Amol,
It could very well have been related to the exhausted Mixed Bed when the issue started. The higher the purity of the DI water, the closer the pH is to 7.0. If your feed water and/or recirculated water had a low pH (embedded CO2 or acidic flux residues in recirc water(?)), it would not have been buffered by the exhausted mixed bed and could have remained acidic.
-----Original Message-----
From: Kane, Amol (349) [mailto:[log in to unmask]]
Sent: Friday, June 04, 2010 7:40 AM
To: [log in to unmask]
Subject: Re: [TN] Connectors tarnishing after wash
Dear all,
Nothing has changed in the wash parameters. The water has an almost neutral Ph value. The problem seems to have disappeared as suddenly as it started. Based on what I see it may be:
(a) part issue
(b) changing the mixed bed tank somehow caused this issue (water too clean etc.,). Will keep a look out during the next change
(c) Ph changed due to changing out the mixed bed tank
Thank you all for your responses. Learned something new because of this situation.
Regards,
Amol
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Wednesday, June 02, 2010 11:26 PM
To: TechNet E-Mail Forum; Kane, Amol (349)
Subject: Re: [TN] Connectors tarnishing after wash
This is almost certainly an issue from the parts being too clean! When
drying, the exposed metal oxidises, producing your 'tarnish'. This is
usually a purely aesthetic problem and is often caused by evaporative
drying at a too-high temperature. It is better to use mechanical drying
at a lower temp.
Brian
Kane, Amol (349) wrote:
> Dear Technetters,
> Need some help from metallurgists out there. We have a connector that is tarnishing (turning black-blue) after washing in the water wash (straight up DI water). Almost looks like somebody colored the metal using a black/blue marker. The solder able surface of the connector (gold over Ni over Cu) as well as the plastic body is perfectly fine. From what I can find out, the connector part that is showing this color is steel with Ni plating. What in the DI water can cause this change? Our mixed-bed tank was exhausted when the issue surfaced (do not know if coincidental). With a new mixed bed, the tarnish is reduced, but still enough to cause rejections.
>
> Any help/pointers will be greatly appreciated.
>
> Thanks,
> Amol
>
>
>
>
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