How to safely clean Indiana limestone house siding?

My LP gas pipe apparently has rusted and left a long ugly line of rust on the exterior of my home. Our siding is made of Indiana Limestone held in place with a cement type grout product that is tuck-pointed. I need a solution to cleaning this soft limestone that will remove rust and not harm the stone of the grout.I know not to use a pressure washer in this situation but am looking for a product – purchased or homemade to remove the rust. I thought I’d try soft scrub first?
Other suggestions?
  7 answers
  • Grandmaquilts Grandmaquilts on May 28, 2015
    Saving foam! I saw this on HGTV a few years ago. They clean up a smoked-stone fireplace by spraying heavily with Shav foam and letting it dry...then brushed it off. Done. Sounds gentle. Hopefully it will work for you. Alternately, my mom used to remove rust stains on clothing using a paste of lemon juice and salt..soaked in the sun. Good luck!
  • Tambra Tambra on May 29, 2015
    I've used Iron Out in my washer for years when we had a well & it never harmed the fabric. Rust stains are a different animal altogether. Another option is to call someone in your area who sells architectural stone & ask them.
  • Maria Maria on May 29, 2015
    Product called "rust aid", in the plumbing dept at Home Depot
  • White Oak Studio Designs White Oak Studio Designs on May 29, 2015
    Just looked at what is in CLR: acid an solvents....not sure that is right for limestone...any other input? Calcium Lime Rust, more commonly known as CLR, is a household cleaning product used for dissolving stains, such as calcium, lime, and iron oxide deposits. Its ingredients include water, lactic acid, gluconic acid, lauramine oxide, Propylene Glycol, n-Butyl Ether, and solvents that dissolve cobalt gel coats and paint.
  • Duv310660 Duv310660 on May 29, 2015
    You might try Bartender's Friend... it has a cleaning acid too, but I find it very gentle (oxalic acid, like rhubarb.)
  • Lorraine McKay Lorraine McKay on May 29, 2015
    When we lived on a boat, we used lemon juice, salt and sunshine to clean up rust stains on everything (even fabric). The lemon juice is an acid and, if your limestone is polished, will slightly etch the surface. However, I think that would be lots less noticeable than a rusty mark.
  • Jean DeSavage Jean DeSavage on May 31, 2015
    You might try white vinegar-it's an acid also, and we know it's gentle. I would think it would not hurt the limestone.