Iridium's extraordinary hardness, high melting point, and exceptional resistance to wear and corrosion make it the ideal material for spark plug electrodes in modern internal combustion engines. Iridium-tipped spark plugs can last up to 100,000 km — three to four times longer than standard copper or platinum plugs — while delivering more reliable ignition and improved fuel efficiency. The thin iridium electrode (typically just 0.4mm) requires less voltage to spark, reducing engine load and emissions. Iridium is also used in oxygen sensors, exhaust system components, and high-performance racing engines where reliability under extreme conditions is critical.

Iridium-based phosphorescent compounds are critical components in modern OLED (Organic Light-Emitting Diode) displays found in premium smartphones, televisions, and wearable devices. These iridium complexes enable vibrant colors, deep blacks, and energy-efficient operation. Iridium is also used in semiconductor manufacturing — particularly in the production of silicon wafers via the Czochralski process, where iridium crucibles can withstand the extreme temperatures required to grow ultra-pure single crystals. Additionally, iridium contacts are used in high-reliability electronic components for aerospace, defense, and medical electronics where failure is not an option.

Iridium catalysts play a key role in major industrial chemical processes. The Cativa process — which uses an iridium-based catalyst — is the modern method for producing acetic acid, a fundamental building block for synthetic fibers, plastics, pharmaceuticals, and food additives. Iridium oxide-coated electrodes are essential in chlor-alkali electrolysis for the production of chlorine and sodium hydroxide. Iridium catalysts also drive water electrolysis in proton exchange membrane (PEM) electrolyzers — a technology critical for green hydrogen production as part of the global energy transition. The exceptional stability of iridium under harsh chemical conditions makes it irreplaceable in these applications.

Iridium's combination of extreme heat resistance, density, and radiation tolerance makes it indispensable in specialized applications. In aerospace, iridium-rhenium alloys are used in rocket thrusters and satellite components that must operate at temperatures above 2,000°C. The international standard kilogram (until 2019) was a platinum-iridium alloy stored at the BIPM in Paris. In medicine, iridium-192 is a radioactive isotope used in brachytherapy to deliver targeted radiation treatment for cancer, particularly prostate, breast, and cervical cancers. Iridium is also used in industrial radiography for non-destructive testing of welds and structural components, in deep-sea ROV components, and as the gold standard for high-precision pen nib tips in luxury fountain pens.