Lawn mower decks eventually wear out and rust through from grass and debris sticking underneath them and keeping the metal wet. Clumps of grass and leaves on the bottom of a mower are a fire hazard. A graphite undercoating is the best way to protect a lawn mower deck and it is easy to apply to extend the deck's life almost indefinitely. Graphite forms a hard, slippery coating to inhibit corrosion and rust on metal surfaces.
Remove the riding lawn mower's deck according to the instructions in the owner's manual. Each make and model is different. Place the lawn mower deck upside down on a flat, level surface.
Tilt a push lawn mower or self-propelled model on its side with the gas side tank pointing upward. Place bricks in front and behind each wheel to properly brace it and prevent it from tipping over on you as you work. Make sure the mower is turned off and remove the spark plug boot on a gas model. Unplug an electric mower.
Clean and Smooth
Wash the deck's underside thoroughly with a strong stream of water from a garden hose. Scrape any stuck-on grass or debris from the deck with a plastic scraper. Put on safety glasses and use a wire brush to remove rust particles or any loose particles under the deck and allow it to dry completely.
Applying the Graphite
If you are applying an aerosol graphite, shake the can vigorously for several minutes to mix the contents. Remove the cap, press the spray nozzle and coat the entire underside of the deck and the blades in even, long, overlapping strokes. Don't forget to put newspaper or another material underneath so the surface underneath doesn't get painted.
Shake a can of paint-on graphite undercoating, remove the lid with a screwdriver and stir it with a paint stick. Dip a paintbrush into the coating and paint it on the deck and blades in a thin coating to cover all the metal areas.
Allow the coating to dry for 24 hours and apply a second coat on it in the same manner. Allow it do dry for another 24 hours before using the lawn mower.
After each use of the lawn mower, spray the underside of the deck with a garden hose to remove all grass clippings and debris. This should not take long because the coating means that dirt and grass slide off easily.