Plastic plating-basic plating process
Huizhou City Boluo Tenglong Technology Co., Ltd. wholeheartedly serves you! Mainly engaged in plastic water electroplating processing, accompanying plastic injection molding processing, mold processing and so on!
1. Basic procedures
(Polishing → polishing)→ hanging → degreasing and degreasing → water washing →(electrolytic polishing or chemical polishing)→ acid washing activation →(pre-plating)→ electroplating → water washing →(post-treatment)→ water washing → drying → hanging → inspection packaging
2. The role of each process
1. Pre-treatment: All processes before plating are called pretreatment. The purpose is to trim the surface of the workpiece and remove grease, rust scales, oxide films, etc. on the surface of the workpiece to provide the required plating surface for subsequent plating deposition. Pretreatment mainly affects the appearance and adhesion. According to statistics, 60% of defective plating products are caused by poor pretreatment, so pretreatment plays a very important role in the electroplating process. In countries with developed electroplating technology, great importance is attached to pretreatment processes, which account for half or more of the entire electroplating process, so that coatings with good surface conditions can be obtained and defective rates can be greatly reduced.
Sand blasting: Remove rust, welding slag, carbon deposits, old paint layers, and other dry oil stains on the surface of parts; Remove sand and oxide scales on the surface of castings, forgings or heat treated parts; Remove burrs and directional wear marks on the surface of parts; Reduce the roughness indicated by parts to improve the adhesion of paints and other coatings; Make parts appear in a diffuse reflective extinction state
Polishing: Remove various macro defects such as burrs, rust, scratches, welds, weld bumps, sand holes, and oxide scales to improve the flatness and plating quality of the parts.
Polishing: The purpose of polishing is to further reduce the roughness of the part surface and obtain a bright appearance. There are mechanical polishing, chemical polishing, electrochemical polishing and other methods.
Degreasing and degreasing: Remove grease from the workpiece surface. There are organic solvent degreasing, chemical degreasing, electrochemical degreasing, wiping degreasing, roller degreasing and other methods.
Pickling: Remove rust and oxide film on the surface of the workpiece. There are chemical acid cleaning and electrochemical acid cleaning.
2. Electroplating
Obtaining the required coating on the surface of the workpiece is the core process of electroplating processing. The quality of this process directly affects the various properties of the coating. The factors that have an important impact on the coating in this process mainly include the following aspects:
① Main salt system
Each plating type will develop a variety of main salt systems and supporting additive systems. For example, zinc plating includes cyanide zinc plating, zincate zinc plating, chloride zinc plating (or called potassium salt zinc plating), ammonia zinc plating, sulfate zinc plating and other systems.
Each system has its own advantages and disadvantages, such as good dispersion and depth of the cyanide zinc plating solution, fine crystallization of the coating, good adhesion to the substrate, good corrosion resistance, wide process range, stable and easy operation of the plating solution and less sensitive to impurities. However, it is highly toxic and seriously pollutes the environment. Chloride zinc plating bath is a single salt plating bath without complexing agents, and wastewater is easy to treat; the brightness and leveling of the coating are better than other systems; the current efficiency is high and the deposition speed is fast; steel with low hydrogen overpotential such as high-carbon steel, castings, forgings, etc. are easy to coat. However, due to the weak acidity of chloride ions, it has certain corrosiveness to the equipment. On the one hand, it will cause certain corrosion to the equipment. On the other hand, this kind of plating solution is not suitable for deep holes or tubular parts that require auxiliary anodes.
② Additives
Additives include glossing agents, stabilizers, softeners, wetting agents, low-area positioning agents, etc. Gloss agents are divided into main gloss agents, carrier brighteners and auxiliary gloss agents. For the same main salt system, additives made by different manufacturers are used, and the quality of the coatings obtained will vary greatly. Overall, developed countries such as Europe, America and Japan have the best additives, followed by Taiwan, and those produced in mainland China are relatively inferior to the first two categories.
The combination of the main salt and a specific manufacturer's additive determines the overall performance of the plating solution used. Excellent additives can make up for the shortcomings of some properties of the main salt. For example, the deep plating ability of the plating solution obtained by combining excellent chloride zinc plating additives with chloride main salts is better than the depth ability of many cyanide zinc plating baths.
③ Electroplating equipment
(1) Hanging tool: Square hanging tool is used in conjunction with square plating bath, and circular hanging tool is used in conjunction with circular plating bath.
(2) Circular plating tanks and hangers are more conducive to ensuring uniform current distribution. For square hangers, current dispersion devices such as barbed wire mesh need to be added around the hangers or the length of anode plates on both sides should be shortened, and the oval anode as shown in the figure should be used. layout.
(2)Stirring device: Promote solution flow, distribute solution state evenly, and eliminate bubble retention on the surface of the workpiece.
(3)Power supply: DC, good stability, small ripple coefficient.
3. Post-processing
After electroplating, various treatments are carried out to enhance various properties of the coating, such as corrosion resistance, anti-discoloration ability, solderability, etc.
Dehydration treatment: Add dehydrating agent to the water, such as post-treatment after bright nickel plating
Passivation treatment: improves corrosion resistance of coating, such as zinc plating
Anti-discoloration treatment: Add anti-discoloration agents to water, such as silver plating, tin plating, imitation gold plating, etc. to improve solderability treatment: such as tin plating
Therefore, the quality of the post-treatment process directly affects the quality of these functions of the coating.
