Where would an anon go to auto-didactically learn the subject of chemistry? Assume I have almost zero knowledge on the subject(I really don't). I'm extremely interested in how chemicals actually interact or are made.

Like where would one start to figure out the reason WHY boiling a rusty piece of steel in water causes it to turn black? I know from online reading that H20 will give up it's oxygen molecule to the iron oxide to form FE O2 or O3(can't remember which) which will form magnetite, which is a traditional gun finish known as bluing.

My question is why does it do that? Are there any good resources online to learn this sort of stuff?

Pic unrelated.