What prevents nails rusting?

A. If you have done any homework (research) on the subject you know that it takes iron, moisture and oxygen to get rust.
You could try light weight oil, heavier oils and modified materials like WD-40 [on eBay or Amazon] . You could also use varnish, shellac, paint, polyurethane, fingernail polish, butter or margarine (among many other things).
Some nails are plated. Some nails are glue coated. Some nails have a heavy black oxide coating. How are you planning to remove that so that each nail is exactly identical to each other one? Your experiment is a waste of time if you do not have this as a starting point.

A. Fazara,
Oil and vaseline will retard rusting but they will eventually wear off. There are many coatings used on nails today, but most coatings are not found at home or in a hardware store. You could lightly sand the nails with emery paper, clean well. Hang the nails with fine wire or fishing line, get a cardboard backdrop, and spray a few coats of clear lacquer over the entire surface of the nail(s). Make sure you have good ventilation and eye protection. Good Luck!

You're in 8th grade, you should be looking at how to anodize pieces of metal. There is a way to do it without buying expensive Chemicals. It's a really easy process to do. Just look up How to Anodize". There may be a topic here!

Nails are usually made of steel, John, and steel can't be anodized.