When exposed metal such as on your outdoor mailbox reacts with the oxygen in the air, a process called oxidation occurs. This is how rust forms on metal surfaces. Mailboxes are particularly vulnerable if left unprotected because they are usually full exposed to the elements, whether it is rain or snow. If your outdoor mailbox is rusting due to oxidation, it is easy enough to remove the rust. After doing so, you should take further steps to prevent rust from building up again by either painting it or coating it with a rustproof finish.
Step 1: Scrub the Mailbox
The first step is to remove as much of the rust as is possible with a wire brush or a piece of heavy steel wool. If your mailbox is removable, remove it and work on a shop bench or somewhere sturdy. The biggest rust flakes will scrub off in this manner, and in doing it, you will take off as much as half the rust.
Step 2: Remove the More Persistent Rust
You have your choice here. You can use either a commercial, chemical rust remover or a homemade solvent. If you use the chemical remover, make sure the cleaning area is very well ventilated. Wear both rubber gloves and a mask to protect yourself. Follow the application directions to know exactly how much rust remover to use and scrub the mailbox with the shop rag.
A non-toxic homemade solvent works just as well. White vinegar can be applied the same way as a chemical cleaner. With the shop rag, scrub the mailbox to get the persistent rust out. As an extra measure, spray lemon juice onto the rust areas, sprinkle it liberally with baking soda, and then apply the vinegar. It will react with the baking soda, foaming up and eating through some of the rust. Make no mistake, though, you should plan on scrubbing. It won’t come off by itself. Repeat Step 2 until the rust is removed.
Step 3: Rinse
Take a clean shop rag, wet it down and rinse the mailbox. Make sure you dry it thoroughly after you do so rust doesn’t have a chance to form anew.
Step 4: Protect the Mailbox
The last step is to protect your like-new mailbox from rusting in the future. Either coat it with a rustproof finish or pick a color and paint it. Both options will protect it from further rusting, although after time it will have to be repainted or refinished.
Removing the rust from your outdoor mailbox will take a couple of hours at the most. All that is required is a homemade (or chemical) solvent and a strong helping of elbow grease. Once you’ve removed the rust, protect it from rusting later on with a coat of paint or protective finish.