Copper plating white metal parts

The stack and smokebox as they come out of the box

Dutch steam locomotives were fitted with a copper crown on the stack before WWII. The stack supplied by DJH ModelLoco with its NS7000 kit is just an ordinary white metal one. I've seen several completed loco's on layouts with a stack rim colored with copper paint. A fast and easy way to suggest a copper crown but not even close to real copper.

It took me some time to figure out how to make a copper crown. Okay, I could turn an entire new stack from brass, but I don't have a lathe. And I did put honor in solving the problem on my own. Before long I got the idea to copper plate the stack. I am a chemist by education, long, long ago. I knew I could use electrolysis to add a thin layer of copper to the stack. Remember electrolysis? Second grade chemistry? Periodic table of the elements? I will save you the technical details. It comes down to this. Copper in a watery solution tends to deposit on white metal hanging in that solution. You'll need a little DC to stimulate this process, the solid copper on the positive pole will solve in the water, will cross the watery solution and settle on the white metal on the negative pole and will form a thin layer of copper there.
So far the theory. It caused me some headaches, with a lot of "yeah sure, I used to know this" moments, to put this theory to practice. But I managed. Follow me, please, and I'll show you around in René's wonderful world of chemistry for dummies.

The first exercise for the beginner chemist is the making of a useable copper solution. I've been browsing the internet for suitable copper salts, but they are hard to get for private individuals, not so much from their nature as from their quantity, what on earth would I need 5 kg copper sulphate for? Moreover a copper solution is easily home made, so why bother? An old DC transformer, copper wire and a key ring will suffice. Attach

the key ring to the minus pole, the copper wire to the plus pole, hang them in a glass and add distilled water. Add a little household acetic acid (usually 8% solution) for electric conductivity. Open the transformer to about 5V and wait for an hour. The solution will have turned blue: solved copper in the water!!

Tips

• Clean the glass thoroughly with distilled water before use. Any soap or contamination could spell trouble.
• I used kitchen salt for conductivity at first but the solution became troubled. Copper chloride is insoluble in water and your so much desired copper solution will not form. Copper acetate though does solve in water and that is why I used acetic acid.
• Don’t swap the plus and the minus when using a model railroad transformer. It won't work. If you don't know what plus or minus is, just try. 50% chance!! If the solution does not turn blue, repole the transformer, make a new solution and try again. Make a note to remember for next time.
• Copper salts are mildly poisonous. They won't hurt you when handling normally, but see to it that none of your household takes it ad fundum.
• Theoretically copper salts are environmentally hazardous. So if you play by the book, don't waste it through the sink, but fill it in a waste bottle and turn it in as chemical waste.

Having a clear blue solution, you can turn your attention to your work piece. It is of importance to prepare your work pieces well.

1. Polish them so the surface is as smooth as possible. The smoother the surface the better your copper plating will look in the end. If you polish after copper plating than you'll will scrub your beautiful but oh so thin layer of copper into oblivion.
2. Clean them of any polishing or whatever dirt there may be
3. Degrease them thoroughly
   
   

Attach your work piece to the minus pole, hang the copper wire and the work piece in the copper solution and put some 5 Volts on it. It need'nt be exactly that but too much voltage will overdo the process and the copper layer will not attach to the white metal.

Small bubbles will form on the surface of the white metal. Tap the work piece carefully and regularly to remove them so as not to obstruct the formation of the copper layer. Your work piece will turn black. Rest assured! That is copper in crystalline form depositing on the surface. When it all turns black, take your work piece out and wipe it off with a piece kitchen paper soaked in the afore mentioned household acetic acid. Avoid touching the work piece with your skin so as not to regrease the surface. Hang your work piece and wait. Repeat this procedure again and again and already after a few times you will see a faint translucent copper shine appear. Repeat the procedure until you are satisfied with a convincing copper color.

Final tips
If you interrupt the process, don't leave your work piece in the solution. Take it out and dry it. The solution is chemical by nature. It will corrode the white metal and cause dents to form. If you observe the photos closely you can establish that if found this advice by own experience. This impairs my statement that copper plating is a safe method to upgrade your white metal parts. Well, to provide full proof I also treated the left over smokebox. The result are shown hereunder.

Principally there are no objections why you shouldn't copper plate an entire model but polishing it up might just be too much a tedious job. Have fun copper plating parts of your kit and please do inform me about results you achieve!!