Chris wrote:
> I had my cylinder head refurbished four years ago. Last October one of
> the valve seats gave way. When I took it off the car. there was
> evidence of severe corrosion and the guy at the local head shop told
> me it appears to be electrolysis. Does anyone know what causes this?
What he meant was galvanic corrosion. This happens when materials of
differing galvanic potential are assembled together. Steels and
aluminum have around 0.5 V difference which is enough to give you
some corrosion under the right conditions. This galvanic cell
between the two materials generates a flow of electrons and in the
process oxidizes the material. It needs moisture generally to
accelerate this corrosion. My alpine engine was completely dead
after sitting for ten years due to a galvanic couple between the
pistons and the cylinder walls. Unfortunate fact of life but this
also illustrates the need to use antifreeze in motors with aluminum
heads and cast iron blocks since this fluid has galvanic inhibitors.
For what its worth.
Kind regards,
JIm Cantrell
76 XJ12C
76 XJ6C
66 Alpine 2.8L
>
> Chris Stephenson
> Alpine III
> Atlanta, GA
>
>
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