On 7/11/02 12:41 AM, "[log in to unmask]" <[log in to unmask]>
wrote:
> DI Water itself is not corrosive, but it is aggressive, if you get the
> difference. Having been stripped of all it's ionic content, it's "hungry"
> to replace those ions, and will draw them from wherever it can. That's what
> makes it so effective at removing ionic contamination from boards. However,
> it doesn't discriminate about where it draws ions from, and draws them just
> as readily from seals and gaskets if it can. Domestic appliance seals are
> not resistant to this sort of attack, and the loss of ionic content from
> their composition degrades them to the point where they fall apart and dump
> more dirt back onto boards than is ever removed. The machines then leak and
> eventually become useless for anything.
>
> Peter
>
>
> Rudy Sedlak <[log in to unmask]> 10/07/2002 09:08 PM
> Sent by: TechNet <[log in to unmask]>
>
> Please respond to "TechNet E-Mail Forum."; Please respond to RSedlak
>
> To: [log in to unmask]
> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
> Subject: Re: [TN] Water soluble batch washers.../deionized water
>
>
>
>
>
>
>
>
> The "hazards" of deionized water are somewhat blown out of proportion.
>
> Deionized water is not really that corrosive, only marginally more than tap
> water...
> HOWEVER, deionized water lacks the buffering capacity of tap water. (All
> that water hardness serves to buffer the pH nicely) So, if the "stuff"
> you are rinsing is corrosive inherently, the deionized water also becomes
> corrosive, especially to metals.
>
> However, most of the aqueous cleaners are pretty mild and non-corrosive, so
> rinsing them with deionized water should be safe, even for the common home
> dishwasher.
>
> This is assuming that the ratio of (acidic/corrosive) flux on the parts in
> the washer to the amount of alkaline cleaner being used is not so bad that
> the wash water becomes acidic...then you have BIG problem.
>
> The answer is to clean just a few boards, OR use a lot of cleaner to keep
> the pH above 9, and preferably higher than that...
>
> Rudy Sedlak
> RD Chemical Company
>
>
>
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Techies,
As Peter said, De-ionised water is aggressive. It will leach carbon from
welds and over time, degrades stainless steel for the same reason - as was
discovered by the Nuclear Power industry when they found reactor vessels
breaking down.....but that would be somewhat more of a problem than a
scrapped dishwasher!
--
Regards, Graham Naisbitt
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