Hans Zeilinger

Development of Protective Coatings to Reduce Hydrogen and Tritium Permeation

An important demand with respect to the operability of a nuclear process heat system, such as the prototype plant for nuclear process heat, is the complete retention of tritium. A significant contr...

Selection of a black chrome bath for continuous tube-plating and the properties of the coatings deposited from it

Abstract The planning and design of a 50-kW experimental solar thermal power plant which was to have a selective coating on the absorber initiated an investigation into black chrome deposition in order to find the most suitable type of solution for a continuous plating process. Acetic acid-type and fluorosilic acid-type electrolytes were tested with a variety of additives and deposition parameters. The best results were achieved with an electrolyte containing fluorosilic acid as the catalyst. With this solution, coatings with optimum thermo-optical properties were formed in only 22 sec at current densities of 0.5 A cm−2 and a temperature of 15°C. These yielded values of 0.97 for total absorptance (AM2 spectrum) and 0.08 (100°C) for the thermal emittance on a basis of light Watts-type nickel. Other nickel undercoatings which were investigated produced less satisfactory results. Both the thermal stability of the plating up to temperatures of 400°C and the dependence of its IR emittance on temperature were investigated. The tubes coated in the way described have a uniform, matt-black appearance and the thermo-optical properties are constant along their whole length and round their whole circumference.