>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 |
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