Chemistry - Copper layer doesn't stick after Copper electroplating

Solution 1:

Roughen the deposition surface, perhaps by buffing with very coarse sandpaper or an abrasive scrub pad or similar.

If the surface isn't rough enough, the deposited coating has nothing to mechanically "grab onto" and it can be peeled off just as you've observed. With a sufficiently rough surface, the deposition penetrates into the nooks and crannies of the surface texture and adheres very strongly.

Solution 2:

There are a couple factors here:

What you are using for an anode is probably the most important. If you’re not using copper, you’re depleting your copper sulfate electrolyte of copper ions. Use a copper anode and you’ll be continuously replenishing your electrolyte with copper ions.

Concentration of your electrolyte is another factor. If the electrolyte is too weak, you won’t have enough copper ions to continue and you will start electrolyzing water into H+ and and OH-. Since you already have plated out the copper from the copper sulfate, you’re leaving behind the sulfate ions to combine with the OH- ions leaving you with weak sulfuric acid. If it’s too strong when you start, you’ll plate out too much copper too fast (at the beginning) and have poor adherence to your cathode. Alternatively, if your electrolyte doesn’t have enough of a source of sulfate ions, you’ll have too many copper ions which will plate out too quickly and leave you with poor adherence.

Anode to Cathode area ratio is another factor. If the anode is significantly smaller than your cathode, there will be a higher current density at the anode oxidizing faster than the cathode can reduce. This can cause anode polarization due to the uneven oxidation on the surface of the anode. A certain amount of oxidation is necessary for the process, but if it builds up too much, you get too much of your current focused on breaking through the built up oxides it decreases current efficiency and you don’t have as much current for electrodeposition.

If your voltage is too high, you can also start electrolyzing water and if you have hydrogen bubbles being generated at your cathode, the bubbles can prevent a good plate.

If you’re using tap water instead of distilled water for your electrolyte, you can end up with both organic and/or other ions in your electrolyte that can affect the electrochemistry. Some Chloride ions assist in depolarization of the cathode, but too many can cause polarization of the anode.

I actually think one of the most important factors along with your anode material is your cathode material and cleanliness. If your cathode has oils, waxes, soaps or anything else on it, it cam decrease the conductivity of that area, changing your current density and potentially preventing good adherence. If your cathode is made out of a material that is significantly more reactive (iron, zinc, etc) in the reactivity series, you’ll get an immersion “plate” which isn’t actually plating, but cementing copper out of solution which isn’t actually adhering to the surface.

My understanding of is without any formal eduction in chemistry and from my own research and [failed] experiments over the last few months, so please forgive (and correct!) my errors.