Alkaline Zinc: Ensuring a Bright Solution without Sacrifice

“Get my alkaline zinc bath brighter” is a common request by customers looking to improve their zinc baths. It is often followed“-and make sure that my bath does not sacrifice efficiency and throughput and continues to maintain consistent metal distribution over a range of current densities.”

Making an alkaline zinc bath brighter may seem straight forward enough. Just add more brightener and you’re all set, right?

In real-life applications, brightener additions can be extremely problematic for platers.

Today’s alkaline non-cyanide zinc technology is based exclusively on the use of synthesized complex polymers that are cationic in nature. They carry a positive charge on some portion of the polymeric chain and  These polymers provide brightening and leveling in addition to reducing the bath efficiency, especially at high current densities (HCD).

Maintaining HCD can be a double-edged sword in the plating process. On one hand, the polymeric-based brightener additions enable HCD deposition without burning. However, when too much brightener is added to the plating bath, the overall efficiency can be diminished significantly. This can lead to reduced plating seeds.

In the plater’s quest for a brighter product, it becomes very easy to overload the bath. Consequently, this lowers plating speed and overall productivity.

The following procedures can help your bright alkaline zinc plating bath deliver the brightest performance:

• Follow the operating and consumption guidelines as published in the supplier’s technical data sheet.

• When in doubt, laboratory testing can be performed by means of a Hull Cell and be a useful tool.

• Run a Hull cell of a new bath lab sample of the additive system being used. Pick two points approximately 0 This will establish a baseline and give a ratio of deposition in the HCD versus the LCD areas.

• Perform the same step on your working bath. If the ratios are close and the panel is of sufficient brightness, then no additional additive is necessary.

• If more brightness is needed, add the appropriate amount to the working bath in the Hull cell. Typically, this should increase the brightness. The thickness at the same HCD and LCD point should be taken and compared.  If that ratio is similar, then it is appropriate to add more additive.

• If the HCD thickness is significantly reduced, as indicated by a reduced Instead, a purifying material or water conditioner additive should be considered.

Key Insight: A Hull cell is a miniature electroplating cell used to test and diagnose problems in a larger electroplating bath.

Conclusion

With these procedures, you will be able to get customer’s zinc baths brighter and ensure that their bath does not sacrifice efficiency and throughput and continues to maintain consistent metal distribution over a range of current densities.”