| 摘要 |
PROBLEM TO BE SOLVED: To provide a cut steel plate for exhibiting an attractive surface for a long term by preventing corrosion initiated from the cut end. SOLUTION: The cut steel plate has a chemical conversion coating formed directly on the surface of the substrate steel, in which oxide or hydroxide of a valve metal of which the oxide shows high insulation resistance, and fluoride coexists. The cut plate also can employ a plated steel sheet as the substrate steel. In this case, the chemical conversion coating is directly formed on the cut end face in which the substrate steel is exposed without the plated layer. There are Ti, Zr, Hf, V, Nb, Ta, Mo, and W, as valve metals, and one or more of these are employed in combined form. In order to make the self restoration effect by fluoride more effective, it is preferable to adjust a concentration ratio F/O, of F to O, included in the chemical conversion coating so as to be more than 1/100 in an atomic ratio.
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