How to deal with Rust/Corrosion on Case?

[daym4n]

I'm fairly new to this wonderful hobby and eager to learn more. Recently, I stumbled upon a vintage Omega timepiece in 18ct yellow gold. However, upon closer inspection, I noticed some rust/corrosion on certain parts of the case.

Before I decide on whether to purchase it or not, I would greatly appreciate your advice on how to properly care for such cases. Is it advisable to seek professional assistance for cleaning and rust removal? Alternatively, since the rust/corrosion is not noticeable without magnification, would it be best to leave it untouched?

Additionally, I'm curious to know if rust/corrosion is common in solid gold watches or if this is an unusual occurrence.

Below are pictures of said rust:






Thanks for your help!

 

[JimInOz]

It's not rust, you only get rust on ferrous (iron) based metals.
The colouration is simply tarnish that occurs on gold that is less than 100 percent pure. For example, 18 carat gold contains other metallic elements (silver, copper etc) and these lead to the tarnish effect.
It's not serious and can easily be removed safely with a jewellery polishing cloth, but many owners like the effect as it gives gold vintage watches a nice aged patina.

 

[Davidt]

What Jim said.

A cape Cod/Town talk cloth would remove that but in person it has a real warmth and charm so I’d consider keeping it.

 

[MtV]

This discoloration can even get pretty colorful: