Help with high concentration of Calcium in a bright Nickel bath

A. It looks like you use city water for make up as well as rinsing. Switch over to D.I. water. Have you noticed any deterioration in product properties or plating defect? The tolerance on upper limits on calcium is quite high. Can you do regular or bulk removal and replace with fresh solution?

A. Your figure of 22,000 ppm looks as if it is the solubility limit of calcium sulphate. I would therefore surmise that you have a fine suspension of calcium sulphate in your plating bath and this is causing your pitting as mentioned above. I would recommend a few things, such as using a filtration rate of at least 6-8 tank volumes per hour. The filter size should be at least 1 micron, but remember, as you use the filter, the pores get blocked and the effective pore size decreases, making it a better filtration system, but causes an increase in pump pressure. Secondly, I would be very careful heating your nickel bath to 80 °C if the bath is based on sulphamate. At this temperature it starts to break down to Ammonium and sulphate ions and increases the stress of the deposit. If it is a sulphate or chloride bath, there is no problem.

Thirdly, if there is a lot of calcium sulphate in suspension, there could be a problem with the balance of your additives as these could be adsorbed onto the calcium sulphate and ultimately precipitated out.

Fourthly, I suspect you are using city water, so I suggest you invest in a water treatment unit, such as a de-ionising unit or at least a softening unit. The best is probably reverse osmosis, but thus can be expensive. The down side of a softener is that it may increase your chloride levels and induce stress, but perhaps this is not a problem to you.

Fifthly, bifluoride is highly toxic and should be used with great care, so check your MSDS for best practices. Also check your water treatment plant's ability to treat it. If you don't have one, check with the water treatment company for acceptable fluoride discharge levels.

Finally, I would suggest you replace the nickel bath. If this is too expensive, the second best alternative is to bleed off some electrolyte and replace it piecemeal, but this can also be expensive on consumables. You could batch treat the bleed-off, but that too can be expensive in manpower.

I would not suggest you use town water to rinse, as this can cause staining - it is better to use counter flow rinsing with good clean water (e.g., DI or RO) in the final rinse. This principle has been well discussed on this website.

A. First of all determine whether it is the nickel or the chromium giving the haze. Until you know that you will only be guessing. Just have a look at the parts after each process. Then check the bath compositions to make sure they are in spec. Adjust as required. Check all your power leads and repair faulty or damaged ones. Hopefully you have removed most of your calcium by now - this may have caused the nickel bath to go right out of spec, especially with regard to brighteners and levelers. I have never seen calcium cause haziness, but that doesn't help you, unless you are depositing a composite of insoluble calcium salts and nickel.

A. My reference had the temperature to filter for calcium at 155 F, I am sure that this had to do with the temperature which all the plastic linings, filters, tubing, etc. had to withstand during the treatment. If you can control the temperature closely at 140 F , within 5 degrees F, after that, you could probably keep your bath in operation.

The haze you are seeing could be calcium, I called it "stardust" because the haze does look like a cloud of distant stars you might see in a photo of the heavens. See my article for more on troubleshooting bright nickel.

A. We have found that by keeping the sulphate concentration in the chrome pre dip tank slightly high the haziness in the parts go away.