Preparation before electroplating of stainless steel plate

Preparation before electroplating of stainless steel plate Stainless steel plate is easily passivated in air to form a dense passivation film, which has good corrosion resistance. With the development of various industries, the application of stainless steel has expanded rapidly, resulting in an increasing demand for functional electroplating on stainless steel. The difficulty of stainless steel electroplating is concentrated on the bottom electroplating of stainless steel. If the bottom electroplating of stainless steel is solved, the conventional electroplating method can be used to realize multi-layer electroplating. The difficulty of bottom plating lies in the pretreatment of stainless steel. Improper pretreatment will often result in delamination, peeling, and peeling of the coating. Process flow The process flow is: organic solvent immersion degreasing→water washing→chemical degreasing→water washing→pickling→water washing→activation and pre-plating→pre-nickel plating→water washing→copper plating→water washing→nickel plating, silver plating and other electroplating→water washing →Drying→Packing. The difficulty in the pretreatment of stainless steel electroplating lies in how to destroy the passivation layer on the stainless steel surface and the activation of the stainless steel substrate. It is preliminarily determined that chemical treatment will be used to completely destroy the passivation layer on the surface of stainless steel. Then in the pre-plating solution, the surface of the metal substrate is further activated without electricity, and a layer of metal nickel is quickly plated by electrodeposition before the new passivation layer is formed, so as to realize the bottom plating of stainless steel. The main process of pretreatment shows that some stainless steel parts can not be degreasing by electrochemical degreasing method. Because some stainless steel parts become black and black after electrochemical degreasing, the surface cannot be brightened even with pickling. In order not to destroy the bright state of the stainless steel surface, first use industrial gasoline to scrub the oil on the surface, and then use industrial detergent to heat it to 50-70 ℃ for degreasing. Chemical degreasing uses chemical degreasing to remove oil stains on the surface of parts again. The technical specifications for degreasing are: NaOH60～80g/L, Na2CO320～40g/L, Na3PO450～70g/L, Na2SiO310～15g/L, 50～70℃, 3～5min. When removing oil, be sure to control the temperature and time of the bath liquid. If the degreasing time is too short, the oil stain on the stainless steel surface cannot be completely removed; if the degreasing time is too long, the surface of the stainless steel will be rough, which will affect the roughness of the surface. Pickling Pickling is an essential process in the pretreatment process of stainless steel electroplating. Because pickling can not only remove the rust on the surface of the stainless steel, but also destroy the oxide film on the surface, so that the substrate of the surface layer is exposed, and the bonding force of the pre-plating layer can be greatly increased. The technical specification of pickling is: 30% HCl200～300g/L, 15～25℃, 2～5min. The purpose of activation is to remove the oxide film on the surface of the stainless steel, activate the surface, and ensure that the coating has sufficient adhesion to the stainless steel substrate. The activation process includes impregnation activation and cathodic activation. After experiments, we immersed and activated stainless steel to quickly remove the oxide film on the surface, and then carried out electrochemical pre-plating treatment to quickly generate a layer of coating, which greatly improved the adhesion between the coating and the stainless steel. The technical specification of chemical activation is: 30% HCl200～300g/L, 15～25℃, 2～5min.

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