Electroless nickel plating problem

[AligatorAmy]

Hi,
I have a 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 enforce 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 1.5V for approx. 2min 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 turn 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 (in closed container with all ingridients mixed, ready to use).

Did anyone came across something similar?

P.S.
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 a 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.
Regards.

 

[Achy47]

Thank you for sharing your experience with electroless nickel plating on brass components. As a scientist familiar with plating processes, I would like to offer some insights and potential solutions to your issue.

Firstly, it is important to note that electroless nickel plating is a chemical process, not an electrical one like electroplating. This means that the deposition of nickel onto the brass surface is driven by a chemical reaction, rather than an electrical current. Therefore, the use of DC power may not be necessary for the plating to occur.

Based on your description, it seems that the main issue you are facing is the complex geometry of the brass components. This can indeed be a challenge for electroless nickel plating, as the solution needs to reach all areas of the surface in order for the plating to occur evenly. Your use of air agitation and a special jig is a good start, but it may also be worth considering other techniques such as ultrasonic agitation or rotating the components in the solution.

Additionally, the fact that you are only able to get the nickel plating when the DC power is turned on suggests that there may be an issue with the plating solution itself. As you mentioned, the solution was stored for 3 months before use, which could have resulted in some changes in its composition. I would recommend checking the solution's pH and concentration of nickel and other components, and adjusting them if necessary. It is also possible that there is some contamination in the solution, which could be causing the unexpected red color on the brass surface. Make sure to filter the solution before use and avoid any contact with other metals.

In conclusion, I would suggest experimenting with different agitation techniques and checking the composition of the plating solution to see if that helps with the uniformity of the nickel plating on your brass components. If the issue persists, it may be worth seeking the advice of a professional plating company or conducting further research on the specific properties of brass and electroless nickel plating. I hope this helps and wish you success in your plating endeavors.