Could it hurt my on board computer 
>>in car?  
>
>The railroads have used them ("sacrificials") for years, they seem to
>work good, and are certainly based in valid chemistry.  They're often
>just blocks of magnesium electrically connected to the car's body and
>frame.  Instead of forming ferric oxide (rust) on the car's body,
>you get magnesium oxide on the block of magnesium.  Eventually, the
>magnesium has all turned to magnesium oxide, and you just replace it;
>hence "sacrificial".  The main caveat is that you've GOT to have a
>good electrical connection throughout the car's body panels and frame.
>Next time you walk along a railroad track, look at the "joints" between
>two pieces of track.  Notice that there's a big ground strap connecting
>the two adjacent rails.  This is, in part, to keep all the track at the
>same potential for safety reasons, but its also so that the track will
>all be protected by the sacrificial.  I don't know the spacing of sacrificials
>on the track (e.g. one block per mile?) or what the modern sacrificial is
>made of (used to be magnesium), but the idea is that you've got to have
>a high quality electrical connection between all parts of the car's body
>and frame.
>
>I can't think of any reason why using a sacrificial would cause any
>problem with your car's computer.
>
>You didn't mention how much they wanted for it, but if its more than 
>about $40, I'd just go buy my own magnesium block and hook it up.  The
>installation is moderately time intensive, since you really ought to make
>sure (by testing) that all your body panels have a good quality electrical
>connection to the point where you're attaching the block.
>
>Probably the easiest place to find out more would be an intro chemistry
>text.  I was trying to think of a railroading book that would have 
>something about this, but I can't think of one.  
>
>It isn't snake oil, it actually works.  Neat, huh?!
>
>Good luck, and if you pursue it, let us all know what you find out.
>
>Dave Doerschuk
>
>-- 
>Dave Doerschuk
>Georgia Institute of Technology, Atlanta Georgia, 30332
>uucp:	  ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!gt8166a
>Internet: gt8166a@prism.gatech.edu


The technique described has been used on virtually all ocean going craft for
quite some time.  Most metal-hulled boats have it, and quite a lot of
fiberglass pleasure boats as well (before you flame me, it's to protect the
metal drive mounts and prop from rust, not the fiberglass :).

It's very effective, at least when you're dealing with a lot of salt water.

Alex



From: Steve.Kaess@f417.n109.z1.fidonet.org (Steve Kaess)
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