Electroplating is an electrochemical process as well as a redox process The basic process of electroplating is to immerse the parts in the solution of metal salt as the cathode and the metal plate as the anode. After being connected to the DC power supply, the required coating is deposited on the parts. For example, in nickel plating, the cathode is the part to be plated, and the anode is pure nickel plate. The following reactions occur at the anode and cathode respectively:
Cathode (plated part):ni2++2e → Ni (main reaction)
2h++2e → H2 ↑ (side reaction)
Anode (nickel plate):ni-2e → ni2+ (main reaction)
4OH- － 4E → 2h2o+o2 (side reaction)
Not all metal ions can be deposited from aqueous solution. If the side reaction of hydrogen ion reduction to hydrogen on the cathode is dominant, it is difficult for metal ions to precipitate on the cathode According to experiments, the possibility of electrodeposition of metal ions from aqueous solution can be obtained from the periodic table of elements.
Anodes are divided into soluble anodes and insoluble anodes. Most anodes are soluble anodes corresponding to the coating, such as zinc anodes for zinc plating, silver anodes for silver plating, and tin lead alloy anodes for tin lead alloy. However, a few electroplating uses insoluble anodes due to difficulties in anode dissolution. For example, platinum or titanium anodes are mostly used for acid gold plating, and the main salt ions of the plating solution are supplemented by adding the prepared standard gold containing solution, Chromium plated anodes use pure lead, lead tin alloy, lead antimony alloy and other insoluble anodes.
