If you are into DIY (it's easier with a truck than a car, as you can get under without lifting it) look into the treatments people use for Land Rovers and other

If you are into DIY (it's easier with a truck than a car, as you can get under without lifting it) look into the treatments people use for Land Rovers and other 4x4s that they regularly drive off road. It's not just a one-off thing though, you should reapply it every few years - this is why cars still rust that have the undercoating the dealer upsells you.