Electroplating Process Principle

- Jan 11, 2018 -

Electroplating Process Principle

Process principle

Plating requires a low-voltage, high-current power supply to the bath and an electrolyzer consisting of the bath, the part to be plated (cathode) and the anode. The composition of the plating solution varies depending on the coating, but each contains a main salt that provides a metal ion, a complexing agent that can complex the metal ion in the main salt to form a complex, a buffer for stabilizing the pH of the solution, an anode activator and Special additives (such as brighteners, grain refiners, levelers, wetting agents, stress relievers and fog suppressants, etc.). Electroplating process is the metal ions in the bath under the action of an external electric field, the electrode reaction is reduced to metal atoms, and the metal deposition process on the cathode. Therefore, this is a metal electrodeposition process including liquid phase mass transfer, electrochemical reaction and electrocrystallization.

In the plating bath containing plating solution, after cleaning and special pretreatment to be plated as a cathode, the anode is made of plated metal, the two poles are respectively connected with the positive and negative poles of the direct current power supply. The plating solution is composed of an aqueous solution containing a metal-plating compound, a conductive salt, a buffer, a pH adjuster, an additive and the like. After electrifying, the metal ions in the plating solution move to the cathode to form a plating layer under the effect of the potential difference. The anode metal forms metal ions into the plating bath to maintain the concentration of the metal ions to be plated. In some cases, such as chrome plating, an insoluble anode made of lead and lead-antimony alloy is used only to transmit electrons and conduct current. The concentration of chromium ions in the electrolyte needs to be maintained by periodically adding a chromium compound to the bath. Electroplating, the quality of the anode material, the composition of the bath, temperature, current density, power time, stirring intensity, precipitated impurities, power waveform will affect the quality of the coating, the need for timely control.

First of all there are six plating elements: main salt, additional salt, complexing agent, buffer, anode activator and additive.

Plating principle contains four aspects: plating solution, electroplating reaction, the electrode and the reaction principle, the metal electrodeposition process.

Electrochemical reaction in electroplating reaction: The following diagram shows the schematic diagram of the electroplating apparatus. The plated part is the cathode, connected to the negative electrode of the DC power supply, the positive electrode of the metal anode is connected with the positive electrode of the DC power supply, and the anode and the cathode are immersed in the plating solution. When a certain potential is applied between the yin and yang, the following reaction occurs at the cathode: Metal ions Mn + diffused from the inside of the plating solution to the interface between the electrode and the plating solution obtain n electrons from the cathode and are reduced to the metal M. On the other hand, at the anode, the reaction completely opposite to the cathode occurs, that is, the dissolution of the metal M occurs at the anode interface, and n electrons are generated to generate the metal ions Mn +.

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