The product is truly miraculous. The floor (with tiles) of the boiler room had rust everywhere for over 15 years and it cleaned in 10 minutes. The same applies to rusty metal objects that I cleaned. However, even though it says it is for stone and marble, it was tested carefully on small rust stains on gray stone and left white marks that do not go away, meaning the stone was corroded. I did it with cotton swabs in 1 or 2 spots and luckily, because if I had used a brush, it would have been a disaster. Try it somewhere that is not visible, let it work and then decide if you want to risk it.

Miraculous. I have used it again and again on various rusty irons and it impresses me every time. Suitable for removing rust from marble or other hard surfaces (granite, tiles). I apply it with a brush and let it act according to the instructions for use. For stubborn rust, I do it more than once. It smells and you need to take precautions to avoid contact with your body.