My first attempt to copper electroplate 3D print
So I want to experiment with copper electroplating 3D prints (later: nickel).
This is the first experiment, so a long shot of being usable, but it gave some learnings.
I started with making the printed object conductive (I used some leftover older print in my scrap box).
To get a conductive surface I used carbon paint (MG Chemicals 838 - the first thing I could find that roughly met my idea). After three coats and drying, I got a surface resistance of about 1kΩ across the part. Not great, but should be enough.
As bath, I used a simple CuSO₄ solution; I used about 0.4 mol per liter (dissolved in distilled water). I didn’t have any sulfuric acid at home, which would be another recommended ingredient - mostly to dilute the copper concentration I presume. So anyway, I went with the straight copper sulfate solution. Plus a little drop of dish-washing detergent to reduce surface tension.
I started with about 80mA current, but due to the fact that the part is hardly conductive, most copper went straight to the connecting wire. So then I only half-immersed it, that the wire was not directly touching the electrolyte, later turned it around. I got some burn-marks when I attempted to crank up the current (high contact resistence = heat :)). These are the ‘holes’ in the result.
I didn’t get much coverage in the ‘inner’ parts - I presume mostly because the current density was not high there in the first place, and once the highly conductive copper was covering the other parts, these were essentially left alone.
I used a piece of a copper pipe and some copper scrubbers as anode.
After the piece was mostly covered with a thin layer of copper (80mA over night), I cranked it up, fully immersed, to 400mA (voltage was around 1.2V, so pretty low resistance electrolyte). For about 4h.
After taking out the part, it was a bit dull, so I scrubbed it with bathroom scrub detergent, which brought a bit of shine to it (I didn’t go fully to town on this, but looks like it can be made shiny).
First important learning is, that I need to accommodate the initial high resistance of the part, so that all areas of it get an equal chance to get covered. I presume I should start with a highly diluted electrolyte with a high inner resistance to impedance match the part - then the relative resistance of the connecting wire vs. the part vs. deep pockets in the part is not too high. Once a thin layer of copper is on there, put it in the more concentrated electrolyte.
Second learning: 400mA seemed to be too much, looks like little clumps of copper collected in some spots. Maybe this will be better if I have the full solution with sulfuric acid. Need to normalize per surface area.
Third learning: the anode gets messy and little parts drop down; probably I should contain that in e.g. nylon stocking (also less likely to accidentally short when moving the part).
ToDo: Get battery acid (sulfuric acid) and metal polishing stuff. And probably implement a function in OpenSCAD that returns the surface area of a module, so that I don’t have to calculate that part by myself.
Most important learning: looks promising. In particular, the adhesion seems to be pretty good.
