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Understanding Watts bath operation

September 15, 2009

I have two questions on my mind and maybe somebody could help me with that

1)If anode efficiency is about near to 100% and cathode efficiency is 90 to 97% ussually. why a Watts bath decrease in nickel content.

It is supposed that it must increase its nickel content while it works...

How the anode to cathode ratio does play a role there? it does?

2) If I use nickel rounds type S and R(normal) type is there any problem?

One supplier says that type S round just can be used with S rounds only and if I mix them with normal electrolitic nickel it will become passive. That does not have sense for me.

Thanks for your time

Daniel Hernandez
Plating shop - Bucaramanga, Santander, Colombia

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First of two simultaneous responses -- September 16, 2009

For the first question, nickel will decrease due to drag out and water replacement, or passivated anodes, or too few anodes. In the too few, you are actually plating off of the anode baskets as an inert anode. The ratio is typically 1-1.
Reactivate your anodes and see if that helps.

S rounds are sulfur depolarised and I am not aware of anyone that recommends them for a watts bath.

James Watts
- Navarre, Florida

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Second of two simultaneous responses -- September 17, 2009

Daniel,
I like to use rolled depolarized 99% Ni anodes, bagged. Anode to cathode area should be no less than 1:1. There are other simple things you can check and adjust.
1) Make sure the chloride content is not too high. It plays an important role in anode corrosion.
2) Keep your ph on the low side 4.0 to 4.2
3) Check your Ni metal deposition rates on your parts, keep anode bars clean.

Mark Baker
Fellow Plater - Syracuse, NY, USA

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September 19, 2009

Well first thanks to the people took the time to read this, so the answer is that anode to cathode ratio plays a role in th amount of nickel that is dissolved against the nickel that is deposied.

My chloride is to high, it is in 63gr/lt normal is 45-40 gr/lt, that promotes anode corrosion but too high chloride cause too stressed deposit.

Is any way to reduce chloride level?

DANIEL HERNANDEZ
- Bucaramanga, Santander, Colombia

A very touchy way would be to try adding barium sulphate as it will precipitate the barium chloride. do it off line and let it settle and filter it back into the tank. I would try it in a hull cell first. Do not get in a big rush in doing it or you will have an even bigger mess.

James Watts
- Navarre, Florida
September 21, 2009

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September 23, 2009

Hello, :-)

well, to drop down the chloride content in a nickel solution it is not necessary make a fall-out with barium carbonate o any other similar reactives. You can avoid this if you use diluted sulfuric acid to adjust your pH instead of hydrochloride acid. I suggest you use both of them depends on content of sulphate vs chloride.

Best regards,
Dominik

Dominik Michalek
- Mexico City, Mexico

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First of two simultaneous responses --

I assumed that anyone running a Watts tank would use sulfuric to adjust the pH. The source of the chloride is either poor water for make up and rinse tanks Or from drag in fron a muriatic acid activation/pickle.

Another way to fix it is to decant as much of the tank that is needed and make up the balance with fresh solution. You can use the old solution for make up as you need nickel and chloride.

James Watts
- Navarre, Florida
September 24, 2009

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Second of two simultaneous responses -- September 25, 2009

James and Dominik,

Are you sure about this? I have some 10% Barium chloride sat on the bench in my lab right now. I use it for sulphate determinations. Barium sulphate is insoluble in solution and will not precipitate out a chloride, barium carbonate will react wil the acid, so if it is a sulfuric based solution you will precipitate out barium sulphate, if a chloride you will only create a barium chloride solution in the tank.

The only effective way of reducing chlorides is to carry out a partial discard, analyse and replenish anything that has gone low.

Brian Terry
Aerospace - Yeovil, Somerset, UK

Brian--My bad, your are correct. In a senior moment, I turned them around. Jim

James Watts
- Navarre, Florida
September 25, 2009

Thanks for your help Thanks to all

DANIEL HERNANDEZ
- Bucaramanga, Santander, Colombia
September 30, 2009