Titanium material for fuel cell separator having low contact resistance

A separator for a fuel cell comprising a titanium material, the titanium material comprising:

• a titanium alloy substrate comprising at least one noble metal element selected from the group consisting of platinum group elements, Au and Ag;
• and
• a layer of a mixture formed on a surface of the titanium alloy substrate, the mixture comprising a noble metal element precipitated from the titanium alloy substrate and a titanium oxide formed from the titanium alloy substrate, and said layer having an average thickness of up to 200 nm;
• wherein:
• the mixture layer on the surface and the titanium alloy substrate have a conductivity in terms of contact resistance of up to 10 mΩ·cm2;
• and
• contact resistance is determined by:
• placing a carbon cloth having an average thickness of 0.3 mm on opposite surfaces of a sample of the titanium alloy substrate having the mixture layer formed thereon:
• sandwiching the sample of the titanium alloy material with a pair of copper electrodes via the carbon cloth, the copper electrodes each having a contact area with the titanium alloy material of 1 cm2;
• and
• measuring a voltage drop between the carbon cloths by using a four terminal ohmmeter while pressing the copper electrodes against the sample of the titanium alloy material at a surface pressure of 5 kg/cm2 by using a hydraulic press and applying an electric current of 7.4 mA between the copper electrodes.