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Pitting problem in nickel sulfamate bath

We have pitting problem in our nickel sulfamate bath, we check: concentrations, pH, all is OK, agitation too, but until the moment we have not been able to correct the pitting we made several tests with the cleaning, activation and for last the base material in the low steel (AMS 5040) still appear pitting, we activate with HCL, and a second test with H2SO4 with both still appear pitting. After we treat with stainless steel, activate it with HCl and the part doesn't have pitting this is very good. I'm thinking that activate the AMS 5040 with HCl is not good idea, somebody help me with this maybe I have to activate on another form.

Thanks in advance.

Iztchel Villeda
process planner - Mexico
November 26, 2009

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Try activating with a weaker solution.
You do not mention the use of any wetting agent (anti pit material). Your agitation may not be quite enough.

James Watts
- Navarre, Florida
December 1, 2009

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Try adding some surfactant, if not already in your bath. If it is there, check the concentration.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
December 9, 2009

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Where is the pitting located?
If it is mainly on the high current density area, it is lack of wetting agent but if it is shelf pitting (on the upper side of the parts, it means that the solution is not filtered properly.
I hope you have continuous carbon filter of solution.

Sara Michaeli
Tel-Aviv-Yafo, Israel
December 10, 2009