Many homeowners may face the issue of unsightly rust stains on their concrete surfaces. It’s a particularly common problem for those who use well water, since well water can contain high levels of iron. Often, the rust appears so gradually that once you finally notice that your nice grey driveway has a red tinge to it, the stain has already been months or years in the making, and can be difficult to remove as a result.
But fear not – we’ve put together a handy list of methods you can use to remove rust stains from concrete, from gentle treatments that are helpful with minor stains, to more heavy duty solutions for extra tough spots.
Before beginning any rust removal treatment, wash and rinse the affected concrete with soap and water to remove any dirt or dust that can make the rust more difficult to remove. Ensure you allow the concrete to dry before proceeding.
If the stain is relatively small and fresh, you may wish to start out with a natural treatment method, before progressing to commercial grade products if needed.
The vast majority of rust removal products use acid to lift the stain, so if you’re looking for a gentle, more natural alternative, lemon juice can work wonders thanks to its high concentration of citric acid. Pour or spray lemon juice onto the stain and let it sit for 10 minutes, then scrub away the stain using a wire brush before rinsing with cold water. If you’re removing rust from smooth or painted concrete, it might pay to use a stiff bristled nylon brush instead of wire.
You can repeat the process if needed, once the concrete has dried – many stains take multiple washes before the rust completely disappears.
If you’re wanting to avoid commercial rust removers but the lemon juice just isn’t doing the trick, try white vinegar for removing slightly tougher stains. Again, pour or spray it onto the site of the rust and let it sit for several minutes before scrubbing, rinsing with cold water, and repeating as necessary. For best results, try scrubbing in small circles.
For delicate or painted surfaces, dilute the vinegar and then use a sponge with warm water to scrub, to avoid damaging the finish. It’s also a good idea to test the vinegar on a small corner section first, to make sure it doesn’t strip the paint.
For larger or more persistent stains, you’ll likely need to invest in a more heavy-duty solution, and look into some commercial cleaners. These will come with their own specific safety precautions and instructions for use, so make sure to read the label and follow the directions carefully. As a general rule, these products should be used in a well-ventilated area, and you should wear gloves and eye protection as well as long sleeved shirts and pants to protect your skin.
Cleaners that contain oxalic acid are frequently used to lift tough rust stains. They typically come in either liquid or powder form. Spray or sprinkle the product onto the affected surface, and in the case of powdered cleaners, add some water as per the directions on the product. Allow it to sit for several minutes, then scrub in small circles with a stiff bristled nylon brush to lift the stain, before rinsing thoroughly with cold water. Take care to remove all of the product, as leaving it on for too long can cause discolouration.
Trisodium Phosphate (TSP)
Another commercial cleaning product that’s ideal for removing stubborn rust stains from concrete is trisodium phosphate, or TSP, which can be purchased from a home improvement store such as Bunnings, and then needs to be mixed at home prior to use. Wearing protective gloves, mix half a cup of TSP with half a gallon of hot water, then pour the mixture onto the rusted surface and allow it to sit for up to 20 minutes. Scrub in circles with a stiff nylon brush as before, making sure that all of the product is rinsed off afterward.
Hydrochloric acid is a heavy duty treatment method for particularly tough rust stains, and is extremely effective, but must be used with great caution. It should always be mixed with water to prevent an adverse chemical reaction – we suggest one cup of water for every two cups of acid. Apply the diluted acid to the stain and let it soak for up to ten minutes, before quickly scrubbing the rust away and then rinsing the surface thoroughly with water. If left on for too long, the acid can cause concrete to turn blue, so make sure you’re ready to act quickly upon application. You can repeat as necessary until the stain has disappeared.
Also known as water blasting, a pressure washer is a super helpful tool for removing stains that are especially tough or difficult to reach. You can use a pressure washer to rinse away your cleaning product while putting concentrated force on the stain to lift it off the concrete surface.