Rust is a persistent stain that quickly spreads to other areas. Rust is most often transported by dripping water or by an object being in direct contact with rusty metal. It is common for homes with aluminum siding to develop an occasional rust stain. They are typically easy to deal with as long as you catch them early and do not give the rust an opportunity to set in.
Things You'll Need
Bucket of soapy water
Water hose with power nozzle
Bottle of CLR
Mr. Clean Magic Eraser
Rinse the stained area of the aluminum siding with a water hose. Use a high-pressure spray nozzle to spray the area thoroughly. You may wash away a portion of the rust just from the initial rinsing.
Use a stiff brush and a bucket of soapy water to clean the stained area of the aluminum siding. Rub the siding hard and wash away as much rust as possible. Aluminum siding is durable and you don't have to worry about scrubbing too hard. Use the water hose to rinse the area after you have finished cleaning the siding.
Scrub the wall with a Mr. Clean Magic Eraser. The Magic Eraser is an all-purpose cleaner that works great on anything except for highly polished surfaces. Get the Magic Eraser wet and use it to scrub the aluminum siding. Rinse the siding after using the Magic Eraser. In most cases the rust stain will be gone by this point. If not, continue to the next step.
Use CLR to remove any remaining rust from the aluminum siding. CLR stands for Calcium, Lime and Rust Remover. It can be purchased at any hardware store. Rub CLR directly onto the area using a sponge or the remnants of the Magic Eraser, then rinse with a hose. Be advised that CLR may dull or even remove paint on your aluminum siding, so it is recommended to only be used as a last resort.
Many people use WD40 to remove rust, as it will begin to break apart and dissolve rust on contact.