Re: Must I need distilled water for my rusting of nails experiment?

Yes, you do need distilled water.

When iron rusts, basically what happens is that it oxidizes to form Fe2O3. 
 In order for this to happen, electrons have to leave the iron atoms so 
that it can get positive charge and bond with oxygen.  ("oxidize" comes 
from the element name "oxygen").  This process happens much more quickly 
when you have tap water, because there are other particles that have 
electrical charge floating around in it, such as calcium, magnesium, 
chlorine, and fluorine ions.  When these ions are present, it allows the 
electrons to leave the iron much more easily, and rust more easily.

By the way, the chlorine that is used to treat water is Cl2, or chlorine 
gas.  By the time the water reaches your faucet, this stuff has reacted to 
form chloride ions.  Although chloride ions are not corrosive, they do 
allow iron to rust more easily.

Hope this has helped!