Abstract: Pearl nickel has an elegant appearance, soft color and a satin-like surface. It is gradually replacing the decorative coating with dazzling luster for parts and decorative parts of automobiles, motorcycles and household appliances. Three preparation methods of pearl nickel were introduced, including mechanical method, composite plating method, emulsifier method, and electroplating process of the latter two methods. The mechanism of action of additives in the process of forming satin coating was discussed. The development status of pearl nickel at home and abroad is reviewed, and the research direction of domestic pearl nickel is proposed.
Key words: pearl nickel; electroplating; additive; emulsifier; satin coating
1 Introduction In recent years, with the rapid development of the electroplating industry and the gradual transformation of people's aesthetic views, in addition to the functional coatings of special needs, more and more decorative electroplating has been widely welcomed by the society [1]. The pearl nickel plating has a satin-like luster, giving a soft and comfortable feeling. It feels smooth, elegant and feminine, like a pearl surface, and is very popular among people [2]. The pearlescent nickel plating has a slightly lustrous color and a soft color to avoid eye fatigue. Therefore, it is widely used, such as mobile phone casings, camera casings, handicrafts, interior decoration parts, household appliances, decorative parts, auto parts, and clock accessories. Kitchen utensils and eye frames. Electroplating decorative chrome, bright silver or bright gold on pearl nickel plating to form sand chrome, sand gold or sand silver can meet different hobbies and needs of people. In addition, the pearl nickel satin coating has fine structure, low porosity, low internal stress, good corrosion resistance, and excellent resistance to scratch and scratch resistance. It has become an important protective decorative coating in Europe and the United States.
In the early 1960s, Europe, the United States, and Japan successively published literature and patents on pearl nickel plating processes and equipment, and various additives developed have also been commercialized. In the late 1980s, China began experimenting and researching in this area. There were few literatures and patents. In particular, the research on additives was basically at the stage of exploration. Most of the products in the production were purchased from foreign companies.
This paper introduces the preparation method of pearl nickel coating and the action mechanism of additives in the process of forming satin gloss coating, and reviews the development status of pearl nickel plating at home and abroad.
2 Preparation method and principle of pearl nickel plating The method for forming the surface of pearl nickel includes mechanical method and electroplating method, and electroplating method can be further divided into composite plating method and emulsifier method.
The mechanical method is to sandblast or blast the substrate to form an uneven surface, and then perform electroplating. The pearl-like satin effect prepared by this method is relatively good, but has the disadvantages of high scrap rate, poor working environment, and high labor intensity, and has been basically eliminated.
The composite plating method is to add non-conductive particles to the base plating solution, and the particles are uniformly dispersed in the plating solution under strong stirring, and co-deposited with nickel, and the particles are embedded in the plating layer to form a nickel composite plating layer [3]. However, due to the pearl-like satin effect and softness of the composite coating is not very satisfactory, it has been basically eliminated.
The emulsifier method is currently the most common method for preparing pearl nickel plating, and it is also the most active research direction. The organic surfactant added to the plating solution can form an emulsion in the plating solution under suitable process conditions, so that the small emulsion droplets are uniformly dispersed in the plating solution. Under the action of the electric field, the positively charged small emulsion droplet moves toward the cathode and is adsorbed at the cathode. The adsorption site is shielded by the droplets of the emulsion, and the metal cannot be deposited, so that the portion forms a recess. The adsorption and desorption processes of the droplets on the surface of the cathode are alternately alternated, and the electrodeposition of the metal on the surface of the electrode is also alternately performed, resulting in the formation of numerous overlapping circular pockets on the surface of the coating layer, according to which The average diameter is different for pearlescent coatings with different effects.
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