What can corrode?

Yes Brass can corrode especially if coupled to a more noble metal in which case it will undergo Galvanic Corrosion. Amines and Nitrogen containing compounds can cause Stress Corrosion Cracking.

things corrode because of oxidation, which is when oxygen takes away electrons from a metal.This usually happens when a metal is soaked in water or copper chloride.

Unfortunately yes. Iron , especially when wet and even more especially when in salt water, oxidises to form rust. This means that all iron and steel products (eg nails, bicycles, cars) and buildings...

All acids contain hydrogen plus ions and these ions react with almost everything because hydrogen only has 1 valence electron to use. The reaction causes iron or any thing else to weaken.

Oxygen corrodes iron.