Rust,corrosion experiment,please help?!?!?!?!?!?!?!?

I need help.im in 9th grade and i need to do a research project that has to be pretty advanced.right now im going to do an experiment where im take nails comparing them to see which one rust fast like,one will be a regualr steel one,one will be painted,one will be galvanized and there will two nails used together as cathode protection.how can i make it better?i need answeres asap,please!!!!!!!!!!!!!!!!!!!!!!!!