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topic 37785

Electroless Nickel Plating: "Metal Turn Overs?"

A discussion started in 2005 but continuing through 2017


Q. Our shop is thinking about offering electroless nickel to our customers. I've been reading up on it, but I haven't seen a definition of "metal turn overs". I'd appreciate some insight on this term.

Ray Roberson
RKL Enterprises - Eads, Tennessee, USA


A. Hopefully someone will correct or fine tune my explanation, Ray, but . . .

As you consume the metal in your electroless nickel bath you have to replace it, of course. When the total additions of replacement metal you have added are equal to the total amount of metal originally in the bath, that's one metal turnover. When the total of metal additions you have made is 5 times the amount of metal in the original makeup, that's 5 turnovers.

The reason the term is important is that in addition to consuming metal, the process generates spent reducer and other contaminants that cannot be practically removed, and eventually foul the bath so badly that you cannot continue to use it and must dump it. One measure of the value of an electroless nickel process is how many turnovers you can do before replacement is necessary.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


A. The only thing I would add is that you cannot necessarily compute metal turnovers by volume. Many suppliers sell a bath make-up solution and a replenisher solution, and the metal content of these solutions is not the same. You have to ask the supplier about calculating the MTO's (or back calculate them from the replenishment scheme yourself).

James Totter
James Totter, CEF
- Tallahassee, Florida

EN Ni-P plating works by DC supply only

July 30, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi,
I have brass components (brass grade CZ121) which require electroless nickel plating (not electroplating).
I cannot get electroless nickel coating for my brass component from regular coating companies because of its complex geometry. Along with air agitation, special jig is required to force the coating solution to flow through intricate geometry of the substrate. I do it in the lab (I need this for rapid prototyping).
I use DC 1.5 V for approx. 2 minutes to kick off the process (+ goes to nickel cathode and - goes to brass).

However, I can get NI-P coating only when I keep DC turned ON. Once I turn off DC power then coating stops (checked experimentally for a few brass plates).
The coating solution was provided by regular Ni-P coating company.
I suspect that the problem may constitute the fact that Ni-P coating solution was stored unused for 3 months (with all ingredients mixed, ready to use).

Has anyone come across something similar?

If DC power is applied only for first 2 minutes of the process then after next 15 minutes of keeping brass in coating solution the substrate surface has red colour (it is supposed to have silver colour).
It seems that either copper is being deposited on substrate (there is a brass or bronze component of the tank heater which is submerged in the solution) or some element is dissolved from substrate surface (zinc?) leaving mainly copper there).

Please help.

Hubert Wittke
- Limerick, Co. Limerick, Ireland

Electroless Plating
bt Mallory & Hajdu

from Abe Books
info on Amazon

July 2017

Hi Hubert. We appended your inquiry to a thread with food for thought: Electroless nickel baths are complicated, and can become exhausted. If I read correctly, you got the solution from a plating shop; that's not the right approach: you should get it from an electroless nickel process supplier complete with operating details.

Your brass heater is a "no go". You need to get a heater made of teflon or other inert material. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

July 30, 2017

Q. Hi All,
Thank you for your responses.
To answer your questions:
- The plating solution (ready to use in a closed bottle) has been provided by a company which does electroless nickel plating service.
- The electroless nickel plating process did not 'want' to start for me even for 'fresh', unused solution.
My concern is that the solution, once delivered by mentioned company, was stored unused in a closed bottle for 3 months, before I started using it. I am not sure but it could perhaps degrade chemically somehow, within these 3 months?
- My heater is made of stainless steel, it is only a flange for fixing it to the tank which is made of brass. I did not get it coated with teflon, because I use 12VDC heater (for safety). 12VDC heaters covered with teflon are difficult to obtain on the market. The only suppliers I had found out are in China but they sell only large numbers. Teflon coating in own range or by a company may pose problems (time and equal teflon coating layer- thus I do not want to go there unless absolutely necessary).

Hubert Wittke
- Limerick, Co. Limerick, Ireland

August 10, 2017

A. Hi Hubert,

From my experience storage of the solution is no problem. Electroless Ni operation is done at temperature near boiling, so below about 70 °C no reaction is anticipated. I use Ni as functional coating with very limited area to plate. We have seen bath idle times of 2 month between plating jobs and had zero problems after reconditioning of the plating line before a new job. Maybe that's a point to investigate for yourself: as pointed out by Ted, you really should understand how to prepare a bath and what measurements are important. E-Ni is not for "plug and play", but once you understand whats important to monitor, you can recondition a bath in a little over one hour.

I could not think of a specific reason for your solution to decompose while stored, but on the other hand probably nobody would use old untested solution of they are not able to see if the chemical concentrations are within the specifications of the supplier.

I have enjoyed to read the posts over here for quiet some time and hope i can contribute a little bit by sharing my opinion. :)

M. Noack
- Berlin, Germany

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