How To Repair Surface Rust

Surface rust is a chemical reaction that happens when condensation comes in contact with bare metal. A surface treated with primer and paint will take longer to show surface rust depending on its environment; things such as harsh sunlight or corrosive material like road salt will speed up the rusting process. With a little time, patience and knowledge, you can save yourself a bundle and be proud of what you have accomplished.

Things You'll Need

  • Electric or air grinder
  • Air compressor
  • Bondo
  • Spray primer
  • Activator
  • Putty knife
  • Cardboard
  • Sanding block
  • Sand paper
  • Wet sand paper
  • Bucket and water
  • Grind the rust. Using either an electric grinder with a finish wheel, or an aircompressor and air grinder, begin grinding the rust in a gentle up and down motion. If you grind too long in one place or push too hard with the grinder, it will cause holes in the surface resulting in more damage.

  • Clean the surface and fill any imperfections. If the surface has any pits or scratches you will need to use Bondo to fill them. Start by cleaning the area with a solvent that will be strong enough to remove grease, then mix the Bondo. Scoop enough Bondo to do the job onto a piece of flat cardboard, then add the the amount of activator the directions suggest and start to mix thoroughly. When the Bondo is mixed, use your putty knife to spread it in an even coat over the surface, as this will fill any pits or imperfections.

  • Sand the Bondo. Using your sanding block and a rough 80 grit sand paper, begin to work the block in an X motion over the surface until smooth. Once this is done, use a finer 120 grit sandpaper to remove all the scratches from the 80 grit sandpaper. You are now ready to prime the area.

  • Prime the surface. Open your can of spray primer and shake it for 60 seconds; after this is done you may begin to spray. When spraying the primer, it's best to keep the nozzle 8 to 10 inches away from the surface to prevent runs. To begin spraying the primer, press down on the nozzle, sweeping the can one way, then the other in a slow smooth motion. After the primer is dry, sand the surface with a very fine, wet 1000 grit sandpaper.

  • Wet sand the entire area. Using a bucket of water and the 1000 grit wet sand paper, dip the paper in the water and begin sanding. When the paper begins to dry, re-wet it and continue sanding. When you can wet the surface with water, and it shines without any imperfections, you can re-coat it with primer. Once this is done, you are ready to paint the surface. Painting the surface will prevent surface rust from re-appearing for years, depending on its environment.