Nippon Steel Corporation

Hiroaki Uramoto

Kiyokazu Ishizuka

Noriyuki Maekawa

Kenichiro Matsumura

Masahiro Fuda

Hidetoshi Shindo

Ikuo Kikuchi

Ikuro Yamaoka

Fumio Shibao

Takashi Futaba

Keita Katsumaru

A plated steel includes: a steel; a zinc based electroplated layer formed on a surface of the steel; and an organic resin coating layer formed on a surface of the zinc based electroplated layer, in which the surface of the zinc based electroplated layer has hairline extending in a predetermined direction, Ra (ML) measured on the surface of the zinc based electroplated layer is 0.10 to 0.70 &#x3bc;m, on the surface of the zinc based electroplated layer, a peak number PPI measured in a hairline orthogonal direction with a reference level of 10 &#x3bc;inch satisfies PPI&#x2265;350&#xd7;Ra (MC) with respect to Ra (MC), on a surface of the organic resin coating layer, Ra (CC) satisfies Ra (CC)/Ra (CL)&#x2265;1.10 with respect to Ra (CL), and Ra (CC) satisfies Ra (CC)&#x3c;Ra (MC) with respect to Ra (MC).

Plated steel

Provided is a surface treated steel sheet for a fuel tank, the surface treated steel sheet including: a Zn plated layer or a Zn&#x2014;Ni alloy plated layer which is formed on at least a surface of the steel sheet to be an inner surface of the fuel tank; and a chromate-free chemical conversion coating layer containing a water-and-oil repellent, the chromate-free chemical conversion coating layer being placed over the Zn plated layer or the Zn&#x2014;Ni alloy plated layer on the surface to be the inner surface of the fuel tank. A water contact angle on a surface of the chromate-free chemical conversion coating layer is more than or equal to 70 degrees and an n-hexadecane contact angle on the surface of the chromate-free chemical conversion coating layer is more than or equal to 30 degrees and less than or equal to 70 degrees.

Surface treated steel sheet for fuel tank

A steel sheet for a fuel tank according to the present invention includes: a Zn&#x2014;Ni alloy plated layer placed on one surface or each of both surfaces of a base metal; and a chromate-free chemical conversion coating film which is placed over the Zn&#x2014;Ni alloy plated layer. The Zn&#x2014;Ni alloy plated layer has a crack starting from an interface with the chromate-free chemical conversion coating film and reaching an interface with the steel sheet, the chromate-free chemical conversion coating film consists of an organosilicon compound consisting of a condensation polymer of a silane coupling agent, a phosphoric acid compound and/or a phosphonic acid compound, a vanadium compound, and a titanium compound and/or a zirconium compound, and a concentration of a total of amounts in terms of metal, per surface, of the phosphoric acid compound and/or the phosphonic acid compound+the vanadium compound+the titanium compound and/or the zirconium compound, is 5 mass % to 20 mass %.

Steel sheet for a fuel tank

A steel sheet for a fuel tank includes: a Zn&#x2014;Ni alloy plated layer which is placed on one surface or each of both surfaces of a base metal and formed on at least one surface; and an inorganic chromate-free chemical conversion coating film which is placed over the Zn&#x2014;Ni alloy plated layer. The Zn&#x2014;Ni alloy plated layer has a crack starting from an interface between the Zn&#x2014;Ni alloy plated layer and the inorganic chromate-free chemical conversion coating film and reaching an interface between the Zn&#x2014;Ni alloy plated layer and the steel sheet, and a water contact angle on a surface of the inorganic chromate-free chemical conversion coating film is more than or equal to 50 degrees.

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Tokyo, Japan

Hiroaki Uramoto