Power supply

[MarcoPau]

Hello there, I'm trying to set up some tanks for zinc, nickel and chrome (hope I can get Copy Chrome here in Italy...!). My first question is about the current, as I went to a galvanic laboratory and they told me they use a rectifier @ 4 V DC. I have the chance of getting a big rectifier (it's actually an industrial battery charger) @ 24 V DC, 100 Amp. Would that be something useful for my purpose or I definitely need less voltage? Is there maybe any easy (=cheap ) way of controlling the tension coming out of such a power supply? Otherwise I guess I am going to have to use car batteries with a rheostat, or find another rectifier...

Thanks for your very kind help! This forum is a knowledge mine!

[KCV6]

Marco,

you will need to go down to about 0.5Vdc for small zinc plated items. Range is about 0.5 to 1.5Vdc for Zinc. For copy Chrome the voltage range is around 2.0Vdc to 3.0Vdc.

If you are not doing real chrome then I would suggest a 0 to 5Vdc power supply.

As far a current is concerned, try to work out what you think the biggest part would be that you would plate in square inches of total surface area. multiply this by 0.1Vdc and this will give you roughly the maximum current you will ever require for plating.

I picked up a great 0.8Vdc to 15Vdc 60A power supply from a HAM radio (Amature radio) supplier for a very good price.

See the example in the link below.

Andrews Communications - Electronics

Note: Its the SP-9600 it says it is a 60A 1Vdc to 30Vdc. They actually go down to 0.8Vdc.

Cheers

Mark

[MarcoPau]

Thanks for the hint Mark! I will try to hang around a bit more and see if I can get something more appropriate, or maybe some diode bridge or rheostat that can turn down voltage out of this big cabinet that gives 100 A @ 24 V DC.
Or probably I will more easily go with batteries, and maybe set up an alternator led by an electric engine that keeps the charge? I guess there are many ways, the point is choosing the easiest and cheapest one

Anyway, I think the biggest things I'm gonna chrome (guess Copy Chrome will be mandatory, having read the current required for regular chrome! ) will be motorbike exhausts (average 60-80 cm long pipe, 10 cm diameter = ~25x4 inches), or, if I will ever set up something bigger, old cars bumpers...

Please let me know if you think I'd better go with batteries connected in parallel, as I can get 12 V car batteries for free at a junkyard's...

See yaaa

[MarcoPau]

Mark, I've been studying some basis of electricity in the past few days, and one thing you said I can't really understand: you say I will need certain voltage for certain plating processes but, according to what the Caswell manual says about controlling the current with bulbs or a rheostat (I will be building one using some dozens of meters of copper wire with the help of an electrician), the voltage is not really mentioned. And I've been thinking over this, finding that if I pick up a battery and fit a bulb into the circuit, after the bulb there will be no potential difference, and that's where the tank would be fit in the electroplating process. Now, the "tank" has virtually no resistance, thus the potential difference at its ends will be anyway close to zero.

We made a few counts, considering a 4V battery built by making bridges between the 2V elements 1,3,5 and 2,4,6 of a 12V car battery. Thus 1,3,5 in parallel giving together 2V, + other 2V of elements 2,4,6 = 4V:

if I want to have 10 amps going around I will have to use 56 meters of a 2,5 square millimeters copper wire (the one used in 16 A plugs). I'll roll it around some sort of wooden rack so that it'll stay fresh, not changing the resistance, which grows the hotter the metal gets, screwing up the counts which consider the resistivity of copper room-temperature (0.018 Ohm x mmq). Then I'll fit a few clamps at different lenghts on the wire, e.g. at 28 meters for 20 amps, etc.

Hope I'm not being delirious
Please let me know what you think of my reasoning.

Thanks again

[KCV6]

Hi Marco,

You are correct, ohms law (E=IxR, where E = voltage, I = current and R = resistance) determines what happens with current voltage and resistance. If you have a fixed voltage, to obtain a variable current flowing through the tank you need to vary the resistance. The way ohms law works is to imagine a triangle with E on the top and I R on the bottom. Therefore if you want to know the resistance required at a known fixed voltage and a known current the formula would be E/I = R (Voltage divided by Current = Resistance.

So ohms law is:

E = I multiplied by R.
I = E divided by R.
R = E divided by I.

Where it gets tricky is power, you need to make sure the resistance wires you have can cope with the power. In the above example the resistor setup must be able to disipate 12 watts.

Take a look here, there are online calculators for working out everything ohms law.

Ohm's Law Calculations With Power

Now back to the voltage versus current calculations for electroplating. With no additional resistance in a plating setup (just a good power supply and wires) and good plating solutions with the correct amount of brighteners and wetters all plating can be achieved by aplying a voltage. I never calculate how many square inches any of my items are. I always set voltage to what I know is the correct range for my tanks. For nickel and nickel cobalt it is 3Vdc, for zinc it is 0.8Vdc. The only time this differs is if I am plating a very small piece, I then use 2Vdc for nickel and 0.5Vdc. I have plated a single small screw with less than 1 square inch of surface area at over 0.5A and it came out fine because my solution was correct.

The majority of commercial nickel plating solutions have an operating window of between 3Vdc and 6Vdc, most commercial chloride zinc setups operate between 0.5Vdc and 1.5Vdc. I can take a bracket of say 50 square inches surface area and with absolute confidence apply 3Vdc to my NiCo (copy chrome) setup and leave it for 15 minutes and I will have a nice shiny defect free nickel cobalt plated part because I know that my power supply will provide the current that item requires automatically due to ohms law, provided i have placed the part equally spaced between the anodes in my tank.

I know this is all a lot to take in and I am rambling a bit but I have seen so many posts on here where people (including myself in the early days) had failures with copy chrome and zinc. Items rusting or tarnishing within days of being plated, dull patch plate, black streaks etc. This was because our solutions were wrong and we made them wrong. We didn't take the time to first plate small test pieces. The smartest thing I ever did was to take the copy chrome solution I had got completely wrong over about a month of mucking around by adding acid, brightener, more acid, more brightener and putting the whole lot through a charcoal filter and baselining it. I then added what was the correct amount of brightener and hey presto everything started to work fine. I now track how many amps I plate per hour and add brightener at the correct rate. The only time my tanks ever get it wrong is when I have a failure in plating due to bad prep by me of aluminium or zinc diecats parts and my tank gets contaminated.

My advice is to get a benchtop supply that displays current and has variable voltage, or get a variable current supply. This will allow you full flexibility to do everything you need to do. It is money well spent.

Cheers

Mark