The authoritative public forum
  for Metal Finishing since 1989
  

  -----

pH increases too fast

Hi all,

I encounter a problem, any one can tell me what is the root cause and how to solve?

Ni plating PH value keeps increase 0.1 unit/day, I have to add Acid to lower it down. but the Boric acid anode corride agent content are all within vendor recommended spec

Thanks

Henry ng
plating shop employee - Singapore
2007

Boric acid is a buffer that has three different pH value that it tries to hold. If you are between these pH values, it will not do much except it's primary function of not letting the pH at the part surface go totally berserk. The heavier that you use the tank, the faster the pH will change. You can develop an amount of acid to add per amp hour of plating so that you will not have to analyze every day. Ph is so simple to do, why not just check and adjust.

James Watts
- Navarre, Florida
2007

---

The pH of a bath will naturally increase as it is used because hydrogen is discharged at the cathode, thereby reducing the acidity level. You give no indications as to how large your tank is or what throughput you have, so to say 0.1 units per day is pretty uninformative. I would suggest that for a conventional plating bath this is good control; - most baths operate within a range of, say, 4.2-4.6, so to hold it within 0.1 over a day could be quite good. I would suggest you check your bath every day, or even every shift, and make the modest additions that may be needed. I am of the opinion you have nothing to really worry about.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2007

---

All the above advice is correct, but from a practical point any analysis/test should be to CONFIRM that what has been added/done is correct, not add to make it correct, otherwise the process is always out of balance and the test result gets it back only nearly to balance as there is always a time delay, particularly if done by an outside source like a supply house.
Therefore my suggestion is to monitor what addition is necessary over say a week or a certain number of days and add the average amount calculated for say half a day and add that every half day and your pH check then is to confirm that that is the correct addition. If not modify the average addition. This should apply to all maintenance additions, basics and brighteners.
(This also makes the plater feel he is in control of the process if the analysis result is what the data sheet says)

Geoffrey Whitelaw
- Port Melbourne, Australia
2007