Preparation Of The Satin Nickel Electro-deposition And Study On The Additives Of The Satin Nickel Electro-deposition

The satin nickel coating is an excellent ornamental coating owing to its soft luster appearance, low body stress and good wear resistance, and it has been applied to the decorative parts in automobile, electronic product and commodity metal.In the text the ingredients of additives of the decorative satin nickel electro-deposition have been ascertained through a large quantity of experiments. According to the different function in the electroplating bath the additives have been divided into three components which are the carrier additives, the assistant additives and the satin finish additives. The carrier additives is composed of basic brighter of nickel coating, the main function of which is to reduce the crystalloid size of nickel coating, to make the nickel coating appear certain brightness, to reduce the stress and to improve the tractility of nickel coating as well. The assistant additives are sodium allylsulfonate and sodium unsaturated alkylsulfonate, the function of which is to expand technological current density range. The satin finish additives are the most important to the appearance of the satin nickel electroplating. In the text two kinds of the satin finish additives are studied. With each kind of the satin finish additives in the electroplating bath an even satin-finished nickel was achieved. One of the satin finish additives contains a sulfosuccinic acid anion surfactant, a carboxylic ion anion surfactant and one quaternary ammonium cathode surfactant, which did not contain nonionic surfactant. The other contains a nonionic surfactant and a specific surfactant. With the satin finish additives in the electroplating bath the small emulsified drops are produced. During the nickel depositing the small emulsified drops are absorbed on the surface of the cathode and prevent nickel ion depositing. Then the pits are formed on the surface of the cathode.In the text the effects of technological parameters on the coating appearance have been researched,including content of additive, temperature and pH of the bath, current density etc. Using the SEM techniques a lot of round pits were observed on the surface of satin nickel coating. Because of the pits the diffuse reflection occurred under the light and the satin appearance was obtained. The results of polarization curves show that the corrosion resistance of the satin nickel coating is more favorable than semi-bright nickel. The result of adhesive force test shows that the adhesive force between the coating and the substrate is excellent.Using small trough experiments the time to achieve satin finish appearance and the stability of electroplating bath were tested. The results showed that the satin nickel coating could be obtained in 3 minutes to 4 minutes and the electroplating bath could last for about 15 hours. Without active carbon treating after using, the electroplating bath could be used again with adding suitable quantity of additives after the normal filtrating.