Some questions about copper plating

[Andy1845c]

I know this isn't an ideal place to ask this, but I know there are some folks here that might be able to give me some information.

I am fascenated with the metal copper. I have been saving scraps of copper wire for a while now, and what I would like to do is convert all the scraps into a block or lump of pure copper. Just as an art object/conversation peice.

I read somplace (can't find the link now) that pure copper does not cast well and is prone to cracking unless other metals are added to it.

I remember seeing on tv how pure copper for use in electrical wire is made using an electroplating process.

I found this website that shows an experiment with copper plating on a very small scale. **broken link removed**

Does anyone see any issues or have any comments on doing this on a slightly larger scale? I probably have a couple pounds of copper I would like to make into one lump. Are there any other chemicals I could substitute?

I'll leave it at that for now. I do have some more questions about the process, but i'll first see if anyone can advise me.

Many thanks!
Andy

 

[dknguyen]

Wouldn't copper plating oxidize really fast? Why would you plate anything with copper as the outer layer?

What would happen if you just tossed it all into a wood (or maybe another kind of slightly hotter) fire? Isn't that what they used to do?

 

[Krumlink]

It would have to be 1984F or some 1000 degrees Celsius.

You could make a ton of money at a metal reclamation center.

 

[Andy1845c]

Wouldn't copper plating oxidize really fast? Why would you plate anything with copper as the outer layer?

I'm not sure. Thats why i'm looking for opinions. I figure the lump of copper will tarnish no matter what method I use to make it, but maybe I could polish and clear coat it or somthing.

What would happen if you just tossed it all into a wood (or maybe another kind of slightly hotter) fire? Isn't that what they used to do?

I tried melting a small amount of wire with a cutting torch once. It didn't flow very well and ended up with alot of pocks and cracks in it.

I'm not sure exactly how early man made copper tools and such. I guess I'll google it. I know copper and tin are mixed to make bronze, and that I think is a bit easier to work with.

 

[Andy1845c]

It would have to be 1984F or some 1000 degrees Celsius.

You could make a ton of money at a metal reclamation center.

I think its feasable to melt copper in a wood fire, as early man did it. But I haven't tried it yet.

Yeah, I could scrap it, but wheres the adventure in that?

 

[dknguyen]

I'm not sure. Thats why i'm looking for opinions. I figure the lump of copper will tarnish no matter what method I use to make it, but maybe I could polish and clear coat it or somthing.

Acrylic conformal coating?

 

[3v0]

I think its feasable to melt copper in a wood fire, as early man did it. But I haven't tried it yet.

Yeah, I could scrap it, but wheres the adventure in that?

I would think if you check the web you will find info on building a home foundry for brass, bronze, and alu. A good place to start.

 

[BeeBop]

I think its feasable to melt copper in a wood fire, as early man did it. But I haven't tried it yet.

Yeah, I could scrap it, but wheres the adventure in that?

Yes; you need a bellows to deliver lots of oxygen. My grandfather had an old forge, which ran on coal. You had to turn a crank to pump the air into the base of the flame.

3V0 is correct, there are some home foundries on the WWW. I can't remember where, but I have seen them.

Of course, bronze is better for what you want...

 

[Andy1845c]

I would think if you check the web you will find info on building a home foundry for brass, bronze, and alu. A good place to start.

I have seen alot on the web for casting other metals, but I am under the impression copper is very difficult to cast. Here is the artical I couldn't find earlier - Copper and Copper Alloys Casting Problems It describes using crushed graphite to cover the melt and adding calcium boride or lithium. I don't really want to create an alloy. I don't know if thats what this would do, or if all the other stuff will end up as slag on top of the melt.

I guess I need to find a metallurgy forum. I've been looking but can't find one yet.

 

[3v0]

I have seen alot on the web for casting other metals, but I am under the impression copper is very difficult to cast. Here is the artical I couldn't find earlier - Copper and Copper Alloys Casting Problems It describes using crushed graphite to cover the melt and adding calcium boride or lithium. I don't really want to create an alloy. I don't know if thats what this would do, or if all the other stuff will end up as slag on top of the melt.

I guess I need to find a metallurgy forum. I've been looking but can't find one yet.

Look for a forum on home foundry work. The graphite is providing a barrier between the metal and the air. I think we used borax but maybe that was just for forge welding. Too long ago.

A home foundry for melting bronze is not difficult to make. Mostly a weed burner stuck into a ring of fire brick (tangent to the circle) with a graphite crucible to hold the metal. Slab of fire brick for the top. Forge bands of iron to reinforce and bond it all together with furnace cement. LOL actualy you can line a large tin can with high temp brick and use it for small pours.


Is there some good reason not to make an alloy ?

 

[quixotron]

yeah mix it with aluminum!

 

[HarveyH42]

Search backyard forge, should get tons of hits. Instructiables has several for aluminum, using coffee cans, soup cans, charcoal, and a hairdryer (forced air). I've done lead/tin pewter for years, and occasionally get an itch to try higher temp metals.

 

[monkeybiter]

i've seen copper 'bails' for 'simulating' through hole plating, i reckon you could probably make these yourself by plating thin strands of solder. could be a fun and relatively easy experiment.

 

[Glyph]

I've actually electroplated copper and created items on the miligram to multi-pound scale.

While its relatively easy to create a thin coating of copper onto other metals, the difficulties lie in getting the coating to be of the properties you want. Normally copper comes out as a matte salmon coating. While good for protection this looks terrible.

Special chemical additives like benzotriazole are added to the copper plating solution to change the deposition process and give you a mirror finish on the plated copper.

Things get tricky when you want to actually create objects, like a lump. This process is called electroforming and suffers from the problem that metals plated in this way don't assume an easily predicatable shape. This is because when the current is applied some areas are going to get a higher current density than others, this causes those spots to plate faster. Unfortunately, this process tends to occur with a positive feedback, the high density area grows in such a way as to incur an even higher relative density which in turn makes it grow even faster. In the end, you get a massive chunky deposit with feathered edges and "trees" growing accross its surface (you'll know what i mean when you see it....).

Concentrations of copper and acid is also important. Most copper plating is done with sulfuric acid and copper sulfate. high sulfuric acid and low copper sulfate tends to produce more even deposits, but is slower to plate. Reverse that ratio and the opposite occurs.

Alkaline copper baths work better, but are composed of very highly toxic chemicals.

additives added to the bath deplete after prolonged usage so you need to maintain those concentrations precisely. too little additives and the copper comes out crappy, too much and it looks like an alien copper fungus is growing on your stuff.

The amount of current is also an issue. Voltage is not what you need to control, its current. Too much current on too small an object will induce treeing and feathering. Too little current and the additives might not work since they need to "stick" to the surface based on the surface voltage level.

Filtration is a requirement when making larger pieces. if a speck of insulating dust hits your surface the deposit will form a pit. If a speck of conductive dust hits your surface the positive feedback i mentioned earlier will create a tree.

And even if you get the shiny mirror finish on copper it will quickly tarnish in air.

All of that being said.... There is nothing quite like the feeling of lifting out a beautiful mirror shiny object that you knew a few hours ago was a dull sand-blasted hunk of metal.

Copper is the easiest of the metals to plate and even a beginner can do a decent job.

Anything more specific you want to ask?

 

[Andy1845c]

Glyph, thanks for the awsome reply!!

I'm not too concerned about the shape of my copper "lump" when its done. I want it to be interesting to look at. Not a perfect cube or anything.

How do I figure out the right sulfuric acid and copper sulfate mixture? Trial and error? Is this mixed with water? Will the acid mixture last a while, or does it depleate and have to be changed though the process?

Do you have any suggestions on what a hobbiest like me could use for a power supply? I was thinking of an automotive battery charger, but that wouldn't allow me to control the current very much.

How is the filtration done? Is it sorta like a pool filter that is just circulating the solution though a filter?

What time frame am I looking at to take a couple pounds of scrap wire and make a couple pound lump? A week? a mouth? Way longer?

Sorry to bombard you with questions. I'm just glad to see somone here knows about this!

 

[Glyph]

Glyph, thanks for the awsome reply!!

I'm not too concerned about the shape of my copper "lump" when its done. I want it to be interesting to look at. Not a perfect cube or anything.

An lump of copper that looks like an alien lifeform might fit the bill

How do I figure out the right sulfuric acid and copper sulfate mixture? Trial and error? Is this mixed with water? Will the acid mixture last a while, or does it depleate and have to be changed though the process?

The mixtures are available online, high acid ratio solutions (also known as "high throw") tend to be around 180g of sulfuric acid and 60g of copper sulfate added to 1L of water. High copper solutions tend to be around 210g of copper sulfate and 20-30g of acid per 1L. These numbers though are not "sweet spots" and actual ratios can vary greatly. The additives you add tend to dictate the concentrations since the additives are chemicals and therefore require a certain chemical environment to function properly.

If you are using no additives then the process can be very forgiving and you can just dump in acid and copper any way you want and still get plating if you just adjust your current accordingly.

As for how long it lasts. Once again the additives play the key role, they are the ones that deplete and change the makeup of your bath as time progresses. some additives will breakdown even without usage and so your plating bath will have a limited shelf-life.

In the case of no additives, technically the bath should last forever. This is because unlike most other metals in plating, copper plates with 100% coulombic efficiency. Every atom of copper that plates into solution from the anode is equally accounted for by an atom copper plating out of solution at the cathode. So even if you pump a million pounds of copper through the solution, it should technically remain the exact same composition as when you started (acid does not get affected by plating, it just helps the movement of ions and conductivity). However, real copper is not 100% pure. There will always be tiny bits of iron or other metals that plate into solution, but will not plate out. Over time these build up and contaminate your bath. But this a minor issue if you maintain clean practices and filter your bath often. I was able to run my baths continously for several months and contamination never became an issue. Although i still recrystalized my bath after that time just because i like the mental feeling of knowing i've got pure materials.

Do you have any suggestions on what a hobbiest like me could use for a power supply? I was thinking of an automotive battery charger, but that wouldn't allow me to control the current very much.

Around these forums you will find designs for constant current power supplies, i suggest you start there.

Personally I built my own switch-mode constant current power supply.

I do know that most casual platers get away with simply getting a giant unregulated power supply (transformer, diode bridge and capacitors) and then adjust the output with a variac. They watch the current through a shunt resistor. This method has the problem that the current isn't stable and might change as the shape of your object changes during plating.

Others use giant high-wattage resistors to control the current.

How is the filtration done? Is it sorta like a pool filter that is just circulating the solution though a filter?

yeah the concept is similar. but the practicality is different. You're working with a solution that is highly acidic and corrosive and has copper sulfate which damages even stainless steel. most pumps will dissolve and leave crap into your solution if you use them. The high-quality pumps for corrosive fluids cost hundreds to thousands of dollars.

Most platers doing just plating (no electroforming) get away with just pouring their whole solution through a coffee filter every few days. This does run the problem that the coffee filter itself will breakdown and release contaminants into your bath.

Personally, I adapted a plastic aquarium pump to do my filtering continously.


Keep in mind: the primary source of particulates is the anode itself. As the copper anode dissolves it will drop off flakes of black copper that float around the solution. Therefore most platers place their anodes in a special porous bag that traps the particles but still lets ions flow through. A good bag will greatly reduce filtering issues.

What time frame am I looking at to take a couple pounds of scrap wire and make a couple pound lump? A week? a mouth? Way longer?

depends on what type of bath you're using and what addtives you add. A high quality mix of additives with good bath agitation, continous filtration and precision current control can easily plate a quarter inch of mirror finish copper a week, maybe more (but i've never pushed it).

you could probably make yourself a nice copper plaque in a couple of weeks or so.

Something with no additives, no stirring and no filtering will take a long time. I was able to pull about half-milimeter a week with that setup. Pushing it further with more current only caused massive treeing that gave me a red "rock" that looked nothing like metal.

Sorry to bombard you with questions. I'm just glad to see somone here knows about this!

Remember, safety first, if you have little ones running around or moronic siblings keep this setup out of their reach. You will make a mess of the area you do it in and this unique combination of acids and metal salts will damage things you thought couldn't be damaged (i found that out the hard way).

While i don't normally plug particular companies, here is a company that sells complete plating kits (including those wonderful chemical additives) Plating Kits Electroplating Kits Aluminum Anodizing Kits Powder Coating Systems Metal Polishing And Buffing Supplies - Caswell Inc.

they even include the bucket!


Personally i made all of my own equipment and brewed up my own additives (i'm a chemist) so i never used plating kits and can't really comment on quality. However i've heard nothing but good things from my friends online. Although plating suppliers do tend to overcharge for additives since they are so important and few people understand them. I saw one company charging $100 for enough additives for 500 amp/hours of plating. Personally I can brew the exact same additive for $23 that gives 10 amp/YEARS of plating. So beware of additive price fixing if you decide to use them.


Have fun, and don't sniff the fumes

 

[Andy1845c]

Around these forums you will find designs for constant current power supplies, i suggest you start there.

Personally I built my own switch-mode constant current power supply.

Did you go off a design you found here or somplace online or did you start from scratch?

The link to the plating kit you gave me says 0.07 - 0.2 amps per square inch of part surface area. I would think 5 amps or so would be big enough for me to start off with. Maybe all I would ever need?

Personally, I adapted a plastic aquarium pump to do my filtering continously.

So I take it the acid and copper sulfate don't harm most plastic? Or did you have to search for one that would stand up to it? I see Caswell has a filter kit for 22 dollars. Maybe this would be the easiest route. **broken link removed**

Therefore most platers place their anodes in a special porous bag that traps the particles but still lets ions flow through. A good bag will greatly reduce filtering issues.

I tried looking for these on the Caswell site. Are they refered to as bandages?

Remember, safety first, if you have little ones running around or moronic siblings keep this setup out of their reach. You will make a mess of the area you do it in and this unique combination of acids and metal salts will damage things you thought couldn't be damaged (i found that out the hard way).

Nope no pets or kids around to get into it. Wasn't even planning on doing it at home. I have a small tool repair shop and thought it would make a good spare time project. Does it create clouds of corrosive fumes like muratic acid does though? I don't want to rust everything.

Thanks again for your very informative replys. I don't feel so in the dark now on how this all works.

I think I will try to just start simple with no additives and go from there.
I will work on getting the basic supplys and a power supply and then I am sure I will be back with more questions.

 

[Glyph]

Did you go off a design you found here or somplace online or did you start from scratch?

I started from scratch, but its not as hard as it sounds. Lookup "constant current power supply" on the all-knowing Google and you can find loads of stuff. For your purposes, you can probably get away with simply using a computer PSU and putting some high-wattage resistors to get rid of the excess voltage.

The link to the plating kit you gave me says 0.07 - 0.2 amps per square inch of part surface area. I would think 5 amps or so would be big enough for me to start off with. Maybe all I would ever need?

I have a 200 amp power supply... 99% of the time, its set to 1.4 amps.... 5 amps sounds very reasonable for you. For the longest time i got away with using a 300 ma wall-wort.

So I take it the acid and copper sulfate don't harm most plastic? Or did you have to search for one that would stand up to it? I see Caswell has a filter kit for 22 dollars. Maybe this would be the easiest route. **broken link removed**

acid copper plating baths don't harm most types of water-proof plastic. My plating "tanks" are converted plastic shelves and tupperware containers.


As for the filter, that particular filter is for removing organic contaminants rather than dust particles. Probably wouldn't be good for what you're trying to do.

I tried looking for these on the Caswell site. Are they refered to as bandages?

More properly called "anode bags". Once again, consult the great and powerful Google.

Nope no pets or kids around to get into it. Wasn't even planning on doing it at home. I have a small tool repair shop and thought it would make a good spare time project. Does it create clouds of corrosive fumes like muratic acid does though? I don't want to rust everything.

A perfectly still copper plating tank will not spray anything. If you stir it using air sparging then droplets of the solution will fly out. very vigorous stirring will do that too. and inevitably, when you drop in stuff or pull out dripping stuff, solution will splash out. So Its best just make sure the area is expendable.

If in the future you plane to chrome or nickel plate, or almost any other kind of plating... remember that most plating processes do produce toxic fumes.

Copper though is relatively fume free, just the droplets are the worrisome part.

Still, it never hurts to have good ventilation.

Thanks again for your very informative replys. I don't feel so in the dark now on how this all works.

I think I will try to just start simple with no additives and go from there.
I will work on getting the basic supplys and a power supply and then I am sure I will be back with more questions.

Fun thing to do: spray a non-conductive object (like a leaf or even a dead beetle) with a very thin coating of conductive spray and plate metal onto it. For $0.30 of time effort and chemicals you can make yourself one of those $300 ornaments they sell at gift shops. Just remember its still a dead bug inside and will crush into mush just as easily