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Stain on electroless nickel

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We manufactured chamber form carbon steel and plated it with electroless nickel. The size of the chamber is 1m on 1m on 1m. After the plating we find out that there is some fluidity marks on the plating. We cleaned the tank with ultrasonic cleaner and detergent.
The marks became stronger.
We tasted the chamber and find out that it is very clean but we can't use it with stains.
Please let me know if you familiar with this phenomena, how to avoid it in the feature and if there is something that I can do now to clean the stains.

Moshe Ben
development - Israel

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Stains can come from insufficient or contaminated final rinse or unbalanced (old) bath. Once developed they are very difficult to remove, specially from such a small part. Verify rinse quality (if desperate make it a little alkaline to neutralize any drag).

Guillermo Marrufo
Monterrey, NL, Mexico

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Have you tried sanding the surfaces with a 400 grain sand paper. This should work, since the stains are within the first few microns.

If you polish with white color (very fine aluminum oxide particles with wax) polishing compund, all the stains will disappear, but you will have a bright item. If you don't like it bright, then you can resand, this time with 600 grain sand paper, and get a semi bright finish without stains.

I wish good luck.

Best regards,

Amnon Vadasz
- San Antonio de Los Altos, Edo. Miranda, Venezuela