- Oct 12, 2018 -
The black plating process is also a popular decorative plating process after the imitation gold plating process. A conventional black coating is black nickel, a nickel-zinc alloy coating.
In recent years, nickel-tin has become more and more widely used as the main black coating, and is often called gun color coating or pearl black.
They are used for the appearance decoration of optical instruments, military products, light industry, daily hardware products, and functional applications such as matting and heat absorption.
Both of these coatings are thin and do not have a good anti-corrosion effect on the substrate. They should be plated with intermediate coatings such as copper and nickel to improve their appearance and corrosion resistance. After plating, it is often oiled or coated with an organic coating to protect it.
During the electroplating process, sulfur and nickel in the thiocyanate ion form a black NiS. Because the current density is very low, the obtained coating is brittle, so it is impossible to plate too thick, and the brightness of the coating is completely dependent on the bright effect of the bottom plating. The brighter the bottom plating layer, the blacker the black nickel layer, otherwise the blackness is lowered.
The pearl black electroplating process is divided into cyanide and cyanide-free. The cyanide plating solution is relatively stable and the black color is relatively uniform; if the complexing agent without the cyanide plating solution is properly selected, a good effect can be obtained.