General characteristics and types of chrome plating
Characteristics of chrome plating
1. Chrome plating uses oxo acid as the main salt, chromium and oxygen have strong affinity, electrolysis is difficult, and current efficiency is low;
2. Although the polarization value of chromium plating is large, the polarization degree is very small, so the dispersion and coverage of the plating solution are very poor, and auxiliary anodes and protective cathodes are often used;
3. Chromium plating requires a large current density, and the current efficiency is very low, and a large amount of hydrogen is precipitated, resulting in a large drop in the ohmic voltage of the plating solution, so the voltage of chrome plating is relatively high;
Types of chrome plating
1. Protection-decorative chrome plating
Protection—Decorative chrome plating, commonly known as decorative chrome. It has the dual functions of anti-corrosion and appearance decoration.
2. Hard chrome (wear-resistant chrome, industrial chrome plating)
The chromium coating deposited under certain conditions has high hardness and wear resistance. The Vickers hardness of hard chromium reaches 900～1200kg/mm2. Chromium is the highest hardness coating in the common coating, which can improve the wear resistance of the parts and extend Service life.
3. Milky white chrome coating
The coating has good toughness, low hardness, less porosity, less cracks, soft color and good matting performance. It is often used for chrome plating of measuring tools, index plates, instrument panels, etc.
Adding bright wear-resistant chromium to opalescent chromium is called double-layer chromium plating. It is widely used in aircraft, ship parts and gun cavity.
4. Loose hole chrome plating
Loose hole chrome plating is applied to sliding friction parts under heavy pressure and heat-resistant, corrosion-resistant and wear-resistant parts, such as internal cavity of internal combustion engine cylinder and piston ring.
5. Black chrome
In chromium plating that contains no sulfate and contains a catalyst, a pure black chromium layer can be plated, with chromium oxide as the main component, so it has excellent corrosion resistance and extinction performance, and is used in aviation, optical instruments, solar absorption panels and daily necessities. Protection-decoration.