Along the same lines, Jim Maguire, in his Boeing years, had humidity
chambers fed with 18 megohm water. After a short time, they found these
stainless steel needles on products undergoing humidity testing. The 18
meg water attacked the stainless steel. They changed to 8-10 meg water and
the problem did not repeat.
I agree with what others have said, that once stainless steel starts
rusting, it will continue to do so until you re-passivate the surface. I
have had it done on stainles steel panels from humidity testing using
fuming red nitric acid. Nasty naaaaaasty process.
Doug Pauls
Brian Ellis
<b_ellis@PROTONIQ To: [log in to unmask]
UE.COM> cc:
Sent by: TechNet Subject: Re: [TN] Rust (corrosion) Removal from sheet metal - Need urgent help.
<TechNet@listserv
.ipc.org>
05/30/2003 06:09
AM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to Brian
Ellis
Is that why there are so many PCB fab shops in Phoenix, Rudy? :-)
Different phenomenon than red plague, though, which happens only with 18
meg water. And it doesn't matter whether the metal is passivated or not.
However, low-carbon stainless steels are less prone to it. No one knows
why, to the best of my knowledge. I've seen it occasionally in our old
cleaning machines. We got round it by adding a metered bypass round the
water purification to reduce the resitivity from 18 to ~10 megohm-cm.
Brian
Rudy Sedlak wrote:
> In a message dated 5.29.03 11:45:23 PM Pacific Daylight Time,
> [log in to unmask] writes:
>
> And Rudy adds edits....<grinning>
>
>> You may not know it, but even very pure water will attack stainless
>> <non-passivated> stainless steel, producing "red plague". In fact,
>> this is a fine iron-rust powder that adheres to the surface, but can
>> be wiped off. <Some>Tap water<s> will not do this....
>
>
>
> Brian have you spent much time in Phoenix Arizona? The tap water there
> is so high in Chloride that it can be used to etch
> metals....---------------------------------------------------
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