Rocker panels on a vehicle are the sections of painted surface below the doors, along the bottom edge of the vehicle. The rocker panels are constantly exposed to water, salt, mud and other debris from the roadway that contribute to rust. Rust can eventually eat away the rocker panel and cause large holes. Repair your rocker panels before they have to be completely cut out and replaced. Repairs take skill and some special tools, but can be completed in less than one day.
Look at the damage on the rocker panel to see how much should be repaired. Draw a square around the damaged section that needs to be cut away. Use a square so you can replace the section cutting only straight lines, rather than circles or other shapes. Measure the square with a measuring tape.
Mark the exact measurements with a marker on the new section of metal that will replace the old rocker panel section. Cut out the square using sheet metal scissors. Hold the new square up against the rocker panel to make sure it is a good fit.
Cut the damaged section off of the rocker panel with an angle grinder, staying inside the marked lines. If you need to take off more, do it slowly and a little at a time. Hold the new metal square up to the square hole to make sure it will fit.
Grind the paint away from the surface of the vehicle, including off of the new square if it has more than a bare metal finish. Surface paint will weaken the welds. Grind until only bare metal is showing along the edges of the square cut into the rocker panel and on the new square.
Hold the new square in place on the rocker panel. If it is large, use vice clamps to hold it onto the vehicle. Use an MIG welder to attach the new square to the rocker panel by applying tack welds. Tack welds are made by touching the end of the welder to the metal and holding the trigger for one second then releasing it. Place tack welds all along the edges of the square, moving to opposite sides as you go, rather than making all of the tack welds along one side at a time. Sheet metal is very thin and if the welder is held up to it for longer periods, the metal can warp and shrink significantly. Allow the welds to cool for 30 minutes.
Grind the tops of the welds with a grinder and an 80-grit sandpaper disc until they are smooth. Cover the seam with body filler and allow the filler to dry for one hour. Smooth the filler by sanding it with 80-grit sandpaper (not with a grinder) until it is as smooth as the surrounding surface and the seam is no longer visible. Sand over it again using 220-grit sandpaper to smooth the scratches from the 80-grit paper.
Spray a coat of primer over the filler and allow it to dry for 30 minutes. Spray three to four coats of paint over the area, waiting five minutes between coats.
