Copper can be coated with Nickel using electrolysis(electro plating) or by an electroless process(autocatalytic phosphorus nickel), while the electroless process seems to be quite simple and inexpensive, the fact is that there are many metals like copper that are not catalytic to the process and can not be coated without using an expensive palladium chloride activator solution(palladium is quite expensive).
Enter Contact Plating discovered by Henry Bessemer in 1831 (Graham's Electroplating Engineering Handbook) it fell into obscurity shortly after electroplating became practical, but I still believe the process has merits especially for small/medium copper pieces like jewelr.
What is contact plating?
In Contact Plating we place a noble metal(Copper with a positive standard reduction potential) in contact with a more reactive metal like Aluminum(negative standard reduction potential), in an electrolyte solution of the metal we want to deposit, in this case Nickel Chloride, Nickel Chloride reacts with aluminum creating aluminum chloride and nickel metal(2 Al(s) + 3 NiCl2(aq) = 2 AlCl3(aq) + 3 Ni ) and while Copper is kept in contact with aluminum it's temporarily charged with Aluminums negative reduction potential charge and is electrically coated with Nickel.
Standard Reduction Potentials in Aqueous Solution.
Step 1: Equipment and Chemicals Need It
1. Heat source to keep electrolytic solution at 80/90 celsius(I used an electric hot plate).
2. Source of Aluminum container(I used a cast aluminum skillet).
3. Nickel Chloride(Saturated solution, one litter).
4. Safety Gear.
5. Pieces to be coated with Nickel(I cut some Copper piping to simulate Copper articles/Jewelry).
Step 2: Nickel Coating
Just heat the skillet and the Nickel Solution and placed the Copper articles(previously polished and properly cleaned and degreased), move/turn the pieces from time to time so they get coated evenly, about 5 minutes for a thin coat, you can leave it longer for a thicker coat of Nickel.