Q. I have tried removing rust stains on these stone columns (on testing the base is limestone), and I believe the columns are the same? I've used a number of different branded products and oxalic acid but none of these have removed/lessened the stain, any advice on product, maybe a poultice for longer dwell, I just don't want to cause secondary damage in the stain removal.
A. It's clear that you’ve approached this thoughtfully. On limestone, rust stains can be particularly stubborn, and it’s common for early attempts to fall short when the iron has penetrated more deeply into the stone.
Oxalic acid and off-the-shelf rust removers are often effective only on relatively fresh or shallow staining. If the staining has been present for some time, the iron can migrate into the pore structure of the limestone, at which point surface applications will have little visible effect.
For older, more deeply set stains, a poultice is usually required. A poultice draws the stain out of the stone over time. For detailed, step-by-step instructions on how to mix and apply a poultice correctly, check out our free Stain Management App. Your poultice ingredients will be a rust remover and diatomaceous earth or a proper poultice powder. Do not to use clay-based powders. You can expect the stain to lift gradually, with multiple poultice applications.
If a standard rust-remover poultice does not produce the desired results, the safest next step would be to consult a professional stone restoration contractor experienced with limestone and rust staining. To find a vetted PRO in your area, visit www.surfacecarepros.com and click on Find a PRO.
Your PRO may choose to poultice with hydrofluoric acid. This chemical is extremely hazardous and can permanently damage stone if misused, so it would be best to leave this to a PRO.They can assess the depth of the stain, carry out controlled testing, and balance effective removal with the least possible impact on the stone’s surface and finish.
NOTE: Bleach should never be used on rust staining, as it can actually intensify the discoloration rather than remove it.
Rust is one of the most difficult stains to remove, even for a PRO. Set your expectations accordingly.
ABOUT THE AUTHOR Fred Hueston is the Chief Technical Director at SurfaceCarePROS.com and Director at StoneForensics.com. He is also the author of Stone and Tile Restoration: The Manual, a comprehensive online manual for stone and tile restoration contractors. [Learn more about Fred.]
Article ID: 855
Created: January 11, 2026
Last Updated: January 11, 2026
Author: Fred Hueston
Online URL: https://surfacecarepros.com/kb/article/how-to-remove-rust-stains-on-limestone-without-causing-damage-855.html