If salt and sand on roadways have caused rust to form on the underside of your vehicle, clean and treat the corroded spots by completing the steps below. Once finished, apply a coat of automotive primer and a couple coats of an undercoating product to the underside of your car to prevent damage from occurring again.


  • car lift
  • degreasing agent
  • sponge
  • water hose
  • power grinder
  • metal sandpaper
  • painter's tape
  • automotive primer
  • mixing stick
  • paint trays
  • wide paintbrush
  • automotive undercoating

Apply A Degreaser And Treat Rust Spots

Use a car lift to hoist your vehicle so that you can clearly see the corroded areas. Dampen a sponge with water before pouring a degreasing agent onto the sponge. Move the sponge firmly back and forth over dirty portions of the undercarriage. Use a water hose to spray the base of the vehicle with a strong stream of water and wait for the treated areas to dry.

Use a power grinder to eliminate thick patches of rust. Move the grinder back and forth as you apply pressure to the backside of the tool. If rust spots are located in small crevices, move a piece of metal sandpaper back and forth over each one. Spray water against the bottom of the car to eliminate sanding residue and wait for the surface of the undercarriage to dry.

Apply Automotive Primer And An Undercoating Product

Secure strips of painter's tape over parts of the car that are near the undercarriage so that primer and the undercoating product will not accidentally be applied to them. Open a can of automotive primer. Use a mixing stick to stir the primer for a minute or two. Pour the primer into a paint tray. Use a wide paintbrush to apply an even coat of primer across the underside of the vehicle. Allow plenty of time for the automotive primer to dry.

Open a can of an undercoating product, like ValuGard, and stir the can's contents. Pour the undercoating product into a clean paint tray. Use a wide paintbrush to apply a coat of the undercoating product over the primed surface. Once the undercoating has dried, add a second coat of the product to ensure that the entire undercarriage has been covered sufficiently. After the second coat has dried, carefully remove the strips of painter's tape before lowering the car lift. You can now drive over roadways without needing to worry about your car being susceptible to damage.