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Problems with pitting


I have ~300 ltrs of electrolyte in my nickel plating bath.
I have been having some serious trouble over the past months with pitting, and we tried to resolve by changing the bath from Pulse reverse plating to DC Plating. By doing so, I had to add some additives, A5 + PB-N1.
I recently got an Analytical report done on my bath, with some interesting readings. It said that I had 32.2ml/l of A5 additive, but this could not be as I have only added 3 ltrs over the course of 2 months. I contacted the company that carried out the test, and they re-checked and came back with the same result. They think I could have too much saccharin in the bath ! Is there any way of removing such a large quantity !
And any suggestions on the pitting would be welcome. We plate on a 20x20 inch flat mandrel, with the bath size the same.
Constituents are Nickel content~89g/l
Nickel sulphamate ~448g/l
Nickel chloride ~5g/l
Boric Acid ~ 55g/l

- Scotland

Well Gary, you have a few of us at a loss as we have no clue what your additives are.
I do have some questions: Why do you have saccharin in a sulfamate bath. It is difficult to maintain it at a reasonable level to not take the nickel plate terribly compressive.
Next you say that you plate a 20" x20" mandrel in the same size tank. Since you have 300 liters that would be a much bigger tank. I know, the 3rd dimension was not given.
Now to your pitting problem. Assuming a proper preplate cycle, the pitting would seem to come from the nickel tank. Pitting in the plate is common when there is a lack of air agitation and or low anti-pit. If you are plating with a rational ASF, you should not be pitting the metal. You are overlooking something in what you have passed on to us.
Also, describe the size, location and quantity of the pits.

James Watts
- Navarre, Florida

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