Titanium material for fuel cell separator having low contact resistance

Abstract

A separator for a fuel cell comprising a titanium alloy substrate containing at least one noble metal element selected from platinum group elements, Au and Ag; and a layer of a mixture formed on the titanium alloy substrate, said mixture comprising the noble metal element precipitated from the titanium alloy substrate and titanium oxide, 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 as determined by the following method of up to 12 mΩ·cm. The contact resistance is determined by placing a carbon cloth having an average thickness of 0.3 mm on opposite surfaces of the titanium alloy substrate having the mixture layer formed thereon; sandwiching 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 cm; measuring voltage drop between the carbon cloths by using a four terminal ohmmeter while pressing the copper electrodes against the titanium alloy material at a surface pressure of 5 kg/cmby using a hydraulic press and applying an electric current of 7.4 mA between the copper electrodes; and calculating the contact resistance from the measured value.