Voltage for electroplating

[hannemcnc]

Hi everyone,
I am looking at building my own power supply and need to know if there is an optimum voltage for plating.

Will be plating copper, nickel, zinc and real chrome.

I have seen the voltage being used either 6 volts or 12 volts, usually from car batteries.

If it makes no difference 6 volts would be better as this gives double the amps if the same power supply is configured for 12 volts.

Can someone shed some light as to the theory behind the correct voltage required??


Thanks

[KCV6]

The voltages vary depending on the process and also surface area being plated. It is actually the current that is critical.

My advice... Buy a variable current/variable voltage power supply. They are not that expensive compared to the grief you will suffer not being able to easily vary both voltage and current. I got a 30Vdc 60 amp one from a HAM Radio supplier here in aus for $240 Aus dollars. There are heaps on ebay. Mine says it is only adjustable between 1Vdc and 30Vdc, hence the low price. I spoke to the guy who sells them and he said they actually go down to 0.8Vdc which means it is fine for all tank electroplating. 1Vdc can be a bit high for zinc. 0.8 is fine.

Alternately buy one of the ones Caswell sells.

Cheers

Mark

[hannemcnc]

Hmmm,
I do understand that the Amperage is critical but did not think that the voltage was as important.

How is it that plating can be done at 12 volts (from what I can glean from this forum?)

Is it not too high as you indicate that at times 1V can be too high.

Really trying to get a grip on the process and am not questioning your knowledge at all here.

True that if voltage must be variable as well then it certainly would be easier to get a dual variable unit.

Building a variable supply on either volts or amps is not all that difficult but not sure how to build a dual variable one. Have not looked into that yet.

It appears that power supplies are fairly expensive for what you get, the components are not that pricey and there are also many places to get units that will supply high amperes at low(ish) voltages.

Microwave ovens and old welders quickly come to mind. But like you say if you do indeed require voltage adjustment then that might change things.

Part of where I am heading with all this is to try and do real chrome but do understand that very high amps are needed, 1A per sq 1" that is a lot indeed.
But not impossible to build a supply.

Anyone feel free to add more or shoot me down.

Michael

[KCV6]

They build a 12V supply by running battery 12Vdc through loads such as automotive 12V lamps to drop the voltage and control the current. Chuck a series of varying 12V lamps in paralell and pick off points between to get different current ratings. Personally my workshop is well enough lit. Another trick is to run it through strings of nickel wire... poor mans rheostat.

Depending what chemicals you get/use for your plating baths determines how critical ASI calcs or just running a known voltage is. Caswell products work well but some have narrow operating windows on current per square inch and temperature. My copy chrome setup only works if the temp is witin 10 degrees c of what it should be and damn near spot on with the current per square inch of material plated.

Correct Chrome requires a good high current rectifier.

The expense of getting a real power supply is nothing compared to the sheer frustration of not having that level of control. It's like trying to paint a masterpiece with mud.. it will work but mud is mud. Trust me I am speaking from experience here. LOL

Cheers

Mark

[seanc]

Michael:

I believe most of the plating chemistries are current dependent. There may be some chemistries that are voltage dependent, but I'm not familiar with them.

Building a variable supply on either volts or amps is not all that difficult but not sure how to build a dual variable one. Have not looked into that yet.

It's simple really:

• If the plating chemistry is current dependent, you want one w/ controllable current.
• If the plating chemistry is voltage dependent, you want one w/ controllable voltage.
• If you expect to do both types of plating, you want both controllable.

You CANNOT control both simultaneously. You get to pick control over one or the other, voltage or current. Mother nature picks the remaining one.

Determine the maximum current & voltage you'll ever need, for the largest parts you plan to plate, with the most aggressive chemistry you plan to use. Build a supply that can deliver both maximums, and put variable control on the appropriate one (usually current control).

It's just not quite black & white. eg. 12v is inadequate for LCD anodizing, but OTOH, it's overkill for zinc plating. I've never had zinc go above 3v. (with very small parts, < .5v)

I know chrome requires very high current densities, so will probably be your worst case. But someone familiar w/chrome would have to say what max voltages to expect.

Sean

[KCV6]

Clarification:

It is all current driven, however so long as your supply meters both voltage and current you can set the voltage to a typical level for your setup and fine tune to get the desired current (read the I meter) for the load in the tank. If you have good plating solutions with wide operating windows you will never have a problem.

There are other considerations.... electro stripping etc. if you get a good variable supply you can use it to do everything you need to do all at the twist of a couple of dials.

Cheers

[hannemcnc]

Lads,
Thanks for the great replies,(Mark to the other query as well)

I popped in to see Paul tonight who is the Aus distributor for Caswell and picked up a copy of the handbook.

Will give that a good going over and will no doubt have more questions.

Cheers Michael