Zinc contamination in nickel tank

Q: How can I reduce nickel plating defects over zinc die-cast substrate? 

A: In the case of zinc die-cast the substrate is directly responsible for introducing zinc contamination to the nickel tank. Zinc is a toxin to nickel plating baths and will significantly reduce performance and bath life. It is important to address this issue early in the process which is typically:

- surface prep
- copper plate
- nickel plate
- post treatment

The best corrective action is
to ensure sufficient coverage during copper plate to seal the substrate and prevent it from dissolving in later process steps. However, small IDs and complex part geometries make this difficult in many cases. The next focus is treating the nickel tank itself. There are at least 2 options.

The first option is to install a purification unit on the nickel tank which utilizes an ion specific resin to remove zinc from the bath. This is preferred by manufacturers doing high volume production as the economic gains from a longer lasting bath and greater plating performance more than pay for the capital equipment and variable operating cost of the unit.

If plating volume is not sufficient to justify such an investment there are ‘service additives’ available to treat the zinc in the nickel tank. These service additives essentially tie up zinc in the nickel tank and prevent it from interfering with the plating. These additives can become costly as production volume increases. Choosing the proper method depends upon the individual capabilities and economics at the facility.

Always try and solve the root cause by talking to a technical service representative from a plating supplier. For further technical assistance feel free to send me an email at sandrew@enthone.com

Additional information can be found here http://www.pfonline.com/articles/plate-better-longer