Zinc plating issues

[kenrinc]

So I've setup my tanks after a couple years. Filtered the crystals and everything looks good. Setup my power supply (variable DC bench supply). Hook + to zinc anode and - to the part and I cannot get the unit to dump current. I assume constant current is the mode I want to be in but whenever I turn up the current knob it will only move up to maybe .04 to .06 amp, that's it. I ran into this once before with these DC bench supplies but I can't remember what the issues was. Does anybody have any suggestions?

Thanks

Ken

[KCV6]

Hey Ken,

Not sure which power supply you have, but to use constant current, you have to make sure the voltage is also set high enough. try setting the voltage to 1Vdc and then set the current to the value you want. With zinc, the voltage should be between 0.5 and 1Vdc for the correct amount of current to flow through a zinc setup.

Cheers

Mark

[kenrinc]

Thanks Mark. Yeah I keep forgeting the CC thing. Some meters have a procedure you have to go through others are auto setting. I believe mine is auto setting so you set the voltage first then hook everything up and set your current. My voltage is already set to 10v and whenver I turn up the amp knob I get nothing. Fluctuates around .06amp but won't dump. I'm unsure if it's the plating tank makeup or if it's wiring.

Ken-

[seanc]

Ken:

My voltage is already set to 10v and whenver I turn up the amp knob I get nothing. Fluctuates around .06amp but won't dump. I'm unsure if it's the plating tank makeup or if it's wiring.

What power supply are you using?

I'm gonna guess it's one of the low-cost power supplies. If that's the case, many of those power supplies can't handle low resistance loads, and go into protection mode, thinking it's got a short circuit.

You many have to add a low value resistor in series to bring the load resistance up to the point where it will operate.

Check these prior posts:

• MY Power Supply Has Me Confused - can't control Current
• 3 amp power supply

Sean

[kenrinc]

One of those mastec style. I do remember the resistor trick. Not sure why it's so inconsistant though because I never had to do this when I first got it. Anyway, I got a 20w 8 ohm resistor and sure enough that fixes the issue although I'll need hefty unit to do bigger pieces.

Thanks

Ken

[kenrinc]

OK, so it plates, sort of... all I get is dull grey plate. Handbook says it's too much power but it's not. Calculated .9 amp so I tried .6, .9, and 1.2 and get the same dull grey plate. Tried at the extremes of those 3 and still same thing. Tried plating some copper for 30min to get things going and just get the same. What gives? This actually happens quite a lot for me. After a few days, I come back and start plating again and things work fine then all of sudden this will start happening again.

Ken-

[seanc]

Ken:

I don't quite know what to make of the plating inconsistency. A couple of thoughts though.

8 ohms is way more than you need, you might try something in the 1 ohm range, for a couple of reasons:

• the lower the resistance, the lower the needed wattage
• too much voltage drop: 8 ohms will burn @ 90% of the available voltage. At higher currents, there may not be enough voltage left to provide the needed amps.

eg, at 2 amps, that resistor alone will drop 16 volts, @ 32 watts. A 1 ohm resistor would only drop 2 volts @ 4 watts.

How many amps/volts is your supply rated for?

The fact you can leave it for a few days, come back & have it plate good for a while before going south, sounds suspiciously like a power supply problem.

Any way you can monitor voltage & current w/separate meters?

Sean

[kenrinc]

Sean,

Your dead on man. That friggin resistor was going to light up and fly away ... I could dump about 2.5amp before I started to hear the resistor cracking. The PS is a 30v/10amp. I'll see if I can find a 1ohm unit today but I'll need to source another unit soon. It's weird, I suspect power supply too; I don't think there is anything wrong, just the weirdness brought on by going through the 8ohm resistor. Little stuff takes a lot of power just to plate. I will calculate the surface area of a part (say it's 8 sq in) and I typically go with .08 amp per sq in for plating power. I calculate roughly 650ma to plate but I end up having to use double that to actually get a good plate. It's weird.

Ken-

[seanc]

Ken:

That friggin resistor was going to light up and fly away

They make darn good heating elements, eh?

w/30v available though, that .9 amp run should have plated fine w/the 8-ohm resistor. Shouldn't have needed more than 8 volts.

At higher currents, the resistor may not be necessary. Just depends on your particular power supply. You'd have to experiment with it to find the protection cut-off load.

But if you ever wanted to use a resistor at the full 10 amps, then 2+ ohms is about the largest value. But that would have to be @400 watts! You won't find one like that at Radio Shack! A 1-0hm would need to be 100 watts, .5-ohm @ 50 watts. These sizes are much easier to find.

I will calculate the surface area of a part (say it's 8 sq in) and I typically go with .08 amp per sq in for plating power. I calculate roughly 650ma to plate but I end up having to use double that to actually get a good plate. It's weird.

That's good for the old formula electrolyte, but not enough for the new formula. The new would require @1.1 amps. Are you using the new or old formula electrolyte?

Sean