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.