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Conductivity control issues for plating rinse tanks

If using a conductivity controller to control the amount of rinse flow, what are the suggested practical set points. This could vary with the conductivity of the incoming water, in this case the city water is about 70uS/cm.

Is this related to a certain concentration (like say 0.1%) of the process being rinsed. Is it different depending whether it is in the cleaning cycle or prior to entry to e.g. the nickel tank.

I am involved with a water/energy saving project for about 20 plating companies and want to suggest the use of conductivity as a means of cutting back water flow but need some guidance on practical conductivity measurements, or the practicality of same. Have been taking measurements with a $140 handheld meter and the results are really interesting. I am thinking every plating shop should have one, otherwise how do you know how much flow to use, or even when do you need to turn the water on, maybe not till a number of racks have been processed.

Geoffrey Whitelaw
Geoffrey Whitelaw
- Port Melbourne, Australia


As they say, you can't control what you don't measure, so conductivity meters may well be a good investment. But first I think they should look at Kushner's "Water and Waste Control for the Plating Shop" [adv: this book on eBay, Amazon, AbeBooks] :-)

I don't think you'll find the "presets" you are looking for. That's because, while contaminants do increase conductivity, individual contaminants vary both in their conductivity and their damage to the baths. So it's quite empirical and based on the particular plating step and plating process, as well as the conductivity of the makeup water.

The best starting point might be the rough rule of thumb that the rinses must dilute the bath by a factor of 500 to a thousand. So put 1 part in 500 of the solution into a beaker of makeup water and see how that measures and how it looks, and whether it would be satisfactory as the final rinse after that process.

There was a great tip in one of the plating magazines this month! Don't plumb your rinse line to the bottom of the tank, instead install a larger diameter "stand pipe" to the bottom. Then have your rinse line stop a couple of inches above this stand pipe. This allows you to both see the flow and to stick a beaker in to measure it at any time.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

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