Simple dish soap should do the trick. After the surface is clean, start with pure lemon juice — not a diluted version, as the stronger the acid the better it will remove the stain. Once you've soaked the stain thoroughly with the lemon juice, let it sit. This is key.
Does vinegar remove rust from concrete?
White vinegar and a little scrubbing with a brush is a very effective, eco-friendly way to remove rust stains from concrete—even those that are decades old. Pour the white vinegar directly onto the stain, allow the liquid to penetrate the area for 20 minutes, and scrub with a stiff-bristled brush.
What is the best rust remover for concrete?
If you need to get rid of rust from concrete, your best bet is to use some WD-40 Multi-Use Product, and some elbow grease. WD-40 is specially formulated to be a penetrant, so when you spray it on a rusted surface, it gets to work right away by getting under the rust.