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topic 4221

Heating and Cooling of Chrome Plating Tanks


(2000)

Q. Dear Reader,

I am a worker in an electroplating Shop. Recently we are planning to purchase cooling systems for chrome plating tanks. We need information about cooling equipment. Presently on large sized parts, with high current densities the tanks heats up even when the if the heaters are tripped off. The solution temperature rises and solution boils. Hence at higher currents the tanks need to be cooled rather than heated. I would appreciate guidance from you

Thanking you in anticipation.

Najeeb

Muhammad Najeeb
- Karachi, Pakistan


(2000)

A. Dear Mr. Najeeb,

As a hardchrome plating company with many years of experience, we feel that we might be able to help you. There are many different solutions for your problem, but in order to be able to help you, we would like to receive more detailed information, such as:

Tank size,

catalyst condition (density, Fe, Cr3+, etc.)

Rectifier capacity

If you give us this information, we will work out a detailed plan for you.

Kind regards,

Roel Jaarsma
- Hengelo The Netherlands


(2000)

A. Hi Nageeb,

I guess that you have 3 options: 1. Use a much larger tank; 2. Use a cooling coil (PVDF should be ideal) which is the normal approach, I believe; 3. Use what I call 'evaporative control'.

Back in 1980 I encountered exactly the same problem. The customer in Vancouver, EBCO, was plating very large diameter rolls and the heat became excessive which, possibly (I am not a plater!) might lead to a poor finish.

EBCO still have this system. However, at that time in 1980 they wanted to do something about the air pollution, too.

That's where I came in. I suggested what I call an ordinary 12 micron chromic 'dry scrubber' mist eliminator (fairly sophisticated internal design!) which has two banks of PVC blades. I suggested (but I had never every heard of this being done before) that the eliminator would have the second blade bank separated and with its own washdown bank ... and that they use a pump to spray the first blade bank with the hot chrome. (I have over 300,000 cfm of hard chrome scrubbing fully annotated).

What happens then is that the ambient air (Boyle's law?) draws off the heat from the tank's hot liquid which is returned, definitely cooler!, via gravity back to the tank.

If you wanted to corroborate this, let me know and I could give you the address & contact at EBCO. OK? Last year they did replace one of the blade banks -- not bad for 20 years service)

Cheers!

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).




Chrome plating tank heating/mixing

(2000)

Q. Hi, I am working on chromium plating for my thesis. I have a question regarding air sparging in hard chrome plating. Is it mandatory to sparge air? If yes, what is it for - mixing or heat removal? Or on the other hand, is the typical plating load enough to maintain the temperature of the plating tank or external heater is needed to maintain the temp?

Susheel Yadav
University of Cincinnati - Cincinnati, Ohio


(2000)

A. Best practice is certainly to include heating because the bath operates at 110 to 130 °F. (depending on exactly what you are doing) and you do not want to use your rectifier and your chrome plating solution as a heater. Best practice is also to include cooling coils. The air would be used for solution mixing rather than cooling, particularly if the tank is deep.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



October 9, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hello!

Someone has told me that the chrome bath is heated during plating time. So after each plating process it has to be cooled back down to 45 °C. Is this correct or not?
Thanks for any answers!

Bojan Koren
- Bovec, Slovenia


October 2014

A. Hi Bojan. You are trying to operate the chrome plating tank at 45 °C, so you must do what is necessary to keep it at 45 °C. That means providing heat if the bath falls below 45 °C, and removing heat (providing cooling) if the bath exceeds 45 °C ...

If the bath runs 24 hours a day, and it processes a reasonable amount of production, it is possible that separate heating provision may not be required because the rectifier will provide more than enough heat (but it's still desirable). If the bath operates frequently or constantly, it will probably be necessary to remove heat with cooling coils, or the tank will overheat. Stopping production to let the tank cool off is rarely a satisfactory answer. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


October 16, 2014

Q. Thanks for your answer. The chromium baths does not heated during plating time because of chemical reactions if i'm correct?
In my opinion that man was wrong, when he said that when the electric current goes through chromium electrolyte and the reactions takes place the bath get heated and it's necessary to cool it down to 45 °C. He is not a chemist and he doesn't know much about this, but he has much more experience then me so i wanted to get opinion from someone else also.

I was measuring the temp. in chromium baths now for 3 days and the temp. is constant from 42 to 46. but about half a meter deeper the temp drops to 40-41. Can this cause a burned or dull deposit if the temparature is below 42?

Bojan Koren [returning]
- Bovec, Slovenia


October 2014

A. Hi. The temperature must be constant while you are plating: all the time and at all depths.

It is not true that having the heating on while plating will cause a problem. Rather, it is true that the plating generates so much heat that additional heating may not be required during that time, and cooling may be required to keep the temperature from climbing. If you multiply the plating Amps you are using times the plating Volts you are using, you know the Watts of heat you are adding to the bath.

A range of 42 - 46°C is too much variation. I think you should not exceed the range of 43 -44 °F for most consistent plating. Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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