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Black chromium plating

Black chromium plating, which would be used for decorative purposes, has recently been used for solar collectors as selective light absorbing functional plating. Ideal light selective absorption films excel with increasing absorptance (α) in the solar wavelength region (0.3 - 2.5μm) and decreasing emissivity (ε) in the infrared wavelength region (3.0μm or more).
Type of plating Features (characteristic value)
Black chromium plating
(1) Sargent bath
- Film composition: CrOx-Cr
- Optimum plating thickness: 180nm
- Primary plating: Nickel plating
- Absorptance of light (α): 0.96; Emissivity of light [ε(t°C): 0.1 at 100°C]
- Thermal stability: 350°C
(2) Trivalent chromium bathGreen mark - Film composition: Cr-Co
- Optimum plating thickness: 180nm
- Primary plating: Nickel plating
- Absorptance of light (α): 0.96; Emissivity of light [ε(t°C): 0.10 at 100°C]
- Thermal stability: 200°C

(From “Kino Mekki Himaku no Bussei” edited by Denki Mekki Kenkyukai, Nikkan Kogyo Shimbun Ltd.)

Adoption examples
Black chromium plating
Black-chromium-plated solar collector
(From “Denki Mekki Gaido” edited by Federation
of Electro Plating Industry Association, Japan)
- The absorptance (α) and emissivity (ε) of light are measured by using spectrophotometer with an integrating sphere.