There seems to be alot of leg work in plating PLEEASE HELP

[wop1969]

gsw3

The real question is can you plate aluminum?
If so what kind of problems have you had?
I plate aluminum but 40% of the time if gives me a run for my money.
I win eventually but I had allot of problems at the start of my plating experience and no one seemed to be able to answer any of my post
So now that I figured it out I am just wondering if anyone else plates aluminium?

[gsw3]

"The real question is can you plate aluminum?"

I have not done much aluminum, mostly steel and brass.

I use a modified version of what is in Caswell's manual (not using the zincate method).
It is a ton of steps to do it that way.

I will have to get some zincate and try plating with it so I can get some first hand experience (and maybe help you guys and gals out).


George W.

[Fibergeek]

I don't know as much as you guys know about electroplating; but I am an electrical engineer, so I do know a thing or two about electricity.

Electroplating is strictly governed by Faraday's Law, which explicitly states that current (amps) does the plating, not voltage. Michael Farady figured this out 200 years ago, its just as true today as it was then, and its not going to change.
Faraday's Law also governs anodizing, which I do know a little about. After cooking up LCD, I set about on the anodizing forum to pry people away from this "voltage anodizing" idea, that forum was a disaster, nothing was working. I know firsthand how attractive "voltage" is to those who don't understand how electricity works, but this "idea" was the root cause of the majority of the anodizing problems they were having. A year later its pretty quiet over there. Its common now for 1st. time anodizers to get very good results on their 1st. attempt. This has nothing to do with LCD, its all about not attempting to violate a Physical Law. It that were possible the Law would not be a Law, it would be a theory. For practical plating purposes, all you need to remember it that current (amps) does the plating.

There is another Physical Law, Ohm's Law, which is also operating in anodizing and electroplating. Everyone has heard of it; V=IxR, but few understand how to apply it. If you do, electricity is simple, understandable, and entirely predictable. You guys need to get this, like the guys on the anodizing forum did, it will make your plating endeavors so much easier.

The third entity in Ohm's Law, Resistance (R) is the one everyone wants to ignore. But without it, you will never understand how voltage relates to current, and the trouble starts. I can see why people try to ignore resistance; voltage and current are easy to measure, you even have meters on you PS that show both. When you're dealing with a plating tank resistance is not so simple, alot of things effect it. Resistance here is a combination of:

The surface areas of the anode and cathode.
The resistance of the electrolyte (the big one in plating).
The temperature of the electrolyte.
The material you are plating onto.
The distance and geometry between anode and cathode.
The size of the tank (both its volume and shape).
Plating time.
How good (or bad) your wiring is.

Before this scares anyone off, you only need to know the total resistance for most practical purposes. Since you can measure the voltage and current; the resistance is R=V/I. Simple arithmetic. In the same tank, with the same materials, the total resistance isn't going to change very much. You will be able to predict it by knowing the surface area of your work, the current you will need and be able to calculate the voltage you should expect, and not have to find out the hard way.

The link below is a pretty good technical explanation of electroplating if you as so inclined.

http://electrochem.cwru.edu/ed/encyc...lectroplat.htm

OK, so what does this have to do with this thread?

The trap in expressing electroplating current densities as voltages is that it is only valid if the total resistance remains the same. This would require everyone to be plating identical work in identical tanks, fat chance. The voltage that produced a certain current density in one tank can be wildly wrong in another.

Below I have paraphrased George's voltages into their corresponding current densities, easy to do with Ohm's Law. For George, and in George's tank, if George wants to relate current density in terms of voltage, that's fine and he should feel free. You can do this too once you have determined the correct relationship in your tank, but not before.

Acid Copper: 1.50V @ 85ma. per square inch. 17.6 Ohms per sq. in.
Bright Nickel : 2.25V @ 85ma. per square inch. 26.5 Ohms per sq. in.

I always ramp up the voltage during the first few minutes of plating to insure the metal plates quickly verse oxidizing in the solution.
(really important when nickel striking steel parts) I increase the current density for the first few minutes.

Nickel:
1st min. 3.0V 113 mA/sq.in.
2nd min. 2.75V 104mA/sq/in.
3rd min. 2.50V 94mA/sq.in.
Then at the 4th min. mark it gets set at 2.25V 85mA/sq.in.

Acid Copper:
1st min. 2.0V 114mA/sq.in.
2nd min. 1.75V 99mA/sq.in.
Then at the 3 min. mark it gets set at 1.5V 85mA/sq.in.

I have a "Lab" type power supply (0-18Vdc, 0-10A) and using the settings above always gives me perfect results. So long as your total resistance doesn't change.


OK, now this ought to shake everyone up.

All this worry about the "exact" amps per square inch.
I set my supply to the voltages listed above and let the part draw whatever it wants. I use no direct control of the plating current.
Always seems to draw right at 85ma. per square inch. The area of my parts is always the same or close enough.
I have never set the current limit on the supply to match the part size, ever! I have never set the PS to actually run in Constant Current mode, so I don't know what a convenience this is.

There are power supply issues going on in this forum too. These have nothing to do with plating, and are design issues in the power supplies. I touched on a few of them in another thread in this forum started by Gabourie. More on this later if anyone's interested.

[Gabourie]

Fibergeek!
I am interested as I would like to be able to optimize the plating tanks I have by using any tips I can from others who are doing it and having consistent success. I am getting closer to getting consistent results but I am now getting confused by the more I read. So many ideas. I find myself saying ok, what should I try this time. I want to know that when I plate something it will work. And I will get the desired results. So when it comes to answering your question about being interested, YES . I am still having power supply issues. But I have learnt a lot with your help as well as others. I can get by, but the confidence is shaky. The big one is with the resistor, to start the power supply I am not sure how that can or will effect the current. If I use constant voltage mode or constant current mode what the meter says is not what the part "see's". I have also realized that alot of the problems I had were from the degreaser not rinsing off the polished parts . The mixing instructions I got made a double strength degreaser. So constant current or constant voltage?

[Fibergeek]

If you are operating in Constant Current mode, the resistor has no effect at all on the current, only the voltage. In CC, you set your plating current (amps) which in indicated on the ammeter, you do this with your resistor in place. After the PS is running, you can short out the resistor, you will notice that the current (amps) remains the same, but the voltage has changed (it went down a little). The plating tank saw the current that you set, the resistor made no difference at all to the plating. The current density did not change at all. This is how CC works.

Now say you set the PS up for Constant Voltage mode. If you do the same thing with the resistor as above, the voltage will stay the same, but the current changed. This means you changed your current density; not good, unless you have a plating reason to change the current density during the operation, like Gsw3. And if so, it would be much easier and more accurate to simply adjust the current in CC mode (with the current knob).