| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface-treated steel sheet which has excellent corrosion resistance and resistance to black spot rust and is also excellent in electromagnetic wave shielding properties (electrical conductivity).SOLUTION: Both of a discontinuous covering layer (A) which has electrical conductivity and comprises a chromium-free substance, and a chromium-free organic and/or inorganic film (B) are formed successively from below on the surface of a galvanized steel sheet or an aluminum-plated steel sheet to obtain the surface-treated steel sheet. The surface-treated steel sheet has ≥2 spots, each of which has 0.5-50% coverage of the surface of the steel sheet with the covering layer (A) and ≤0.01 μm average thickness of the film (B) existing on the covering layer (A), per 100 μm visual field when the optional cross section of the surface-treated steel sheet is observed in the thickness direction. |
