Black chrome for solar collectors

Journal Article · Sun Oct 01 04:00:00 EDT 1978 · Met. Finish.; (United States)

OSTI ID:6112563

Cathro, K J

A tetrachromate bath utilized for the electrodeposition of black chrome as a selective surface on nickel plated mild steel significantly reduced plating time. Experiments were conducted with the tetrachromate bath consisting of 400 g/L of chromic acid, 60 g/L of sodium hydroxide, 7.5 g/L of barium carbonate for sulfate removal, 2.5 g/L of sucrose to produce trivalent chrome, and 0.5 g/L fluosilicic acid. The mild steel plates were degreased in trichloroethylene, dried and derusted with 10 wt/vol citric acid for 2 min, rinsed and immersed in alkaline solution for 10 min, rinsed and nickel-plated at 3.5 A for 10 min, and rinsed and plated in the black chrome bath at 10 A and 20/sup 0/C. Tests were also performed in which the electrolysis time, current density, solution composition, temperature, substrate, and anode material were varied. Solar absorptance of the black chrome surface was within the 0.97 range and the thermal emittance was within the 0.1-0.2 range. Increasing the concentration of fluosilicic acid in the bath to 1.0 g/L improved deposition uniformity, suitable optical properties were obtained with a charge current in the range 10-20 C/sq cm and a current density ranging 1000-3000 A/sq m. The deposits were stable in the air temperatures of 200/sup 0/C and vacuum temperatures to 300/sup 0/C, little degradation was observed after the plates were exposed to solar radiation for 12 months under stagnation conditions. The deposits obtained were comparable to those achieved with other plating baths tested.

• OSTI ID: 6112563
• Journal Information: Met. Finish.; (United States), Journal Name: Met. Finish.; (United States) Vol. 76:10; ISSN MEFIA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
ABSORPTIVITY
BLACK CHROME
BLACK COATINGS
CHROMATES
CHROMIUM
CHROMIUM COMPOUNDS
COATINGS
CURRENT DENSITY
DEPOSITION
ELECTRODEPOSITION
ELECTROLYSIS
ELEMENTS
EMISSIVITY
LYSIS
METALS
OPTICAL PROPERTIES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SOLAR ABSORBERS
SOLAR COLLECTORS
SPECTRALLY SELECTIVE SURFACES
SUBSTRATES
SURFACE COATING
SURFACE PROPERTIES
SURFACES
THERMAL DEGRADATION
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS