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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