Things You'll Need
Rust can ruin the appearance of tile grout in the shower by discoloring and adding a dirty, metallic texture to the otherwise smooth and uniform surface. Worst of all, if you try scrubbing rusty grout with a conventional bathroom cleaner and sponge, you are likely to find yourself laboring in vain. To take control of the situation, you must apply a more appropriate acidic solution.
Fill a spray bottle with white vinegar, full strength. Though highly resistant to many household cleaning products, rust is vulnerable to acids like the acetic acid found in vinegar. As an alternative, fill the spray bottle with lemon juice and add a few sprinkles of salt. The combination of sodium chloride and citric acid can also remove rust.
Spray your cleaning solution along the grout lines anywhere that you find rust. If dealing with a tile wall, hold the vinegar in place by squirting it onto paper towels and pressing them against the rusty surface. Allow the acid to penetrate the rust for about 10 to 15 minutes before proceeding.
Remove the paper towels, if needed, and apply a second coating of the cleaning solution to the rust. Add new paper towels if necessary, and continue to check back periodically. If at any point the grout feels dry, apply more solution. Grout is highly porous and will absorb the liquid.
Scrub the grout with a cloth or sponge, after soaking the stains for about an hour. If the rust breaks away from the grout, rinse the surface with water. If the rust still refuses to break away, apply more cleaning solution once per hour. It may take several hours for the acid to weaken the rust.
If you choose to use vinegar to clean your rust, do not add salt, as the mixture will create hydrochloric acid, which may be too strong for some grout surfaces.