Respuesta :

Corrosion. Metals tend to form oxide and over time, they rust. ( 2 FeO(OH) ⇌ Fe2O3 + H2O). Gold and platinum on the other hand are noble metals and remain stable in their pure form. Thus, no electron loss and no oxidation.
The metals lose their shine because they oxidize but gold does not oxidize so it does not lose shine.