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Patterns at Tops of Parts in Electroless Nickel Tanks

Q. We are experiencing a rather unique problem in our mid-phos EN solutions that has me ready to make hand sanitizer for the rest of my life and forget metal finishing. Patterns in the plating ON TOP of the parts only. These are new plating tanks; we just opened in our new facility last October. They are 355 gallon tanks; 72" x 30" x 38" and are circulated using a 1.5 hp motor running through 2 heat exchangers, 1 micron PP filter bags and dried air sparging. I have always thought that selective patterning on parts in an EN tank was indicative of agitation problems but I guess it could be tank design. Starting to think that the good Lord just wants me to get out of plating all together. Freaky. Thanks everyone.

Randall Fowler
Cleveland, Tennessee, USA

June 29, 2020

A. Before you make conclusion of patterns on top of the part, you need to do the following:
1. jig the same part upside down to see patterns if any;
2. Plate a different geometry part to see patterns if any.
John hu

John hu
- Singapore
June 25, 2020

A. Randall,
Maybe if we could see these patterns it would help. My first thought is that it is an agitation problem, or at least related to the electrolyte flow. Maybe the top of your parts is in line with the in-flow pipe from the filter/pump system and this is creating turbulence that is reflected in the deposit morphology. Similarly, could the tops of your parts be too close to the electrolyte surface and any extraction or busbar agitation is creating localised turbulence on the top surface.
You do not mention whether you use ultrasonics as agitation - there are some reports of ultrasonics changing the morphology of electroless nickel deposits; this suggests that U/S alters the nickel deposition mechanism.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
July 1, 2020

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