Copy Cad Plating - Keep getting dull finish

[dmcclain]

I am new to plating and I have the Copy Cad system. Each time I plate a part, I get the dull grey finish. I added the brightener to the solution but I get the same results. I have tried different amperages per square inch but the results are pretty much the same. What I am hoping for is to get the silver cad look on my parts like nuts and bolts and hinges and the bright and shiny zinc finish like would be on an automotive relay can etc. I have a 1.2 volt nicad battery setup using a rectifier to adjust the amperage. I use a digital ammeter to make sure I keep the amps to the recommended .25 milliamps per square inch. Any help or suggestions would be welcomed.

[seanc]

dmcclain:

I keep the amps to the recommended .25 milliamps per square inch

That's not near enough. Try for 80-100 mA/sq-in.

I struggled thru the same problems. See my test results, go to the bottom of the page to see the "brightened" parts, which really show the best results:

http://www.hogheaven.com/hobby/plating/zinc/tests/cctest1.html

I have a 1.2 volt nicad battery setup

NiCd batteries don't have much current capacity, so depending on what size battery you're using (AA, C, D?), it may not be able to handle larger parts at 100mA/sq-in.

using a rectifier to adjust the amperage

Can you elaborate what you're using?.

A basic rectifier converts AC to DC, but your battery is already DC, so it's not needed. If you're referring to some sort of constant current control, that's a good thing, but you'll probably need more source voltage to begin with. Current limiters usually incur their own voltage drop, usu. between 0.5-1.25 volts, so your 1.2v battery isn't enough.

What voltage are you seeing across the anode/cathode?

FWIW, I stopped using unregulated power sources, it's just too hard to "dial-in" just the right amount of current. It requires juggling 3 different parameters:

1) Part size (sq-in). Larger parts draw more current, so you'll have to readjust current limit for different sized parts.
2) Anode-Cathode spacing. Less distance between anode and parts draws more current
3) electrolyte temperature. Higher temperature increases electrolyte conductivity so it draws more current.

For these reasons, I've switched to a constant current power supply, I plate at 90-100 mA/sq-in, and everything works great now.

Sean

[dmcclain]

Thanks for the help. Acutally, I am using a potentiometer (not a rectifier)to control the current and my battery pack is made up of 10 AA nicads that have plenty of power. I also tried another set of nicads that had 3.7 volts but even that is too little according to your setup. The bottom of my anodes are getting dark and burnt looking so I thought this was an indication of too much power. I have been heating the solution to the recommended 110 degrees but your setup was at 65 degrees.

I have a glass bead blaster which I have been using but I haven't been using an acid pickle because I didn't think I needed to.

I'll give your method a try. Thanks again.

[seanc]

I am using a potentiometer (not a rectifier)to control the current and my battery pack is made up of 10 AA nicads that have plenty of power

10 AA nicads are more than enough current. Depending on the capacity of each battery, this should be somewhere in the range of 4-6 amp hours. You'll get some voltage drop across the potentiometer, but how much depends on how many ohms it's actually dialed in at.

tried another set of nicads that had 3.7 volts but even that is too little according to your setup

This depends on the potentiometer setting. If it's dialed to a fairly low resistance, it's plenty of voltage. Actual plating voltage across the anode/cathode is fairly low. You'll typically only get 0.5v to 1.2v, depending on the total size of the parts.

However, if your potentiometer setting is high, you'll be burning up too much power w/in the pot, it will incur a high voltage drop, so voltage at the anode/cathode might be low.

Don't measure voltage at the batteries. Measure voltage at the tank, across the anode/cathode. If it's less than 0.4v, then you're losing too much across the potentiometer, and you'll nee to raise the battery pack voltage.

If you check the "Sitcky" thread: ATTENTION SUCCESSFUL PLATERS - YOUR DATA NEEDED, I've posted some of my actual plating data:

http://www.caswellplating.com/bbs/viewtopic.php?t=3243

I have been heating the solution to the recommended 110 degrees but your setup was at 65 degrees.

I've heard reference to this temperature before, but don't know where it comes from. My manual (ver. 5), says 60-90 degrees. When I was having my problems, on suggestion I tried 110º but that made things worse.

I haven't been using an acid pickle because I didn't think I needed to

If the parts are rust-free and really clean, you don't need it. The only time I use it is if there's going to be any delay between the degrease/clean step, and putting the part in the plating tank. eg, if you take a parts out of the SP (or whatever you use) degreaser, rinse it, and leave it set for a few minutes, it will form surface rust. So if I have a lot of small parts that I want plate at once, I drop each one in a 5% muriatic pickle after degreasing, just to keep them from surface rusting. Then when they're ALL clean and ready to go, one more rinse to get the acid off, and into the plating tank.

A mild sulphuric acid dip (1-2%, for a few seconds) is useful AFTER the parts are plated. The zinc electrolyte is brown, and plated parts come out w/a brownish film. This brownish color will remain on bright plated parts. The sulphuric acid dip removes the brown film and leaves the part all silver/gray.

You can see examples of this in the photos I've posted below. (check the "U-bolt" and "Large parts" sections). I used muriatic acid dips for these early plating runs, but am using sulphuric now. It comes out better.

http://www.hogheaven.com/hobby/plating/zinc/parts/index.html

Sean