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Date:         Wed, 8 May 1996 11:23:42 -0700 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Dwight Mattix<dmattix@qualcomm.com> (Dwight Mattix)
Subject:      RE: Water Pumper Head Corrosion

assuming it is galvanic attack, one needs to know which is the anode. the stud or ...?

in the case of pipes in the ground i recall from explanation by a power engineer i work with that the underground pipe is biased w/ a low voltage (~1Vdc) to make the pipe the cathode. That way it plates up instead of being the sacrificial element and plating out into the earth.

dwight

At 5:55 PM 5/8/96, Maher, Steve (SD-MS) wrote: >>> I propose a ground strap at least, from head to cylinder body, >>>neutralizing any electrical imbalance. If nothing else it seems to me >>>it would cause pitting around elect. connection. >> >>I think this trick works only if the current flows in the right direction. >>Saltwater boats use it to protect their propellors etc. from galvanic >>corrosion (not from chemical saltwater corrosion as I recall). A current >>does inhibit galvanic action... but a current in the wrong direction >>*accelerates* the galvanic corrosion! > >Basic point was, I have a hunch that a simple ground strap from heads >to cylinder, wouldn't help, and might even hurt, by promoting current >flow in the wrong direction. Maybe if you could somehow put a battery >and resistor, in a circuit including the head and cylinder (if those >two are indeed isolated), and so created an electrical potential in the >right direction between head and cylinder, then it might have some positive >effect (no pun intended) (well, not much). > >Any physical chemists out there? They would know far more about the >validity of this effect, if any. Of course, I think my 6-year-old son >also knows more than I about galvanic corrosion sometimes... :-\ > > _______ > /\ o o o\ Steve Maher smaher@gi.com 75461,1717 > /o \ o o o\_______ San Diego, California > < >------> o /| > \ o/ o /_____/o| '80 VW V6anagon > \/______/ |oo| '66 Mustang Coupevertible > | o |o/ '89 Son Sherwin > |_______|/ > http://www.wp.com/IrishMafia > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > The economy's not failing-- there are plenty of jobs available! > I have three of them! > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


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