Iridium is chemically stable. It is the most corrosion-resistant metal. Iridium has extremely high chemical stability to acid and is insoluble in acid. Only spongy iridium will slowly dissolve in hot aqua regia. If it is dense iridium, even in boiling aqua regia, Also can not corrode; But, in the high-temperature pressurized airtight reaction kettle, iridium is obviously corroded in the aqua regia above 250 ℃; The mixed acid configured by 20 parts of concentrated hydrochloric acid and 1 part of concentrated nitric acid, under the same temperature and pressure, The corrosiveness to iridium is about 20 times that of aqua regia, so it is often used as a reagent to digest metallic iridium in chemical analysis.

Oxides and Oxyacids
Iridium dioxide (IrO2) is a brown powder and is the only oxide of iridium whose properties have been well studied. Iridium trioxide is a black-blue powder that oxidizes to IrO2 in nitric acid. Other known compounds include iridium disulfide, iridium diselenide, diiridium trisulfide, and diiridium triselenide, etc. In addition, studies have pointed out the existence of IrS3.
halide
Iridium does not form monohalides and dihalides, but forms the corresponding trihalide IrX3 with each halogen. The only halides with oxidation state +4 or above are iridium tetrafluoride, iridium pentafluoride and iridium hexafluoride. Iridium hexafluoride (IrF6) is a highly reactive volatile yellow solid with an octahedral molecular structure. It decomposes in water, and iridium black (i.e. metallic iridium powder) reduces it to crystalline iridium tetrafluoride (IrF4).