Steel product excellent in corrosion resistance and corrosion fatigue resistance, and surface treatment method therefor

(19)

(11)

EP 1 743 955 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	24.01.2007 Bulletin 2007/04

(43)	Date of publication A2:
	17.01.2007 Bulletin 2007/03

(21)	Application number: 06014476.3

(22)	Date of filing: 12.07.2006

(51)

International Patent Classification (IPC):

C23C 22/20^(2006.01)

(84)	Designated Contracting States:
	AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR
	Designated Extension States:
	AL BA HR MK YU

(30)

Priority:

15.07.2005 JP 2005206977

(71)	Applicant: NHK SPRING CO., LTD.
	Yokohama-shi, Kanagawa 236-0004 (JP)

(72)	Inventors:
	Suzuki, Takeshi Yokohama-shi Kanagawa 236-0004 (JP) Ono, Yoshiki Yokohama-shi Kanagawa 236-0004 (JP) Ikai, Kazuya Yokohama-shi Kanagawa 236-0004 (JP)

(74)	Representative: Zech, Stefan Markus et al
	Meissner, Bolte & Partner Widenmayerstrasse 48 80538 München 80538 München (DE)

(54)	Steel product excellent in corrosion resistance and corrosion fatigue resistance, and surface treatment method therefor

(57) The invention provides a steel product excellent in corrosion resistance and corrosion fatigue resistance, comprising a coating film on the surface of the steel product, wherein a ratio of the number of Al atoms to the total number of Fe, C, Al, P and O atoms and optionally added Si, Mn and Cr atoms is 0.5% or more in an average composition of the coating film, and the number of Al atoms in the average composition of the coating film is higher than the number of Al atoms in an average composition of the steel product before surface treatment.

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