PURPOSE: To form an absorbing surface hardly receiving stress corrosion and having good heat collecting efficiency of solar energy by a method wherein a surface of a ferrite type stainless steel subjected to predetermined finishing treatment containing a specific amount of Nb and Mo is adjusted to a surface with specific surface roughness and, subsequently, black coloring is applied.
CONSTITUTION: Surface adjustment is applied to a surface of a ferrite type stainless steel containing 0.2W1.0wt% Nb and 1W3wt% Mo and being subjected to surface finishing of BA finish or more so as to adjust surface roughness thereof to 0.2W 0.1μ. The surface adjustment is carried out by anodic electrolytic treatment or mechanical polishing treatment. Subsequently, for example, said treated stainless steel is immersed in a chromic acid-sulfuric acid aqueous solution to apply black coloring to said surface of the ferrite type stainless steel by an acidic blackening oxidation process or the like carrying out blackening oxidation. Thereby, a selective absorbing surface of solar energy with excellent spectrometric characteristics can be prepared.
TAKATSU KIYOSHI
INOUE TAKASHI
