BLACK CHROMIUM PLATING BATH USEFUL FOR SOLAR SELECTIVE COATINGS

摘要

The composition disclosed is an improved black chromium plating bath useful, for example, for solar selective coatings. The bath comprises an aqueous solution of sulphate-free chromic acid containing nitrate, borate and fluorosilicate ions. Such a bath can be employed at room temperature or higher e.g. in the temperature range 30.degree.C to 50.degree.C and at a low current density e.g. 0.07 to 0.28 A cm2,to obtain a good quality black chromium deposit which is quite coherent and has a high absorptivity to emissivity ratio e.g. about 8 .