Corrosion of pure metals and alloys exposed in geothremal fluids derived from the Ohaaki-Broadlands geothermal resource in New Zealand are reported. Coupon materials of titanium (and two common alloys) a zirconium alloy a cobalt alloy tantalum and molybdenum were exposed for periods of upt to 1 year in two-phase fluid separated brine steam aerated steam condensate and aerated condensate. The kinetic surface corrosion results will be presented and then compared and contrasted with practical experience in power station applications.