Electric Heaters for Plating Tanks are Becoming Plated

A. Hi, Ron.

The problem isn't that the heaters are grounded, it's that the anodes or cathodes are :-)

Electric heaters must be grounded for safety reasons, but this necessitates that everything else must "float", i.e., be isolated from ground; otherwise current will flow to or from the grounded heater to whichever side of the circuit is not grounded.

A. Make sure the heater surface is non conducting. If it is an electrical heater, they are usually covered with a teflon surface. If this surface is punctured somehow, an earth leakage will occur and trip the fuse if present. I have seen in the past that if the earth leakage system is not working, a small AC current flow is going through the chemical solution and starts a deposit on the heater.

Do not worry too much about the rectifiers, since those are DC.

A. We run heat and cool through coil pacs utilizing LP steam and a cooling tower. It negates the issue of electrical problems from electric heaters. I believe it's more efficient also. Solution temps must be maintained at specific temps. Ambient temperature plays a large role on which temperatures stabilize at and temperatures like to bounce up and down with the ambient temperature. So much where I live that the temperatures are computer controlled.

A. Hi Mahboob. Something is desperately wrong with that electric heater! Heaters are supposed to be completely sealed so that there is no possibility of shock short of physically damaging the heater, and they should be grounded for safety as well.

A. Hi Mahboob,

What Ted says sounds right ... but then he's a plater, and I sure ain't.

But why don't you use a liquid filled heat exchanger? Such as made of PVDF which is good for 140 °C? Then you could pump hot water through it till the cows come home without any shocks.

Just a thought.

A. Hello again, Mahboob. Please try to contact a local (Pakistan or India) plating equipment supplier who can show you proper electric heaters for electroplating operations. These commercially available units are completely sealed so that no liquids can make contact with the electricity, and they are grounded as a safety precaution so that if a leak occurs and the internal parts which carry electricity get wet, the fuses will blow.

Unfortunately I cannot fully describe in detail the entire procedure for designing and building a proper electric heater from scratch; it is something you have to buy, not something you make. But once you see one you will understand exactly what is wrong with your present dangerous heaters.

Ted is right. If heaters are being used correctly they will not give an electric shock. It sounds like your whole wiring system is faulty. I suggest you get a qualified electrician to check out the whole system before someone gets seriously injured. Electricity, chemicals and people really don't make a safe combination!

A. We deleted the brand name of the controllers, but they are single-phase electronic type with RTD temperature probe and LED readout. Richard, the manufacturer must have a distributor in your area who can help you. Unfortunately, it can be tricky, but have your electrician start by making sure you have power in, that the DIP switches are set for RTD control, and by wiring a light bulb to the power out terminals of the controller. The light bulb doesn't need protection by level control or over-temperature and will let the electrician get the controller itself going.

A. I hate to point out the obvious, but are you sure the problem is in the controller and not the heater?

A. Mr Totter has a good point. I have had a few electric heaters overheat. A popular heater/controller supplier here in the US (name deleted, but I do kind of like them) that I bought them from pointed out that they have an overheat protection fuse in them (not a good idea to shut one off and then pump the tank out right away). The fuse once blown will not allow the circuit to be complete (i.e., no power to heater until you make the circuit complete). A competent electrician (or a handy maintenance man) should be able to tell pretty quick. DIP switch is also an easy check if you have the manual in front of you. It is pretty straight forward.

Good Luck I've Been There

From Lowenheim; item DE is a bipolar anode.

A. Hi Justin. For safety the heater must be grounded. There are only two possibilities I think:

1. Either the heater is functioning as a bipolar anode, or
2. The rectifier bussing is grounded on one side or the other.

If your heater or any metal object is positioned between the anode and the cathode, the plating or electrocleaning current prefers to travel through it, rather than through the solution, because the resistance of metal is much less than the resistance of the electrocleaning solution. Please see topic 829 for further details. This bipolar effect causes the metal object to release hydrogen on the side nearest the anode and oxygen on the side nearest the cathode.
Still, I'd expect this gassing to be relatively minor, and to probably not hurt anything.

I think it's more likely that one side or the other of your bussing is grounded. If so, the heater draws electricity just as if it were whichever electrode is grounded. Good luck.

Regards,