Electroplating requires a lowvoltage and high current power supply to the electroplating tank and an electrolytic device composed of electroplating solution, parts to be plated (cathode) and anode. The composition of electroplating solution varies with the coating, but all of them contain the main salt which provides metal ions, and the complexing agent which can complexing the metal ions in the main salt to form complex. It is used as buffer, anode activator and special additives (such as brightener, grain refiner, leveling agent, wetting agent, stress relief agent and mist suppressor) to stabilize the pH value of solution. The electroplating process is a process in which the metal ions in the plating solution are reduced to metal atoms through electrode reaction under the action of external electric field, and the metal is deposited on the cathode. Therefore, this is a metal electrodeposition process including liquid mass transfer, electrochemical reaction and crystallization.
. The electroplating solution consists of an aqueous solution containing plating metal compounds, conductive salts, buffers, pH regulators and additives. After being electrified, the metal ions in the plating solution move to the cathode to form the coating under the action of potential difference. The anode metal forms metal ions into the plating solution to maintain the concentration of the metal ions to be coated. In some cases, such as chrome plating, it is an insoluble anode made of lead and lead antimony alloy, which only plays the role of transferring electrons and conducting current. The concentration of chromium ion in the electrolyte should be maintained by adding chromium compound to the bath regularly. During electroplating, the quality of anode material, composition of electroplating solution, temperature, current density, power on time, stirring strength, precipitated impurities, power waveform, etc. will affect the quality of the coating, which needs to be timely controlled.
Firstly, the electroplating solution has six elements: main salt, additional salt, complexing agent, buffer, anode activator and additive.
Electroplating principle includes four aspects: electroplating solution, electroplating reaction, electrode and reaction principle, and electrodeposition process of metal.
Electrochemical reaction in electroplating reaction: the following figure is the schematic diagram of the electroplating device. The plated parts are cathodes, which are connected with the negative pole of the DC power supply. The metal anode is connected with the positive pole of the DC power supply. Both the anode and the negative are immersed in the plating solution. When a certain potential is applied between the anode and the cathode, the reaction takes place at the cathode as follows: the metal ion Mn + diffused from the inside of the plating solution to the interface between the electrode and the plating solution obtains n electrons from the cathode and reduces to metal M. On the other hand, the opposite reaction occurs at the anode, that is, the dissolution of metal M occurs at the anode interface, releasing n electrons to form metal ion Mn +.