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topic 5370

Autocatalytic Ni/P - Precipitation


I am looking for some tips on eliminating nickel precipitation from autocatalytic Ni/P bath. We are not a plating shop but we do very small batches of Ni/P for our own purposes and often the Ni precipitates even before parts are processed. We monitor quality of DI water, pH, bath is run through filters, etc. Where shall I start looking for the root cause ? ... . I'd appreciate some tips. Mariusz de Georgel

Mariusz de Georgel
- Toronto, Canada


Firstly, how often are you using the NiP? If you have it at operating temperature a lot but are not using it often, this can easily cause precipitation. Secondly, what kind of tanks are you using, and have they been properly prepared? They need to be leached before initial use and then passivated with 30% nitric acid followed by neutralisation with ammonia or potassium carbonate solution before refilling with solution. What type of heaters do you use? If they are 316 stainless steel they need to be passivated at 40 °C in 30% nitric. And how is the temperature controlled? If the temperature regularly gets above the maximum operational point (usu 90-93 °C), precipitation may readily occur.

John Reid
CP Plating - Brisbane, Qld, Australia

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