[Problem] Provided are a protective-layer-coated-interconnector, a cell stack, and a hydrogen energy system. A component (particularly Cr) of the interconnector is prevented from diffusing even if the interconnector is exposed to high temperature for a long time. The interconnector has sufficient diffusion barrier performance and protective performance even with a protective layer thinner than conventionally, is inhibited from being degraded through use, and has excellent electrical conductivity.

[Solution] A protective-layer-coated-interconnector including an interconnector material and a protective layer on the surface of the interconnector material, wherein the protective layer contains a metal layer constituted by a Group 11 element. A cell stack and a hydrogen energy system that each include this interconnector.

The disclosure provides an anti-corrosion conductive film and methods of making and using thereof. The anti-corrosion conductive film is formed by sequentially forming an anti-corrosion protective layer, a stress transition layer and a conducting layer on the surface of a substrate by deposition through a high-low pulse bias alternation method. The anti-corrosion conductive film is a nano-multilayer anti-corrosion conductive film exhibiting excellent corrosion resistance and conductivity. The anti-corrosion conductive film has great application prospects in the fields of metal polar plates of fuel cells, ground grid equipment of power transmission lines, and the like.

An interconnector for a solid-oxide electrochemical cell stack of the embodiment includes: a metal base containing an iron-based alloy containing chromium; and a protective film provided on a surface of the metal base. The protective film includes a protective film body containing at least one selected from a spinel oxide and a perovskite oxide, and dispersed phases scattered in the protective film body and containing an oxide of at least one element selected from the group consisting of rare earth elements and zirconium.

Disclosed is a stainless steel having excellent surface electrical conductivity for a fuel cell separator. According to an embodiment of the disclosed stainless steel having excellent surface electrical conductivity for a fuel cell separator, a value of the following surface oxide atomic ratio (1) may be 0.08 or more, as measured on the surface of a stainless steel containing 15 wt % or more of Cr by X-ray angle-resolved photoemission spectroscopy using an Al-Kα X-ray source under the condition where a take-off angle of photoelectrons is from 12° to 85°.

[00001]$\begin{array}{cc}\frac{\mathrm{sum}\mathrm{of}\mathrm{atomic}\mathrm{concentrations}\left(\mathrm{at}\%\right)\mathrm{of}\mathrm{Cr}\mathrm{in}\mathrm{Cr}\mathrm{hydroxide}}{\begin{array}{c}\mathrm{sum}\mathrm{of}\mathrm{atomic}\mathrm{concentrations}\left(\mathrm{at}\%\right)\mathrm{of}\mathrm{metal}\mathrm{elements}\\ \mathrm{in}\mathrm{total}\mathrm{oxides}\mathrm{and}\mathrm{hydroxides}\end{array}}& \left(1\right)\end{array}$

The Cr hydroxide represents CrOOH, Cr(OH).sub.2, or Cr(OH).sub.3. The total oxides and hydroxides include a Cr oxide, the Cr hydroxide, an Fe oxide, an Fe hydroxide, and a metal oxide (MO), and the metal oxide (MO) includes a mixed oxide, wherein M represents an alloying element other than Cr and Fe or a combination thereof in a matrix, and O represents oxygen.

A conductive member includes a base material and a covering part located on the base material and containing a first element. The base material contains chromium. The first element has a smaller value of first ionization energy and a smaller absolute value of free energy formation of oxide than chromium.

A metal support for an electrochemical element where the metal support includes a plate face, has a plate shape as a whole, and has a warping degree of 1.5×10.sup.−2 or less determined by calculating a least square value through the least squares method using at least three points in the plate face of the metal support, calculating a first difference between the least square value and a positive-side maximum displacement value on a positive side with respect to the least square value and a second difference between the least square value and a negative-side maximum displacement value on a negative side that is opposite to the positive side with respect to the least square value, and dividing the sum of the first difference and the second difference by a maximum length of the plate face of the metal support that passes through a center of gravity.

There is provided a metal member capable of effectively preventing a coating layer from peeling off from a base. The metal member in an embodiment is a metal member that is used in a solid-oxide type electrochemical stack, and includes: a base formed of ferritic stainless steel; and a metal film provided on the base, in which the metal film includes a first metal layer containing Co and a second metal layer made of Mn, and is a stack in which the first metal layer and the second metal layer are sequentially stacked from the side of the base.

There is provided a metal member capable of effectively preventing a coating layer from peeling off from a base. The metal member in an embodiment is a metal member that is used in a solid-oxide type electrochemical stack, and includes: a base formed of ferritic stainless steel; and a metal film provided on the base, in which the metal film includes a first metal layer containing Co and a second metal layer made of Mn, and is a stack in which the first metal layer and the second metal layer are sequentially stacked from the side of the base.

A production method for a stainless steel sheet for fuel cell separators comprises: preparing a stainless steel sheet as a material; thereafter removing an oxide layer at a surface of the stainless steel sheet; and thereafter subjecting the stainless steel sheet to electrolytic etching treatment in an active region of the stainless steel sheet.

A production method for a stainless steel sheet for fuel cell separators comprises: preparing a stainless steel sheet as a material; thereafter removing an oxide layer at a surface of the stainless steel sheet; and thereafter subjecting the stainless steel sheet to electrolytic etching treatment in an active region of the stainless steel sheet.