Watts Nickel Plating Problem: pH is too high. Why? How to Fix?
If your problem is the opposite, please see Letter 23867, "Watts Nickel Plating Problem: pH is too low. Why? How to Fix?"
Q. Too high pH (more than 5.0) in Watts Nickel plating bath! I have problem with pH in Ni bath. To bring down I use sulfuric acid, but I am sure how to calculate additions.
electrical components mfgr. - San Jose, California
A. I would keep pH probe in bath and a dosing pump which will add as soon as pH increases. Continuous dosing will control bath better. By the way how much pH are you maintaining? 5 is too high for Watts bath.Payal Mag
- Charlotte, North Carolina
A. Calculate additions?
The normal way is to add small amounts 1/4 ml/L mix well (four hours or so) then see what has happened.
There is the problem that the boric acid acts as a buffer so you will add acid and see little change.
Do not get tempted to go overboard with the amounts added.
Keep a notebook of what is being added and the effect so if it happens again you can make the equivalent of several additions at once. (If you do this once more do not go over board with the additions).
surface treatment shop - Stroud, Glos, England
A. Dear Beningna,
You can try this :
1) Take a liter of your sample solution (pH 5)
2) Add H2SO4 in small measured amount to, say, pH 4.5
3) Now interpolate this amount of H2SO4 added to your 1 liter samples solution to your actual bath volume. You would have the actual quantity of H2SO4 to be added to your bath to bring down pH to 4.5
4)Add in, say, 3 installments and constantly check your pH.
It works for me, good luck!
Regards,Cheah Sin Kooi
A. All of the previous answers are good guidance. I just wanted to point out that sometimes I suggest using dilute hydrochloric acid (reagent grade) instead of dilute sulfuric acid. The reason is that it is one way of maintaining the nickel chloride in the solution while lessening additions of nickel salts. Further, if sulfate is rising, it allows an alternative.Gene Packman
process supplier - Great Neck, New York
December 30, 2013
We have a Watts nickel plating baths for fiber plating purpose. It is jigging process.
We are maintaining the pH at 2.2 - 2.7. To adjust the pH we are adding H2SO4 and HCl with the ratio 1:1.5%.
We are maintaining NiCl2 at 48-69 g/lts. But after adding HCl the NiCl2 is more than the required specification and it also increased the NiS04 g/lts. What should we do to avoid the situation? The bath is 5000 liters. We have 8 nickel plating baths containing the same liters.
- Hyderabad andhra pradesh,India
January 2, 2014
A. pH should be maintained at 3.9-4.5.
Use sulfuric acid to mauntain the pH, not hydrochloric.
Too high chlorides have a detrimental effect on ductility and while adding hydrocloric acid you cause corrosion of the equipment
chemical process supplier
January 2, 2014
A. Are you using bar anodes? What is the specification of your nickel anodes? Are you adding the acid directly over the anodes? Is the final pH within limits after you add the acid? Do you use anode bags? Do you have a lot of nickel precipitate on your anode bags above solution level until you add acid? What is the concentration of each of the sulfuric and hydrochloric acids before you mix them 1:1.5?
- OKC, Oklahoma, USA
January 3, 2014
A. Hello Sastri,
The reason your Ni metal is too high is because of the addition of HCl. As Sarah mentioned, you should not be adding HCl. The bath make up contains a certain level of NiCl2. Nickel chloride is in the bath to facilitate proper anode corrosion. If the chloride level is too high, your anode dissolution rate increases, in turn the Ni metal concentration in the bath rises. I was never a big fan of adding concentrated acids to lower ph values, you tend to over shoot your target. I have had success in adding a 10-20% dilution. Good Luck!
process engineer - Malone, New York
January 6, 2014
A. Sastry, You should not use hydrochloric acid to reduce the pH of a Watts bath - always use sulphuric acid. Hydrochloric acid will induce stress in your deposits and is very corrosive to most metals; its also smells! Also, never use concentrated acids - I would suggest 10% strength. Whenever you add acid to the bath, do is slowly and make sure the bath is well agitated. I am not sure why you see increases in both nickel sulphate and chloride when you add hydrochloric acid, but the way I analysed a nickel bath was to find the total nickel content and then the total chloride - this gives you they nickel chloride content and the rest of the nickel is sulphate. If you regularly need to alter the pH, this could be because there is insufficient boric acid, I would use about 30-35 g/l, although higher levels aren't particularly detrimental
R&D practical scientist
Chesham, Bucks, UK
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