Stainless steel, titanium, or titanium alloy solid polymer fuel cell separator and its method of production and method of evaluation of warp and twist of separator
View Patent ↗The present invention releases a method of producing a metal separator for a solid polymer fuel cell by stainless steel, titanium, or titanium alloy during which securing lower cost and mass producibility by using a material having a high workability to form a complicated shape by a high productivity, then using an inexpensive blast process to drive a conductive substance into the surface of the metal separator member, that is, provides a stainless steel, titanium, or titanium alloy solid polymer fuel cell separator comprised of stainless steel, titanium, or titanium alloy in the surface of which a low ion release conductive substance is buried, having an arithmetic mean roughness (Ra) of the separator surface of 0.5 to 5.0 μm, having a 10-point mean roughness (Rz) of 3 to 20 μm, having an average spacing of surface relief shapes (Sm) of 300 μm or less, having values of a warp rate and twist rate of a separator of 0.1 or less, and having a contact resistance value with respect to carbon paper of 15 mΩcm 2 or less at a surface pressure of 1 MPa.
1. A solid polymer fuel cell separator comprised of stainless steel, titanium, or a titanium alloy at part or all of the surface of which a low ion release conductive substance is buried,
said solid polymer fuel cell separator characterized in that
said separator surface has an arithmetic mean roughness (Ra) of 0.5 to 5.0 μm, a 10-point mean roughness (Rz) of 3 to 20 μm, and an average spacing of surface relief shapes (Sm) of 300 μm or less,
at predetermined positions near the four corners of said separator, when an origin is O, placing L near a corner in a rolling direction of the sheet from the origin O, C near a corner in a direction vertical to rolling direction from the origin O, and X near a corner in a diagonal direction from the origin O, a length of a line segment between OL is LL, a length of an OC line segment is LC, a length between OX is LX, a maximum strain height from the line OL to the center plane in a thickness direction of the separator is HL1, one from the line CX is HL2, from the line OC is HC1, from the line LX is HC2, one from the line OX is HXC, and a distance between point X and a plane formed by points O, L, and C is HXT, the values of warp rates W L1 , W L2 , W C1 , W C2 , and W XC defined by equation <1> to equation <5> and the values of twist rates T XL and T XC defined by equation <6> to equation <7> are 0.1 or less, and, the contact resistance value with respect to carbon paper is 15 mΩcm 2 or less at a surface pressure of 1 MPa:
Front
side
L
direction
warp
rate
:
W
L
1
=
HL
1
LL
〈
1
〉
Back
side
L
direction
warp
rate
:
W
L
2
=
HL
2
LL
〈
2
〉
Left
side
C
direction
warp
rate
:
W
C
1
=
HC
1
LC
〈
3
〉
Right
side
C
direction
warp
rate
:
W
C
2
=
HC
2
LC
〈
4
〉
Diagonal
direction
warp
rate
:
W
XC
=
HXC
LX
〈
5
〉
L
direction
length
reference
twist
rate
:
T
XL
=
HXT
LL
〈
6
〉
C
direction
length
reference
twist
rate
:
T
XC
=
HXT
LC
.
〈
7
〉
2. A solid polymer fuel cell separator as set forth in claim 1 , wherein said low ion release conductive substance contains at least one of Au, WC, or WB and a balance of unavoidable impurities.
3. A solid polymer fuel cell separator as set forth in claim 1 , wherein said low ion release conductive substance contains TaN or TaN and at least one of WC and WB mixed together and a balance of unavoidable impurities.
4. A solid polymer fuel cell separator as set forth in claim 2 , containing as said unavoidable impurities at least one of Co, Cr, Ni, Fe, Cu, and Sn at the surface of said solid polymer fuel cell separator.
5. A solid polymer fuel cell separator as set forth in claim 1 , wherein said low ion release conductive substance is one or more of VB, V 8 C 7 , and VN.
6. A solid polymer fuel cell separator as set forth in claim 5 , wherein said low ion release conductive substance has an average particle size of 0.01 to 20 μm and a mass ratio of metal oxides formed at the surface layer to the conductive substance particles as a whole is 30% or less.