CN-121992469-A - Stainless steel material for separator of fuel cell and method for producing same

Abstract

The present invention relates to a stainless steel material for a separator of a fuel cell, wherein the stainless steel material has an intensity ratio of F － /Fe 2 － of 10 or more and a depth of 5nm or more and an intensity ratio of CrO 3 － /Fe 2 － of 1 or more and a depth of 6nm to 14nm as a result of depth analysis of ion intensities of F － 、CrO 3 － and Fe 2 － measured by time-of-flight secondary ion mass spectrometry, and a method for producing the same.

Inventors

• ISHIKAWA YUZO
• Shan Qixiu
• Kazuhei Kikuchi
• S. Fujimoto Fujimoto
• IKAWA YASUHIRO
• YAGI YUSUKE

Assignees

• 丰田自动车株式会社
• 日本金属株式会社

Dates

Publication Date

20260508

Application Date

20251027

Priority Date

20241101

Claims (3)

1. 1. A stainless steel material for the separator of fuel cell, For the results of the deep resolution of the F － 、CrO 3 － and Fe 2 － ion intensities as determined by time of flight secondary ion mass spectrometry, An intensity ratio of F － /Fe 2 － of 10 or more, a depth of 5nm or more, and The CrO 3 － /Fe 2 － has an intensity ratio of 1 or more and a depth of 6nm to 14 nm.
2. 2. The stainless steel material according to claim 1, wherein the depth of the F － /Fe 2 － is 14.0nm or less, with an intensity ratio of 10 or more.
3. 3. A method for producing a stainless steel material for a separator of a fuel cell, comprising (i) a step of applying a conductive passivation film to a stainless steel substrate, (I) The process of (1) comprises the following steps: (A) A step of injecting fluorine into the passivation film, (B) A step of modifying the passivation film in an alkaline aqueous solution or a nonaqueous solvent, and (C) A step of eluting iron in the passivation film, (A) The process comprises the pulse electrolysis treatment of stainless steel in an aqueous solution containing fluoride ions, (A) The pulsed electrolytic treatment of the step includes electrolytic treatment under conditions of an anode current density of 0.05A/dm 2 ～1.0A/dm 2 and a cathode current density of 0.05A/dm 2 ～5.0A/dm 2 and an electrolytic time of 10 seconds to 10 minutes, (B) The process comprises a pulsed electrolytic treatment of a stainless steel substrate in an aqueous alkaline or nonaqueous solvent.

Description

Stainless steel material for separator of fuel cell and method for producing same Technical Field The present invention relates to a stainless steel material for a separator of a fuel cell and a method for manufacturing the same. Background The fuel cell has a stack structure in which a predetermined number of unit cells generating electromotive force by a reaction between a fuel gas (hydrogen) and an oxidizing gas (oxygen) are stacked. The unit cell includes a membrane electrode assembly having anode and cathode electrode layers (a catalyst layer and a gas diffusion layer) on both surfaces of an electrolyte membrane, and separators disposed on both surfaces of the membrane electrode assembly. The separator for a fuel cell has a function of electrically connecting the unit cells in series and a function as a partition wall that blocks the fuel gas, the oxidant gas, and the coolant from each other. Various studies have been made on such a separator for a fuel cell. For example, japanese patent application laid-open No. 2008-277146 discloses a stainless steel conductive member, wherein the Cr/Fe ratio (atomic%) in a passivation film analyzed by surface X-ray photoelectron spectroscopy (XPS) is 3 or more, the F concentration in the passivation film analyzed by surface X-ray photoelectron spectroscopy (XPS) is 0.1 atomic% or more, and the Li concentration in the passivation film analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0.01 atomic% or more. Japanese patent application laid-open No. 2010-140886 discloses a stainless steel material for a separator of a solid polymer fuel cell, which is characterized by comprising a stainless steel base material, an oxide film provided on the surface of the stainless steel base material, a conductive layer provided on the surface of the oxide film and having a nonmetallic conductive substance, and a conductive substance provided so as to pass through the oxide film and electrically connected to the stainless steel base material and the conductive layer, wherein the nonmetallic conductive substance provided on the surface of the oxide film contains graphitic carbon, and when the peak intensities of diffraction lines of atomic planes obtained by measuring the crystals of the graphitic carbon by wide angle X-ray diffraction are compared, the ratio of the peak intensities of diffraction lines of (110) atomic planes to the peak intensities of diffraction lines of (004) atomic planes is less than 0.1. Japanese patent application laid-open No. 2022-45138 discloses a fuel cell separator comprising a metal base material, a corrosion-resistant metal intermediate layer formed on the metal base material, and a carbon layer formed on the corrosion-resistant metal intermediate layer, wherein the intensity ratio (I D/IG) of the peak intensity (I D) of the D band to the peak intensity (I G) of the G band in the raman spectrum of the carbon layer is 0.70 or more and less than 0.95. Disclosure of Invention Since the separator for a fuel cell (also simply referred to as a "separator") also plays a role of allowing generated current to flow into adjacent cells, a substrate constituting the separator is required to have high conductivity and sufficient corrosion resistance that can be maintained for a long period of time in a high-temperature acid atmosphere inside the cells of the fuel cell. Here, high conductivity means low contact resistance. In addition, the contact resistance means that voltage drop occurs between the electrode and the separator surface due to an interface phenomenon. Therefore, as a base material constituting the separator, pure titanium or titanium alloy excellent in conductivity and corrosion resistance is often used, which is one of important factors leading to an increase in cost in the manufacture of the separator. Therefore, in order to reduce the cost, it is attempted to use a low-cost base material such as stainless steel as a base material and form a layer imparting conductivity and corrosion resistance on the surface of the base material, thereby manufacturing a separator having conductivity and corrosion resistance. The layer imparting conductivity and corrosion resistance to stainless steel is formed by, for example, physical vapor deposition (PhysicalVaporDeposition: PVD). However, such PVD processing requires a process in vacuum, and requires a plurality of steps as film forming steps. Accordingly, the present invention provides a stainless steel material for a separator of a fuel cell having sufficient corrosion resistance and low contact resistance, and a method of manufacturing the stainless steel material. The present inventors have made various studies on means for solving the above problems, and as a result, have found that a coating film (conductive passivation coating film) to which conductivity is imparted is formed on the surface of a stainless steel substrate so that the depth of the F －、CrO3－ and Fe 2－ ion intensities mea