What is the principle of electrochemical cleaning of PVD vacuum instruments?
The electrochemical cleaning of PVD vacuum coating equipment refers to putting the metal parts to be cleaned in the solution, and connecting the parts to the positive or negative electrode of the power supply, and connecting the other electrode of the power supply to the electrode plate made of a certain material. The power supply voltage is adjusted appropriately in order to obtain a certain current density, and finally obtain the effect of degreasing and removing the oxide layer on the metal surface. The efficiency of electrolytic degreasing is much higher than that of chemical degreasing.
The distance between electrodes for electrolytic degreasing is usually 5cm~15cm, equipped with a power supply voltage of 2V~12V. The principle of electrolytic degreasing: During electrolysis, bubbles will be generated on the electrode (the bubbles generated on the anode are O₂, and the bubbles generated on the cathode are H₂). Due to the impact of mechanical force, a thin layer of grease adheres to the part. At the same time, the oil and lye have the functions of saponification and emulsification respectively, which accelerates the speed of oil removal.
In the case of deep pits on the vacuum coating equipment parts, electrochemical cleaning should be used in conjunction with lye degreasing. In addition, when the parts are connected to the cathode (the cathode is de-oiled), the H₂ generated by the cathode can penetrate into the interior of some metal materials, causing the metal to become brittle. For this type of metal material, we generally can only use The way of anode degreasing.
Electrolytic degreasing formula and electrolytic specifications:
1. Caustic soda (NaOH): 60g/L;
2. Soda ash (Na₂CO₃): 20g/L;
3. Sodium oxide (NaCN): 20g/L;
4. Water glass (Na₂SiO₃): 8g/L;
5. Voltage (the parts are connected to the cathode, and stainless steel is used as the anode): 6V~10V;
6. Current density: 40mA/cm²~80mA/cm²;
7. Temperature: 25°C;
8. Time: 1min~2min.
Electrolytic etching is also divided into two types: anode etching and cathodic etching. The use of anode etching can easily make parts etched unevenly, while cathodic etching is prone to hydrogen seepage and brittleness. The process of electrolytic etching of pvd vacuum coating equipment is the same as that of electrolytic degreasing. Compared with conventional etching methods, electrolytic etching is more effective for the etching effect of certain metals, which can shorten the etching time, reduce the consumption of the solution, and obtain a better cleaning effect than chemical etching.
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