21 Nov
2009
21 Nov
'09
11:59 a.m.
----- Original Message -----
From: "Guy Sotomayor" <ggs at shiresoft.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Saturday, November 21, 2009 1:36 PM
Subject: Re: Water damage
On Nov 21, 2009, at 9:16 AM, Pete Turnbull wrote:
Yes, ultra pure water is a very good solvent. When exposed to air it sucks
out the CO2 very quickly to make a weak acid (carbonic acid). Metals like
316SS will turn a goldish color over a period of use.
What you want for washing circuit boards is just RO (reverse osmosis) water,
basically most of the solids what are found in normal water are removed so
when it dries it does not leave a film (I think car washes have it for the
final spotless rinse). RO water can be de-ionized and ultra filtered to get
ultra pure water (along with UV lighting to kill bacterial that might be
growing in your pipes and more filters to pick up the exploded bits).
On 21/11/2009 16:54, dwight elvey wrote:
Water is often termed the ultimate solvent. H2O (the molecule) has some
interesting electrostatic properties that allows it to interact with a
lot of different materials (including most metals). It makes it appear
as if it has some acidic properties but it's not (ie it's not what one
would consider a chemical reaction...the dissolved material hasn't
chemically reacted with the water).
TTFN - Guy It isn't quite true that pure water won't
cause corrosion.
It is actually slightly acidic. I recall reading about
a large cosmic ray detector ( large pond of water ) where
the water was ultra pure. The metal pieces would often
just disolve.
That surprises me. Pure water, H2O, does partly dissociate, but in
doing so it forms an exactly equal number of OH- hydroxyl ions and H +
hydrogen ions -- the latter being what makes an acid acidic, and the
former being what makes an alkali alkaline. Pure water, in fact, is
virtually the definition of pH 7.0, which is absolutely neutral. I
suspect what's actually happened is that dissolved gasses made the water
acidic, but then it's not truly pure. For example, dissolving CO2 in
water makes carbonic acid.