Rusting

If an iron nail were submerged in vinegar, the acetic acid in the vinegar would slowly dissolve the iron and produce hydrogen gas. However, vinegar is a dilute solution of acetic acid, and the reaction would likely be quite slow.
If you soak an iron nail in vinager in the first day,we can see that the nail, it becomes brown coloured. this is because of the reaction taken place between a metal and an acid the vinegar will become yellowish. The acetic acid in the vinegar would slowly dissolve the iron and produce hydrogen gas after 3 days. If it is a new nail it will probably just turn dark. If it's a rusty nail it will become rust free.

It doesnt take so long, i think half a day you can see the result