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Remove Rust From The Backside Of An Air Conditioner And Clean The Unit's Exterior

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If moisture has caused the backside of your window air conditioning unit to rust, treat the corroded areas with the following steps. Afterwards, clean the portion of the unit that is outdoors and apply an even coat of spray that is designed to prevent rust on the unit's exterior.


  • step ladder
  • hand broom
  • rust disintegrating gel
  • paintbrush
  • sponge with rough surface
  • water
  • metal cleaning agent
  • soft cloths
  • plastic sheeting
  • rust preventive spray

Remove Loose Dirt And Rust

Turn off the air conditioner and go outdoors. While standing on a stepladder, wipe the top of the unit off with a hand broom. Apply a thick coat of rust disintegrating gel to each rust spot with a standard paintbrush. Once the rust spots begin to loosen, move a sponge with a rough surface over each one to remove them.

If rust spots do not respond well to the first treatment, add a second application of disintegrating gel to each one. Use a clean sponge that has been dipped into water to remove loose flecks of rust and any gel that remains on the air conditioner's exterior. 

Clean The Unit's Exterior And Apply A Protective Layer

Remove dirty buildup from the unit's exterior with a soft cloth that has a few drops of a metal cleaning agent applied to it. Remove the cleaning agent with water and a clean cloth. Dry the unit's exterior off with a towel. In order to prevent rust from forming on the portion of the unit that was previously affected, apply a rust preventive spray to the metal. Before applying the product, cover the ground that is directly underneath the unit with plastic sheeting.

The sheeting will catch any drips and prevent grass or plants from being exposed to chemicals that are contained in the preventive spray. Apply an even coat of the rust blocking product to the air conditioner's metal exterior. Wait for the product to dry thoroughly and add a second coat of the product to ensure that each metal part has been sufficiently covered. After the second coat of spray has dried, the air conditioning unit will be protected from damage associated with moisture.

Remove the sheeting from the ground and use the air conditioner in a normal manner. In order to prevent dirty buildup from becoming an issue, remove loose debris from the part of the unit that is located outdoors on a regular basis.