Adding salts, oxidizers and acids to the water speeds up the process, causing rust to appear faster on the surface of the metal, according to the Seattle Post-Intelligencer. Rust occurs in the presence of iron, water and oxygen in a chemical process called oxidation.
Combining ordinary salt with water and metal improves the capability of water to carry electrons and increasing the rate of oxidation. Adding bleach to the water causes the iron to lose electrons faster than plain water, which also speeds up causing visible rust to appear. Vinegar is an acid, which accelerates removing electrons from the metal and produces iron acetate on the metal surface.