Do Gold Coins or Bullion Rust?

By GovMint :

Gold coins and bullion do not rust because gold is a noble metal, which means pure gold is impervious to corrosion and will not react to oxygen or moisture. Pure gold, such as 24-karat gold, remains unaffected by rust or tarnish. However, gold alloys, which are mixtures of gold with other precious metals like copper, can sometimes develop tarnish or discoloration due to the presence of these other metals. Lower-karat gold, which contains a higher percentage of base metals, will be particularly susceptible to tarnishing. 

Sources Used:

https://kdmfab.com/melting-point-of-gold/