(source: https://www.rsc.org/periodic-table/element/77/iridium)

Iridium is the most corrosion-resistant material known. It is used in special alloys and forms an alloy with osmium, which is used for pen tips and compass bearings: Osmium Alloy (1926). 

It is also used for the contacts in spark plugs because of its high melting point and low reactivity:

Supported iridium alloys can be used in catalysis: Hydroforming With Promoted Iridium Catalyst (1971).


All patent information has been obtained from Espacenet (European Patent Office).