n simple terms, electroplating refers to the use of external direct current to perform an electrolytic reaction in a solution to deposit a metal or alloy layer on the surface of a conductor such as a metal. We use copper sulfate plating bath as an example: Copper sulfate plating bath mainly contains copper sulfate, sulfuric acid and water, and even other additives.

           Copper sulfate is the source of copper ions (Cu2 +). When dissolved in water, copper ions are dissociated, and copper ions are reduced (get electrons) at the cathode (workpiece) to deposit metal copper. This deposition process will be affected by the conditions of the plating bath such as copper ion concentration, pH (pH), temperature, agitation, current, additives, etc. The main reaction of the cathode: Cu2 + (aq) + 2e- → Cu (s) The concentration of copper ions in the bath decreases due to consumption and affects the deposition process.

Faced with this problem, there are two ways to solve it:

1. Add copper sulfate in the bath;

2. Use copper as the anode. The method of adding copper sulfate is troublesome, and analysis and calculation are needed. It is relatively simple to use copper as the anode. The role of the anode is mainly a conductor, which connects the circuit loop. However, copper has another function as an anode, which is to oxidize (lost electrons) and dissolve into copper ions to supplement the consumption of copper ions.

        Anode reaction: Cu (s) → Cu2 + (aq) + 2e- Since the whole plating solution mainly contains water, the side reactions of water electrolysis to generate hydrogen (on the cathode) and oxygen (on the anode) also occur. Cathode side reaction: 2H3O + (aq) + 2e- → H2 (g) + 2H2O (l) Anode side reactions: 6H2O (l) → O2 (g) + 4H3O + (aq) + 4e- As a result, the surface of the workpiece was covered with a layer of metallic copper. This is a typical plating bath mechanism, but the actual situation is very complicated. Self-catalytic plating and dip plating.