I was putting a new engine in my bosses '69 Ford truck and while removing the rad I noticed how clean the inside was.  I asked my boss if he had replaced it recently and he said it was the original and he attributed it to using distilled water.  The distilled water does not have the ions from salt to support electrolysis (corrosion).  Just because water comes in contact with a metal does not mean there is metal ions instantly in that water.

John

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