ShawnD
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Copper plating isn't going too well
I've tried to put copper onto a piece of iron several times, and nothing seems to work.
Solution Prep 1
I made the copper solution by cutting small pieces of copper wire into a glass jar, then adding bleach (sodium hypochlorite), then adding hydrochloric
acid. Hypochlorous acid is a strong oxidizer, so it oxidizes the copper chunks to make a nice dark blue solution. The solution has lots of solid
copper, so I know the hypochlorite is all gone when the copper stops dissolving.
Solution Prep 2
Fill a glass jar with water and some ammonia. Hook some copper wire to the positive terminal on a car battery and put the copper wire in the solution.
Hook any kind of wire to the negative terminal on the car battery put the wire in solution. Since copper hydroxide is insoluble, copper ions made from
the copper wire turn into copper hydroxide instead of being plated on the other wire. When enough copper hydroxide is collected, the electrolysis is
stopped, and hydrochloric acid is added to turn the copper hydroxide into copper 2+ ions. The solution is dark blue.
Plating Method 1
Just put the iron in the copper solution. Since copper is a strong oxidizer in its ionic form, it will spontaneously put itself in place of iron.
Result: The iron bar is destroyed, and copper just forms a thick mess around the iron bar. The copper mess looks like of like algae growing on wood .
Plating Method 2
Hook the iron bar to the negative terminal on a group of AA batteries in parallel then put the bar in the copper solution. Hook copper wire to the
positive terminal on a group of AA batteries in parallel then put the wire in the copper solution. It's basically just a normal electrolysis.
Voltage is only 1.5V, so reaction craziness in the solution should be kept to a minimum (no hydrogen, chlorine, or oxygen gas forming). AA batteries
don't put out a lot of current, so it certainly isn't plating too quickly.
Result: Same thing as just putting the iron bar in copper solution.
Here is a picture of the failed electrolysis attempt.
Notice all the fluffy copper at the bottom of the jar? That's what falls off the iron when I shake the jar.
What am I doing wrong?
[Edited on 21-3-2005 by ShawnD]
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Marvin
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Few suggestions with a vaguely southpark theme.
Iron is bad, you dont want to be plating onto anything thats trying to dissolve.
Chloride and ammonia are bad, they stabilise the Cu(I) oxidation state. I suggest copper sulphate, if you cant find it you can dissolve copper in a
mixture of dilute sulphuric acid and hydrogen peroxide.
Dilute solutions are bad, they result in dendrite formation, or powdery copper in extreme cases. You want the copper sulphate solution neerly
saturated I would think.
Thats all I remeber off the top of my head. If I find something specific for good plating I'll post or add.
Mmmkay?
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JohnWW
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Probably the only sure way you might be able to do it, without iron going into solution, would be "hot dip" plating on iron
("pickled" briefly with acid first to remove any oxide) with molten copper, which has a much lower melting point.
However, I have seen aluminium successfully plated with copper, so there should be an electrolytic method of plating iron with it, with the iron
attached to the positive terminal (cathode), and dipped into a copper salt solution (neutral to slightly acid) with an anode of something inert like
carbon.
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12AX7
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Of course, that needs a generous temperature.
If you must go that route, the technique is furnace brazing, and uses borax for flux (since iron and copper rapidly oxidize at that temp). Copper
will flow very well over the surface.
Tim
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Twospoons
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Plating on a thin layer of nickel first may help with adhesion of the copper.
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Dave Angel
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Ever useful yahoo groups
Hello all,
I have also found electroplating to be very troublesome in the past. It seems to be something of a difficult technique to get right, and the
professionals frown upon us mere mortals dabbling with it; something to do with dangerous chemicals etc. etc.
Anyway, I came across a yahoo group some time ago which doesn't mind you being a hobbyist and has some useful files and guides available for download.
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ShawnD
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Thanks for all the help guys. I can tell I'm going to love this forum. 
[Edited on 22-3-2005 by ShawnD]
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hodges
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If you put a more active metal in a solution with a less active ion, the metal will eventually dissolve. What is produced is the metal that was in
solution, but it is not in the form of plating - it is in the form of scales. For example a popular chemistry demo is to suspend a copper wire in
silver nitrate solution. Silver does form on the copper, but the copper does not get "plated" with silver. Instead the silver forms and
falls down as a powder, similar to the way it looks like copper powder fell from your iron.
Getting a plating to stick is an art, as you have heard. For one thing the metal must be very clean. This means you should wash your iron in
something that will remove all the grease - perhaps sodium hydroxide. Then you should sand and polish the metal.
Try plating some copper on a nickel or quarter coin, using a battery. This should work and should help increase your confidence. Again, don't
expect a perfect coating, but you should definitely see a coat of copper.
You need to try more voltage. 1.5 volts may not be enough. Try a 6V lantern battery; these have a lot more current capacity than a penlite cell.
You might also try a "wall wart" DC power supply for a radio or something.
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