De-ionized water [duplicate]








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[Is pure water very corrosive?](/questions/7467/is-pure-water-very-corrosive)

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Closed 8 years ago.



Is de-ionized water more corrosive to metals than tap water? I have read that it "wants" the removed ions back and will aggressively take them from any available source.




The Wikipedia article merely states that *sole consumption of purified water may deplete some electrolytes through normal excretion and lack of replacement*, not that it somehow "wants" the minerals.


As a matter of fact, pure, deionized water is much **less** corrosive to metals and is often used in closed systems to **prevent** corrosion because it helps prevent [galvanic (electrolytic) corrosion](http://en.wikipedia.org/wiki/Galvanic_corrosion). 


Automotive coolant antifreeze contains specific corrosion inhibitors safe for aluminum and iron parts, but if water needs to be added, it should be distilled water, to prevent galvanic corrosion.


People living in northern climates often encounter corrosion of vehicles due to road salt, and learn to wash vehicles with tap water to remove the salt (high-purity or distilled water would be better, but not cost effective).


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