PLATINUM IRIDIUM

Use

Iridium is the addition to platinum most oftenused to provide improved mechanical properties.It increases resistance to corrosion whilethe alloy retains its workability. Up to 20%iridium, the alloys are quite ductile. Withhigher iridium content fabrication becomesdifficult. Platinum–iridium alloys are employed forinstruments, magneto contacts, and jewelry.The alloys are hard, tough, and noncorrosive.An alloy of 95% platinum and 5% iridium,when hard-worked, has a Brinell hardness of170; an alloy with 30% iridium has a hardnessof 400. The 5 and 10% alloys are used forjewelry manufacture; the 25 and 30% alloys areemployed for making surgical instruments. An alloy of 80% platinum and 20% iridium is usedfor magneto contact points, and the 90–10 alloyis widely used for electric contacts in industrialcontrol devices. The addition of iridium doesnot alter the color of the platinum. The 5% alloydissolves readily in aqua regia; the 30% alloydissolves slowly.