Electroless nickel plating is a process in which a nickel layer is deposited on the surface of a material without an impressed current. The main purposes of heat treatment after electroless nickel plating are as follows:
1. Improve adhesion: Although the electroless nickel plating process can obtain good adhesion between the coating and the substrate, appropriate heat treatment can further improve the adhesion between the coating and the substrate. During the heat treatment process, some degree of diffusion and bonding may occur between the coating and the substrate, making the interface bond more firm.
2. Release internal stress: In the process of electroless nickel plating, internal stress may occur in the coating due to the non-uniformity of the chemical reaction and fluctuations in temperature and concentration. These internal stresses can cause deformation or cracking of the coating. By heat treatment, the internal stress of the coating can be redistributed and released, reducing the risk of cracking and spalling.
3. Improve corrosion resistance and hardness: Heat treatment of the electroless nickel plating layer can adjust the crystal structure of the coating, improve the hardness of the coating, and thus improve the wear resistance. At the same time, heat treatment can also improve the corrosion resistance of the coating, because through heat treatment can reduce the porosity of the coating, make the coating more dense, and enhance the blocking ability of the corrosive medium.
4. Uniform coating composition: The electroless plating solution contains a variety of chemicals, which may lead to local enrichment of some elements in the coating. The heat treatment can promote the diffusion and homogenization of these elements in the coating, so as to obtain uniform coating properties.
5. Enhance special properties: Some special electroless nickel plating processes, such as nickel coatings containing boron or phosphorus, may require heat treatment to stimulate their special physical or chemical properties, such as improving hardness, temperature resistance or catalytic performance.
Generally, after the use of Bigely electroless nickel solution, the temperature range is controlled from 200°C to 400°C, and the heat treatment time is determined according to the thickness of the coating, the type of substrate and the desired properties. In order to ensure the effect of heat treatment, the heat treatment parameters must be optimized according to the specific workpiece material, coating properties and application requirements.
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