Watt nickel (nickel sulfide) modified by electroplating on electric heating tubes

Watt nickel (nickel sulfide) modified by electroplating on electric heating tubes

Modified Watt nickel formula, using nickel sulfate, along with the addition of nickel bromide or nickel chloride. Due to internal stress, nickel bromide is mostly used. It can produce a semi bright, slightly stressed, and ductile coating; And this coating is easily activated for subsequent electroplating, with relatively low cost.

4. The role of each component in the plating solution:

The main salts - nickel sulfamate and nickel sulfate are the main salts in the nickel solution. Nickel salts mainly provide nickel metal ions required for nickel plating and also act as conductive salts. The concentration of nickel plating solution varies slightly with different suppliers, and the allowable content of nickel salts varies greatly. The nickel salt content is high, which allows for the use of high cathode current density and fast deposition speed. It is commonly used for high-speed thick nickel plating. However, if the concentration is too high, it will reduce cathodic polarization, have poor dispersion ability, and cause significant loss of the plating solution. The nickel salt content is low, the deposition rate is low, but the dispersion ability is good, and a crystalline and bright coating can be obtained.

Buffer - Boric acid is used as a buffer to maintain the pH value of the nickel plating solution within a certain range. Practice has shown that when the pH value of nickel plating solution is too low, it will lead to a decrease in cathode current efficiency; When the pH value is too high, due to the continuous precipitation of H2, the pH value of the liquid layer near the cathode surface rapidly increases, leading to the generation of Ni (OH) 2 colloid. The inclusion of Ni (OH) 2 in the coating increases the brittleness of the coating. At the same time, the adsorption of Ni (OH) 2 colloid on the electrode surface also causes the retention of hydrogen bubbles on the electrode surface, resulting in an increase in the porosity of the coating. Boric acid not only has a pH buffering effect, but also enhances cathodic polarization, thereby improving the performance of the plating solution and reducing the phenomenon of "burning" at high current densities. The presence of boric acid is also beneficial for improving the mechanical properties of the coating.

Anode Activator - Except for the use of insoluble anodes in sulfate type nickel plating solutions, all other types of nickel plating processes use soluble anodes. The nickel anode is prone to passivation during the electrification process. In order to ensure the normal dissolution of the anode, a certain amount of anode activator is added to the plating solution. Through experiments, it was found that CI chloride ion is the best nickel anode activator. In nickel plating solution containing nickel chloride, nickel chloride not only serves as the main salt and conductive salt, but also acts as an anode activator. In electroplating nickel solutions that do not contain nickel chloride or have a lower content, a certain amount of sodium chloride needs to be added according to the actual situation. Nickel bromide or nickel chloride is also commonly used as a stress relieving agent to maintain the internal stress of the coating and give the coating a semi bright appearance.

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