About conducting solution...

conducting solution can be:

(1) a solution contains ionic compounds, such as sodium chloride
(2) an acid, such as HCl, H2SO4, and HNO3

reasons: These solutions contain mobile ions that increase the electrical conductivity, hence speed up the rusting process.

other reasons that can speed up the rusting:
(1)high temperature, speed up the reaction rate
(2)large surface area exposed to water/air
(3)attached to a less reactive metals, such as lead, copper, mercury