After electroless nickel plating, in addition to heat treatment such as baking and hydrogen removing to enhance electroless nickel plating performance, various subsequent surface treatments can be performed to give higher corrosion resistance, wear resistance and other surface functions.
Chromate after plating passivation
After cleaning the electroless nickel layer immersed in a dilute aqueous solution of chromic anhydride (CrO3, 1-10%) for several minutes, remove the wash and dry, the corrosion resistance of the coating is improved. Some products of chromic acid solution also contains filming agent, wetting agent and other additives. In addition to the role of passivation, but also both the role of the closure of the film, so to improve the electroless nickel layer anti-discoloration and corrosion resistance of the effect is obvious.
Plating anodic coating
In the high-phosphorus electroless nickel layer and then coated with a thin layer of lower phosphorus chemical nickel layer, the formation of double-layer electroless nickel structure. As the surface of low phosphorus electroless nickel electrode potential is lower, sacrificial anode sacrificial layer, significantly improve the corrosion resistance of plating. Similarly, in order to improve the long-term anti-corrosion performance plating, electroless nickel plating covered with zinc, cadmium or other sacrificial anode alloy surface layer. Even after zinc and cadmium plating, the heat treatment at a higher temperature is performed to improve the ductility of the plating layer, and the diffusion layer can be formed in the interface region of different metal layers. Practical results show that the use of this post-treatment technology, the steel parts of the anti-atmospheric corrosion of the ocean increased about 10 times.
Surface functional post-processing
A thin layer (1-3 microns) of high coercivity magnetic material, such as a cobalt-based alloy, is vacuum sputter deposited on the surface of the non-magnetic electroless nickel layer to form a high performance magnetic recording device. Computer hard disk manufacturing process is to adopt this technical specification.
High-density printed circuit surface selective electroless nickel plating, and then immersed in the electroless nickel surface gold or electroless gold plating 0.3-0.8 microns, will greatly improve the surface electrical connectivity.
Electroless nickel plating Surface conversion film formed in dilute nitric acid or some special oxidizing medium. It has good optical absorption and emission characteristics. It is called "super black film" and is especially suitable for solar energy absorbing devices.
Article from NdFeB Industry Network