A: Oxalic acid is a potent but toxic cleaner that removes rust and stains caused by iron, water and tannic acid. It's available in dry crystal form, to be dissolved in warm water for use.

Q. I have a nice-looking terrazzo floor that has rust spots made by paint cans left on it. I tried removing the rust with Rust Reformer and a little bleach rubbed with steel wool, but nothing worke… ...

Rust stains can sometimes be removed from concrete by scrubbing with a solution of four ounces of oxalic acid in a quart of water. Oxalic acid is sold in crystal or powder form at paint stores.

Oxalic acid solutions are the go-to cleaner for exterior redwood. If you recall your high school chemistry, you know that acidic solutions have a pH lower than 7.

After this victory, I went to the garage to see if the oxalic acid would remove harsh rust stains left on the concrete floor from the bottom of my snowblower.

Make a solution of oxalic acid crystals (available in paint stores) to saturation in hot water in a plastic bucket; never use metal with oxalic acid. Apply it to the stains with a paintbrush.

Potatoes This might sound like a weird thing to use to remove rust stains, but it works because potatoes are high in oxalic acid.

A small amount of ferric oxide is added to a solution of oxalic acid, a commonly used cleaning and bleaching agent. Once the rust is dissolved, potassium carbonate is slowly added to the solution ...

Potatoes contain oxalic acid, a natural compound that helps dissolve rust by breaking down iron deposits. When paired with salt as an abrasive, a cut potato can effectively scrub away rust from ...

This is because the rust can soak into these surfaces. You just have to be very patient and try to work in the shade so the oxalic acid solution doesn’t evaporate.