Corrosion resistance of W and Ta based amorphous coatings in a geothermal steam environment – A combinatorial study

•WSi and TaSi are amorphous in a large composition range when prepared by sputtering.•TaSi amorphous coatings are highly corrosion resistant in geothermal steam.•WSi amorphous coatings undergo severe corrosion in geothermal steam.•Combinatorial methods are extremely efficient in screening for corrosion resistance. Amorphous films of WSi and TaSi have been deposited by DC magnetron sputtering in order to determine their corrosion resistance in geothermal steam. A combinatorial approach is employed whereby samples with composition gradients are deposited and analysed for amorphicity, temperature stability and corrosion resistance. WSi and TaSi form amorphous metal alloys over the composition range 4–60 at.% W and 12–80 at.% Ta, respectively. The amorphous structure of both alloys is stable up to temperatures well exceeding those encountered in a geothermal power generation environment. W-based amorphous alloys undergo severe corrosion when subjected to 30 days in geothermal steam whereas Ta-based amorphous alloys are not significantly affected by the same conditions. This shows that combinatorial methods can be employed to screen efficiently corrosion resistant materials and that Ta-based amorphous alloys are promising for applications in geothermal power generation.