What Is Black Chrome Plating?
The black chrome plating has loose crystals and a dendritic structure, so it can completely absorb light waves and appear black. It has been proven that with the development and utilization of solar energy, the black chromium coating is the most selective of all black electroplated coatings and coatings. The ratio of the absorptivity a to the reflectivity y of the black chrome coating can be greater than 10, so it is widely used in solar absorbers, weapons, optical instruments and cameras
Black chrome
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- Chinese name
- Black chrome
- Foreign name
- black chromium
- The black chrome plating has loose crystals and a dendritic structure, so it can completely absorb light waves and appear black. It has been proven that with the development and utilization of solar energy, the black chromium coating is the most selective of all black electroplated coatings and coatings. The ratio of the absorptivity a to the reflectivity y of the black chrome coating can be greater than 10, so it is widely used in solar absorbers, weapons, optical instruments and cameras
- Black has a solemn feel and is called a permanent charm. Compared with the black nickel coating, the black chromium coating has better corrosion resistance, durability and selective absorption of solar energy. Although the hardness of black chrome plating is low, HVl30 ~ 350, its wear resistance is similar to that of ordinary chrome plating. Black chrome plating is not pure metallic chromium, but an amorphous oxide crystal. According to analysis, the metal chromium content only accounts for about 50% to 75% of the coating, and the rest is chromium oxide. The oxide mainly exists in the form of chromium trioxide hydrate (Cr203 · xH2O). One example in the literature analyzed the chemical composition of the black chromium coating, and the result was:
- Chromium (Cr) 56.1%, nitrogen (N) 0.4%, carbon (c) 0.1%, hydrogen (H) 1.25%, oxygen (O)> 26.0%
- The black chrome plating has loose crystals and a dendritic structure, so it can completely absorb light waves and appear black. It has been proven that with the development and utilization of solar energy, the black chromium coating is the most selective of all black electroplated coatings and coatings. The ratio of the absorptivity a to the reflectivity y of the black chrome coating can be greater than 10, so it is widely used in solar absorbers, weapons, optical instruments and cameras; due to the more solemn black, it has recently been used in automobiles and daily light industrial products. Decorative parts and other applications are also increasing.
- Except for aluminum, the black chromium coating has a good bond to other common base metals. The black chromium coating has high thermal stability, and its appearance does not change when heated to 480 ° C. Although the corrosion resistance of the black chrome plating is better than that of the ordinary chrome plating, the plating generally requires a base coating of the substrate. Although the black chrome can be directly plated on the copper and brass substrates, this is indeed done; we avoid it Electrochemical corrosion is not counted, and it is not reasonable to do so even from physical considerations; because the thermal expansion coefficient of black chrome plating is very different from that of copper or brass, if the underplating is not used, the black chrome plating will crack and Fall off from the substrate. Therefore, the corrosion resistance of black chromium mainly depends on the quality of the substrate coating. A more reasonable and commonly used underplating layer is a nickel plating layer. Stainless steel is also plated with black chrome, but the surface of stainless steel is severely blunt. Therefore, black chrome plating on stainless steel should first be impact nickel in a high-chloride nickel plating bath. If the black chrome layer has a brighter appearance, If required, a bright nickel layer is required, and then black chrome is plated on the bright nickel layer.
- There are many formulas for black chromium plating, including sodium nitrate, acetic acid, fluoride and vanadate. In recent years, a number of commercial additives have appeared. These additives are mostly combined, which is convenient to add and has good stability.