The v rails used are uncoated steel and can corrode over time. I did not treat my rails for over a year. The only place I saw any real corrosion starting was near an area where I accidentally cut some vinyl and the evil brown gas got to the rails.
The rails ship with a light coating of oil to prevent corrosion. I think this helps a lot, but when rails are glued on, this oil needs to be removed. I have re-oiled them with Starrett M1. This is basically designed for what we need. It dries "to leave a dry-lubricating, surface protecting film". I am sure other materials will work too, but you probably should apply something.