Monday, January 10, 2011

Galvanic Copper Plating

Hello again; long time no blog. I'm back in the workshop again, finally, and very excited about my current project. It's more quill pens, but they are very nice and different from what I had been making. I'm experimenting with some new materials, including shafts made of metal tubing. Some of which are being painted, and some I am going to try copper plating. This post is less about the pens (more on them later) and more about the copper plating process.

Some of you may remember my first attempt at using electrolytic (galvanic) etching. If not please check it out. Also it is worth checking out the reference sites I linked to in that post, especially of you are planing on doing any etching or plating yourself. Last time I was focused on etching. This time I am more interested in plating. The process is exactly the same, but with the polarity reversed.

I'm going to start with the raw metal tubing. What I'm using is 1/4 inch galvanized automotive break line. You can get it at any automotive parts store. I got a 60" long line for about $7. Both ends are flared, so if you don't want that, you will have to cut the flare off. I did. Then I cut a section to the desired length (5.25") with a tubing cutter. Tubing cutters can also be found in an automotive or hardware store. Mine cost less than $10. They are used for cutting any kind of metal tubing, but especially copper plumbing pipe.

Speaking of copper plumbing pipe, that's what I'm going to be using for both my anode and my vessel. I took a short piece of used copper pipe, I think it was 3/4" pipe that happened to be about 9" long, and cleaned it out real well with some muriatic acid (HCL). I was more interested in cleaning the interior than the exterior since that is the side that will be reacting during the plating process. I then stoppered up one end with a cork. This pipe will be filled with my electrolytic solution (copper sulfate) and will, again, serve as both the reaction vessel and the anode (I'm pretty sure I'm using the word anode correctly in this context, but please don't beat me up if I am not). Another advantage to using a copper pipe like this, is that all the surfaces to be plated are roughly equidistant from the anode and copper source material, which should ensure an even plating. If I were to use a copper plate anode on one side of a tank and the tube to be plated on the other, such as with my rig from my previous experiment, the copper would tend to deposit mainly on the side facing the anode.

I want to make sure that the piece of tubing is coated evenly and with no blemishes, so I will solder on a small metal tab for the alligator clip to attach. In my first attempt I used a 1" steel brad, but in this pic, I am using a "T" pin. I placed the end of the pin inside the tubing along with a small piece of solder (after coating the pin with flux). I used a neodymium magnet along the outside of the tubing to help hold them in place while I heated the pin with a small butane torch to melt the solder. I also ran some 1000 grit sand paper over the outer surface of the tubing to make sure it was nice and smooth for plating, though that probably wasn't strictly necessary.

I wanted to make sure that the copper pipe stayed perfectly upright during the process, so I used some newspaper as wadding and wedged it into the mouth of a glass jar I had handy. The jar will also serve to catch any leaks in case my corked end is not perfectly sealed (it isn't). I wrapped some thin galvanized jewelry wire around the outside of the pipe just to give me a convenient place to attach the alligator clip.

The metal tube I am plating will sit nested inside the copper pipe. In case you were wondering from the previous picture, that is a bamboo skewer stuck in the end of the tubing, so that it sits at the right height in the pipe. It is important that the tubing not be allowed to touch the side walls of the pipe, or it will complete the electrical circuit and nothing will happen.
Then the pipe is filled with the electrolytic solution, which in this case is copper sulfate. As in my previous experiment, I used a commercial septic cleaner called "Root Gone", which comes in a crystal form, that I added to water to the saturation point. I made sure that the water level was above the top of the tubing. As the cork leaks a bit, I will have to top it off periodically.

Using test leads with alligator clips on the ends, I attached the positive terminal of a generic 9V battery to the copper pipe, and the negative terminal to the metal tube (actually, to the T pin). In my previous experiments, using 12V at high amperage for short times was way too much current. It ate the anode very quickly and although it did deposit material on the cathode, that material did not bond and was easily wiped off. My previous experiments of using 1.5V at low amperage worked better, but very slowly. I did, however, leave it on for too long (14 hours) and it, again, ate through my anode. I was looking for some middle ground. I didn't have a 6V battery, so I thought I would try a used 9V that was still good, but kind of weak. I wanted the process to go fast enough that it didn't take all night, but slow enough that the copper being deposited would bond properly to the metal tubing.

I left it set up for about an hour and then checked it. SUCCESS! I had a nice even (if not a little thin) copper coating that was well bonded to the tubing. I wanted a little thicker coating, so I wiped it down and put it back in for another hour. Something worth noting, is that the finished product does not come out the nice warm orange-copper color we are used to seeing on pipes and wiring. It comes out a very bright garish, almost pinkish copper color, like a mint fresh penny. I'm sure a few days in the open air will tone it down and warm up the color (I hope).

On a side note, my used 9V battery was good for about two and a half plating sessions (total of 5 hours) before it had to be replaced. One problem I keep having is, I can never seem to remember which way to connect the battery. I have to keep looking it up. So this time I wrote myself a little note to keep with my gear. Material is REMOVED FROM THE POSITIVE terminal, and DEPOSITED ON THE NEGATIVE terminal. Write that down, kids.

UPDATE: Although the first two tubes I plated with this rig went off without a hitch, good coverage, no  problems. The third and fourth tubes were both problematic. The third one was the one where I switched batteries between the first and second hours, and its finish came out dark in some areas. It plated evenly, but it didn't look nice. The fourth was just a mess.The copper only stuck in patches, and covered less than half of the tube. I tried all sorts of alterations to the power supply to solve the problem. I switched out the battery again; I tried using a "wall wart" transformer (5V 2A and another that was 12V 800mA); I tried using a C cell battery. I got plenty of copper built up, but nothing would stick, and I even noticed some degradation of the tube wall thickness on just one end that sort of puzzles me. And I think I burnt out both of the wall warts I used. I guess my apparatus still needs some work. I will have to go online and see if I can find out what the optimal voltage and amperage would be. If anyone else has any idea what went wrong, please leave a comment.


  1. Informative and educational blog, Thanks for showing this.

    1. This is one technology that I would love to be able to use for myself. It’s definitely a cut above the rest and I can’t wait until my provider has it. Your insight was what I needed. Thanks