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The purpose of plastic plating is to coat the surface of the plastic with metal, which not only increases the appearance, but also compensates for the shortcomings of the plastic, gives the nature of the metal, and gives full play to the characteristics of the plastic and the metal. Today, a large number of plastic electroplating products are used in electronics and automobiles , Household goods and other industries.

Process (1) Cleaning: To remove dirt and fingerprints left in the plastic molding process, it can be washed with an alkaline agent and then neutralized with acid dip and washed with water.

(2) Solvent treatment: Wetting the plastic surface so as to interact with the conditioner in the next step. (3) Conditioning: Roughening the plastic surface into interlocking cavities to make the coating tightly adhered is not easy to peel, also known as chemical roughening.

(4) Sensitization (sensitization): The reducing agent is adsorbed on the surface, commonly used (stannous chloride) or other tin compounds, that is, the adsorption of sn^++ ions on the plastic surface has a reducing surface.

(5) Nucleation: The catalytic substance such as gold is adsorbed on the sensitized (reducing) surface, and nodules are noduled into a catalytic metal seed by reduction, which can then be used for electroplating metal. The reaction is as follows: sn+ + pd+ = sn4+ + pdsn+ +2ag+ = sn4+ +2ag

The formulation consists of a solvent treatment solution: including washing: washing with no dilute acid or neutral washing and 1 to 2% interface activator. Mix and immerse at 40 to 65°C for 1 to 2 minutes.

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

Conditioning (conditioning): chemical roughening, 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℃ for 10～20 minutes

Sensitizing: stannous chloride sncl2 20～40 g/l hydrochloric acid hcl 10～20 cc/l

Tuberculosis (nucleation) or activation (activation) Example 1 palladium chloride pdcl2 0.1～0.3g/l hydrochloric acid hcl 3～5 cc/l Example 2 silver nitrate agno3 0.5～5 g/l appropriate amount of ammonia Example 3 gold chloride aucl3 0.5～ 1 g/l hydrochloric acid hcl 1～4 cc/l

Influencing factors

There are many types of plastic, but not all plastics can be electroplated. Some plastics and metal layers have very poor binding strength and have no practical value; some plastics and metal coatings have certain physical properties such as expansion coefficients that are too different, making it difficult to guarantee their performance in high temperature environments. At present, the most used for electroplating is ABS, followed by PP. In addition, PSF, PC, PTFE, etc. also have successful plating methods, but it is more difficult.

Plastic parts modeling

On the premise of not affecting the appearance and use, the plastic parts should be designed to meet the following requirements as much as possible.

(1) The metallic luster will make the original shrinkage more obvious, so avoid the uneven wall thickness of the product to avoid shrinkage, and the wall thickness should be moderate to prevent the wall from being too thin (less than 1.5 mm), otherwise It will cause poor rigidity, easy to deform during electroplating, poor adhesion of the coating, and also easy to deform during use, causing the coating to fall off.

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

(3) The sharp edge becomes thicker in the electroplating process. The sharp edges in the electroplating can cause tip discharge, causing the corner plating to bulge. Therefore, fillet transition should be used as much as possible, with a radius of at least 0.3 mm. Flat-shaped plastic parts are difficult to electroplate. The central part of the plating is thinner. The thicker the coating is, the more uneven the coating is. The plane shape should be changed to a slightly rounded surface or made of orange peel. . The greater the surface area of the plating, the greater the difference in gloss between the center and the edge. A slight parabolic surface can improve the uniformity of the gloss of the plating surface.

(4) Minimize the number of grooves and protrusions on the plastic parts. Because in the electroplating, the deep concave part is easy to expose, and the protruding part is easy to scorch. The depth of the groove should not exceed 1/3 of the groove width, and the bottom should be rounded. When there is a grille, the hole width should be equal to the beam width and less than 1/2 of the thickness.

(5) The plated parts should be designed with sufficient mounting positions, and the contact surface with the hangers should be 2 to 3 times larger than the metal parts.

(6) The design of the plastic parts should make the parts easily demolded when sinking, otherwise the surface of the plated parts may be scratched or sprained during forced demoulding, or the internal stress of the plastic parts may be affected to affect the bonding force of the plating layer.

(7) When knurling is required, the knurling direction should be consistent with the demolding direction and linear. The distance between the knurling stripes and the stripes should be as large as possible.

(8) Try not to use metal inserts for plastic parts, otherwise the inserts will be easily corroded during pre-plating treatment.

(9) The surface of plastic parts should be guaranteed to have a certain surface roughness.

Compared with metal parts, plastic electroplating products can not only achieve a good metal texture, but also reduce the weight of the product. While effectively improving the appearance and decoration of plastic, it also improves its electrical, thermal and corrosion resistance. The performance improves its surface mechanical strength. However, the selection of plastic materials for electroplating should comprehensively consider factors such as material processing performance, mechanical performance, material cost, electroplating cost, difficulty of electroplating, and dimensional accuracy. Because of its structural advantages, ABS plastics not only have excellent comprehensive performance, are easy to process and form, and the material surface is easily eroded to obtain a higher plating adhesion, so it is currently widely used in electroplating.

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