Patent ID: 8304141

Claim:
A method of evaluation of warp and twist of 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 HL 1 , from the line CX is HL 2 , from the line OC is HC 1 , from the line LX is HC 2 , 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 > wherein said method of evaluation of warp and twist of a separator measures the 3D shape of said separator by a laser displacement meter and calculates digitalized 3D displacement data to calculate the values of equation <1> to equation <7>.