Electroplating experiments with an "electrolytic paintbrush"

[Claudio HG]

Hello everybody, not sure this is the right sub-forum for this topic, even though after all an electrolytic paintbrush should be deemed as a tool, right? What's an electrolytic paintbrush? Well, it's a fancy name for a trivial electrode covered with a colth drenched with an electrolyte.
I am sharing my experiments with a simple method for electroplating copper on steel. The video went quite long (>20') but I've tried to explain how the process works and some attempts to improve it, including using lemon juice!
Notice I am not a chemist, so if you spot any mistake please tell me either in the video's comments section or here.
Hope you'll find it interesting. Cheers. Claudio.

[DIYer]

Thanks Claudio HG! We've added your Electrolytic Brush to our Miscellaneous category,
as well as to your builder page: Claudio HG's Homemade Tools. Your receipt:

Electrolytic Brush by Claudio HG

tags: power supply, plating

[nova_robotics]

This is interesting. I have to copper plate some components for an oceanography project I'm working on. Copper is an excellent anti-fouling agent to keep barnacles from clogging up stuff. I started into copper plating, but unfortunately I'm very very lazy. From what I could gather online, you have to nickel plate then copper plate to promote adhesion. I bought a bunch of stuff off of Amazon and that's as far as I got.

[Claudio HG]

Well, that seems the opposite of what I've learnt, whereas copper is used as a base layer upon which nickel can adhere better. But by no means I am an expert in this field, so I could be wrong. By the way, copper plating something that would be put into seawater doesn't sound a good idea to me, as seawater is terribly aggressive and a thin layer of copper wouldn't lasts much. Antifouling agents are based on copper (I) oxide (Cu2O, or cuprous oxide) which is dark red. While copper salts by themselves are relatively toxic for living ornganisms, in seawater copper likely converts into copper chloride oxides rather than cuprous oxides. The former are farily soluble in water while the latter are insuluble. This means the salts are dissolved and corrosion will progress quickly.

[nova_robotics]

You might be right about copper as a base layer. I have absolutely no idea. I'm just repeating what I read online.

Metallic copper can be used as antifouling. Previously old boat hulls would be clad in metallic copper sheets as antifouling, and nets are commonly woven with a metallic copper wire for this purpose. I'm sure cuprous oxide is a lot better than metallic copper, but I don't need the best for this project. I'm coating everything in silicone grease + chilli powder as well.

[Claudio HG]

Metallic copper can be used as antifouling. Previously old boat hulls would be clad in metallic copper sheets as antifouling,

I was aware of that, but the copper cladding in old boats was pretty thick compared to an electroplated layer. That was my point.

I'm coating everything in silicone grease + chilli powder as well.

This is interesting.

[fizzloid]

Many years ago I worked for a company that produced electroplating machines for industry and commercial applications. We would use copper plating as a base coat before plating with other metals, for example Nickel, Chrome or Gold.
We once plated a plaster wall in a clients office with gold; we painted the plaster with a high copper content paint type solution and then plated the solution with a layer of copper followed by Nickel and then 22ct gold.
It came out pretty good, not completely smooth like on metal but really quite shiny and bright.

[Claudio HG]

A plaster wall plated with actual gold? Hhholymoooly was it the office of the "king in the castle"?



Jokes apart, was it cheaper than coating with gold leaf?

[fizzloid]

They already had gold leaf before they contacted my old firm, problem was that it kept flaking off and did not look too good.
The cost was not an issue with that client, but I very much doubt it was cheaper.
The wall was a little over 20 square metres in area. We used custom made 200mm square blocks of glass reinforced carbon covered in a fleece like material with a brass handle, where the anode wire attached, as the 'brushes', and a carbon plate glued to the wall as the cathode connection. The electrolyte fluid carried the plating metal in suspension. The 'brushes' were dipped in trays filled with the electrolyte fluid and then the fluid was applied to the wall. It is a fairly slow process but works well enough. Interestingly, the gold fluid is actually blue before it is used.

[CanBeDone]

If I were to repeat your experiments, first I would replace table salt (=sodium chloride, NaCl) with sodium sulphate (Na₂SO₄), since it electrolyses into oxygen and hydrogen, i.e. it behaves as if it were not present at all, unlike NaCl, which electrolyses into Sodium Hydroxide, Hydrogen and Chlorine gas and consequently changes pH from neutral to strongly alkaline. Since you live in Italy, I've looked up possible suppliers on Amazon.it. (My command of Italian is non-existing, I have to interpret from what I remember of Latin). Solfato di sodio anidro is available from Amazon.it in 500g packs for Euro 12.13. Copper sulphate (solfato di rame) is also available from Amazon.it for 32.75 Euro in 5kg packs. Smaller packs ought to be available from shops supplying swimming pool chemicals, since copper sulphate acts as an effective algicide, substantially lowering the need to add chlorine.
For successful electroplating you need to satisfy two conditions: firstly get enough ions dissolved in your electrolyte so that a decent current can flow. In your experiments, that is the job of adding mainly NaCL. As I wrote above, I would do that by adding Na₂SO₄, since it implies fewer side reactions at the electrodes. The second condition is much harder to satisfy: have enough Cu²⁺ ions in solution so that a sizable portion of your current carries the copper from the anode to the cathode, where it is supposed to be deposited, but not so much that it deposits as loose crystals that do not adhere to your substrate. The fundamentals of how this is to be done are well known. They rely on thermodynamics, i.e. exchanging the concept of concentration for the concept of activity, and in detail look very much like alchemy, not chemistry. You may also want to have a look at the concepts of "Faraday Equation", "redox potential" and "double layer" in Wikipedia, which all shine light on the same issue from rather different viewpoints.
You have taken control of the shape of your deposits by using a brushing action, which is rare, but not new. I first learned about it more than half a century ago, and also learned about its major drawback: you get bored rather soon, think you have done enough, and stop. In reality you have deposited only a very thin layer, which is easily, and quickly, worn off. This layer is also far too porous to stop e.g. rusting.
Have a look at some other approaches to electroplating:
https://www.instructables.com/High-Q...ickel-Plating/
https://www.instructables.com/High-Q...opper-Plating/
How to make copper plating
Galvanization in your garage
Simple nickel plating of steel

Another step I would consider is to replace some of the water with glycol (antifreeze), as this modifies the viscosity of the solution and thus stabilizes the interface electrolyte -> cathode, where the Double Layer resides, since my ultimate goal would be to have a process that I can leave unattended for an hour or even a week.