Darrell,
This seems to be one of those topics that come up perennially, usually in
the spring, along with a wide spectrum of opinions as to whether to use
"deionized", "distilled", soft, etc. water. Over the years, the automotive
industry has developed coolant additives to quite a sophisticated level to
cope with electrochemistry of aluminum/iron/copper systems; but as long as
one keeps within the recommended ranges, the cooling system will stay
corrosion free. Generally, a 50/50 mixture of coolant and
deionized/distilled water is recommended. See for example, this discussion
of commercial diesel engine cooling maintenance:
http://www.finalube.com/fina_check/fina_check_coolant.htm
Over the years I have heard many stories about the dangerous or corrosive
properties of deionized water. The closest I ever personally came to being a
casualty of DI water was when my lab colleague was triple distilling it and
neglected to put boiling stones in the flasks. Luckily, I was upstairs at my
desk when the explosion occurred. We figured it had the explosive equivalent
of about half a stick of dynamite - glass and debris went everywhere. More
recently, in my lab at UCSD, we have very pure DI water on tap. Regular tap
water in San Diego is fairly hard, so I made a habit of using the DI water
in the coffee pot. One of our grad students noticed this one day and was
asked me if I realized that it was going to suck all the minerals out of my
body. I, on the other hand, was (privately) wondering how six years of
college chemistry and engineering had managed to suck all the brains out of
his head. I asked him to provide a rational basis for his assertion, and
none was forthcoming. He did however, upon reflection, relent a bit,
allowing that after the coffee was added to the water it was no longer
deionized and probably not all that bad for me. He's probably also just
another one of the millions of people who pay high prices for one or the
other of the designer mineral waters that are so popular nowadays. If you
happen to live where the water from the tap doesn't taste good - like here
in San Diego - then find a bottled water that tastes good and drink lots of
it. Whatever minerals it has, or doesn't have, isn't going to make any
difference to your health - just your pocketbook.
For some interesting discussion of DI water, check these two Websites:
http://www.finishing.com/110/17.shtml
http://www.finishing.com/147/97.shtml
For a more technical discussion, check this out:
http://www.corrosion-doctors.org/NaturalWaters/corrosivity.htm
"Soft" water is tap water that has gone through an ion exchanger. It
exchanges sodium ions for less soluble ions like calcium and magnesium that
form soap scum. It still has all the carbonate that forms scale. I don't
drink "soft" water and I don't put it in my radiator. I'm also puzzled why
Jay thinks that reverse osmosis water is better than DI/Distilled water. Why
would the method of removing the dissolved mineral matter?
Bob
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