There is no secret to protecting your car from corrosion. Your car's longevity can be increased dramatically by washing the bodywork on a regular basis - at least once a month. Use plenty of tepid water with a capful of proper car shampoo to break down greasy deposits. Domestic washing-up liquid should be avoided as it contains large quantities of salt.

Allow the body to soak before using a large, grit-free, soft sponge to remove the dirt.
Remove the wheels and ensure that any mud traps, such as the inner 'arches, are clean. Dry off any excess rinsing water from the outer panels with a quality natural chamois. An old chamois, or cheap synthetic cloth can be used to dry out the arches.
The underside of a vehicle, and its engine bay, should be steam cleaned once a year. Wax the paintwork with a good quality polish at least twice a year.

Your vehicle will be protected further from the ravages of rust when it is housed in a well-ventilated garage. If your budget will stretch to it, either a de-humidifier or Carcoon the blow-up bubble that draws moisture from your car - is excellent.
A cheap waterproof cover is not a good idea as it won't allow
water trapped below the material to escape. The more expensive covers are made from a Gortex-like material, which allows your vehicle to breathe.
You should polish your car once a month, including the chrome, which is slightly porous. Chrome is really thin and harsh abrasives will soon remove the shiny skin.

Do not use a high-pressure washer on the car's paintwork
at any time!!!!!