In a alloy which is primarily responsible for corrosion resistance
Gold is primarily responsible for producing corrosion resistance, but it also is relatively soft and requires other alloying element additions to solution-harden the composition. Copper is the primary alloying element that increases the hardness of the material. However, copper also tends to make the color less yellow and more orange. Silver is added to offset the color contributions of copper. Palladium is added to increase the hardness of the alloy and has a strong whitening effect. Both palla- dium and platinum tend to raise the melting range for the alloy. Finally, zinc is added as a processing aid to scavenge oxygen at the surface of a melt and prevent oxidation and loss of other key elements during the casting procedure.
Gold
Silver
Mercury
Zinc