up here in the great white north.
we have a company called CROWN RUST CONTROL
for $135.00 they spray every nook and cranny they can get to,, they even drill holes in the cab and fenders
to spray every nook and cranny in there too.
but i found out the hard way they do not warranty the frame or suspension components
just the body parts.
soooo i now use CASTROL MOTORCYCLE CHAIN LUBE .this stuff is great the emolients in the aerosol kill the active surface rust bacteria on contact ,, and it sticks to rust like glue,, the deeper rust bacteria die of oxygen starvation when the chain lube semi dries
and it keeps moisture in the metal ,, so you do not get that annoying squeaking after every bump you drive over.