The purpose of plastic electroplating is to coat the plastic surface with metal, which not only increases the beauty, but also compensates for the shortcomings of plastic, endows the properties of metal, and gives full play to the characteristics of plastic and metal. Today, a large number of plastic electroplating products are used in electronics, automobile, household products and other industries.

Process (1) cleaning: remove the dirt and fingerprints left in the plastic forming process, wash with alkali, then neutralize with acid immersion and wash with water.

(2) Solvent treatment: the plastic surface can be wetted to act with the conditioner in the next step（ 3) Conditioning: coarsening the plastic surface into an internally locked concave hole to make the coating close and not easy to peel off, also known as chemical coarsening.

(4) Sensitization: adsorb the reducing agent on the surface, commonly used (stannous chloride) or other tin compounds, that is, Sn ^ + + ions are adsorbed on the plastic surface with reducing surface.

(5) Nucleation: the catalytic substances such as gold are adsorbed on the sensitive (Reductive) surface, and then reduced into catalytic metal seeds, which can then be used for metal electroplating. The reaction is as follows: Sn + + PD + = Sn4 + + PDSN + + 2ag + = Sn4 + + 2ag

Formula composition: solvent treatment solution: including cleaning: cleaning without dilute acid or neutral cleaning and 1 ~ 2% interface activator. Mix and soak at 40-65 ℃ for 1 ~ 2 minutes.

Solvent treatment: acetone, diacetate, methane and other active agents.

Conditioning: chemical coarsening and chemical etching. Example 1 anhydrous chromic acid CrO3 20 g / L sulfuric acid H2SO4 specific gravity 1.84 600cc / L liquid temperature 60 ℃ time 15 ~ 30 minutes example 2 anhydrous chromic acid CrO3 20 g / L phosphoric acid h3po3 100 cc / L sulfuric acid H2SO4 500 cc / L liquid temperature 69 ℃ time 10 ~ 20 minutes

Sensitizing: stannous chloride SnCl 2 20 ~ 40 g / L HCl 10 ~ 20 cc / L

Tuberculosis or activation case 1 palladium chloride PdCl 2 0.1 ~ 0.3g/l HCl 3 ~ 5 cc / l case 2 silver nitrate AgNO 3 0.5 ~ 5 g / L ammonia appropriate case 3 gold chloride AuCl 3 0.5 ~ 1 g / L HCl 1 ~ 4 cc / L

Influencing factors material selection of plastic parts

There are many kinds of plastics, but not all plastics can be electroplated. Some plastic and metal layers have poor adhesion and have no practical value; Some physical properties such as expansion coefficient of some plastics and metal coatings are too different, so it is difficult to ensure their performance in high temperature difference environment. At present, ABS is the most used for electroplating, followed by PP. In addition, PSF, PC and PTFE also have successful electroplating methods, but it is difficult.

Plastic part modeling

On the premise of not affecting the appearance and use, the plastic part modeling design shall meet the following requirements as far as possible.

(1) The metal luster will make the original shrinkage more obvious. Therefore, the uneven wall thickness of the product should be avoided to avoid shrinkage, and the wall thickness should be moderate to avoid the wall being too thin (less than 1.5 mm), otherwise it will cause poor rigidity, easy deformation during electroplating, poor adhesion of the coating, and easy deformation and falling off of the coating during use.

(2) Avoid blind holes, otherwise the treatment solution remaining in the blind holes is not easy to clean, which will cause pollution in the next process and affect the electroplating quality.

(3) The phenomenon of sharp edge thickening occurs in electroplating process. Sharp edges in electroplating will cause tip discharge and cause bulge of corner coating. Therefore, fillet transition shall be adopted as far as possible, and the fillet radius shall be at least 0.3 mm. Plate shaped plastic parts are difficult to electroplate. The central part of the plated parts has a thin coating, and the coating closer to the edge is thicker. The whole coating is uneven. The plane shape should be changed to a slightly circular arc surface or made into a matte surface with orange peel pattern. The larger the surface area of electroplating, the greater the difference between the gloss of the center and the edge. A slight paraboloid can improve the uniformity of the gloss of the plated surface.

(4) Reduce grooves and protrusions on plastic parts as much as possible. Because when electroplating, the deep concave part is easy to expose plastic, and the protruding part is easy to be burnt. The groove depth shall not exceed 1 / 3 of the groove width, and the bottom shall be circular arc. When there is grating, the hole width shall be equal to the beam width and less than 1 / 2 of the thickness.

(5) Sufficient mounting positions shall be designed on the plated parts, and the contact surface with the hanger shall be 2 ~ 3 times larger than the metal parts.

(6) The design of plastic parts shall make it easy to demould when the parts are sinking, otherwise the surface of plated parts will be strained or twisted during forced demoulding, or the internal stress of plastic parts will be caused and the adhesion of plating will be affected.

(7) When knurling is required, the knurling direction shall be consistent with the demoulding direction and in a straight line. The distance between knurling stripes and stripes shall be as large as possible.

(8) Plastic parts shall not use metal inserts as far as possible, otherwise the inserts are easy to be corroded during pre plating treatment.

(9) The surface of plastic parts shall have a certain surface roughness.

Advantages compared with metal parts, plastic electroplated products can not only achieve good metal texture, but also reduce the weight of products. While effectively improving the appearance and decoration of plastics, they also improve their electrical, thermal and corrosion resistance properties, and improve their surface mechanical strength. However, the selection of plastic materials for electroplating should comprehensively consider the processing performance, mechanical properties, material cost, electroplating cost, electroplating difficulty and dimensional accuracy of materials. Because of its structural advantages, ABS plastic not only has excellent comprehensive properties and is easy to process and shape, but also the material surface is easy to erode and obtain high coating adhesion, so it is widely used in electroplating at present.

With the rapid development of industry and the increasingly wide application of plastic electroplating, it has become one of the important means of surface decoration in plastic products. At present, electroplating has been widely carried out on ABS, polypropylene, polysulfone, polycarbonate, nylon, phenolic glass fiber reinforced plastics, polystyrene and other plastic surfaces at home and abroad, especially ABS plastic electroplating is the most widely used and the electroplating effect is the best