Galvanized square pipe processing is to deposit a metal or alloy layer on the surface of the product through the electrolysis process of metal ions to change the physical and chemical properties of the product surface, and ultimately make the galvanized sheet wearable, decorative and impact-resistant. In addition, it can be coated according to the special requirements of specific products. Certain coatings, such as photoelectric and electromagnetic coatings, can fully expand the application field of galvanized rectangular tubes.
The production specifications of galvanized rectangular tube are: square tube: 20 x 20 x 1.3-500 x 500 x 16 mm; rectangular tube: 20 x 30 x 1.3-400 x 600 x 16 mm.
The galvanized rectangular tube processing and electroplating process mainly includes pretreatment, electroplating and post-treatment. The quality of the coating depends on the electroplating process of the material, and the electroplating process is affected by many factors. Six factors are summarized as follows:
Zinc content: The higher the zinc purity of zinc block is, the narrower the brightness range is, the thicker the coating can be obtained and the lower the iron content in the coating will be. When the zinc block is too low in purity, the brightness range will be wider, and it will take longer to reach the required zinc layer thickness, which will lead to higher iron content in the zinc plating layer. .
2. Sodium hydroxide: Sodium hydroxide has dual effects on the reaction. When the content of sodium hydroxide is too high, burning phenomenon is easy to occur during high temperature operation. When the content of sodium hydroxide is too low, the dispersibility of solution is poor, which will reduce the quality of zinc layer.
3. Iron content: When the iron content is too high, the iron content in the coating will correspondingly be more, which will lead to the inadequate brightness of passive film; and the low iron content will lead to the low iron content in the galvanized coating, which will reduce the corrosion resistance of automobile panels, and will lead to olive color on the surface of automobile panels.
4. Brightener: The brightener used now is composed of ZF-100A and ZF-100B. The former concentration is too high to enhance the brittleness of the coating, while too low to cause the coating in the low current zone to be sparse, resulting in non-uniform passivation.
5. Temperature: High temperature in the process of electroplating will lead to the decrease of Solution Dispersion ability, the increase of iron content in the coating, and the non-uniform passivation; and when the reaction temperature is too low, the high current density zone will easily burn, the brittleness of the coating is greater and the deposition rate is slower.
6. Cathode moving speed: In the process of electroplating, the cathode must be kept in a moving state. If the moving speed is too fast, the coating in the high current density area will be rough; and if the moving speed is too slow, airflow may occur, resulting in the uneven coating of materials.
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