At 12:03 PM 6/5/96 EDT, you wrote:
>You and that guy at Road & Track! While cavitation can be destructive, don't
>discount the electrolysis in the cooling system resulting from the copper in
>the radiator attacking the aluminum in the pump housing (and the water
>contact areas of your intake manifold (think about those pits - there isn't
>much cavitation there). The whitish sloppy stuff in the cooling system is
>most likely Alumina (the product we make here) which is Al2O3 and may be
>hydrated with one to three molecules of H2O chemically bound - that's how
>most "producible" Aluminum is found in nature. Copper and Aluminum are
>bitter enemies - ask any electrician - just putting them next to each other
>accelerates the corrosion - bathing them in a common electrolyte solution
>actually creates a simple battery. In this case, I believe that the chemistry
>is at least as big a factor as the cavitation.
Tom,
The pitting area I was discussing was the area just adjacent to the water
pump. After you get to the interface between the front cover and the block
and the heads and the intake manifold, the electrolytic corrosion takes its
toll. If you examine the degradation in these areas, you will normally find
a grey-green-brown coating on the pitted areas in the water pump area (
cavitation ) and the typical white oxide powder at the iron - aluminum
interfaces. This difference in appearance defines (for me) the process that
is controlling degrdation in the various areas of concern.
Tom Hall
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