Background

Gold and palladium are totally soluble in one another. The primary use of gold / palladium alloys is in jewellery. The alloy is more commonly known as white gold and is an alternative to platinum. Gold / nickel alloys are also used as white gold. In both cases some other metals may be present in small amounts such as silver, zinc and copper. The cost of palladium white golds are greater then that for nickel white golds due to palladium higher cost and more difficult processing. Palladium white golds are also softer and more ductile compared to nickel white golds. In both cases it is not possible to have white gold with a purity greater than 21 carat. The composition of some palladium containing white golds are as follows: Gold Palladium Silver Copper Zinc Nickel 18ct 75 20 5 75 15 10 75 10 15 75 10 10.5 3.5 0.1 0.9 75 6.4 9.9 5.1 3.5 1.1 75 15 3.0 7.0 14ct 58.3 20 6 3 1 58.5 5 32.5 20.5 1.4 10ct 37.5 52 4.9 4.2 1.4

Key Properties

The addition of palladium to gold: · Increases its melting point · Increases its modulus of elasticity · Increases its strength · Increases its hardness · Turns yellow gold white (depending on the amount added)

Applications

The primary use of gold / palladium alloys in for jewellery, also known as white gold. However, gold / palladium alloys are also used in dentistry and they were used as spark plug electrodes, but the alloy has now been replaced by platinum.