Things You'll Need
10 percent phosphoric acid solution
Phosphoric acid is a strong chemical that can remove tough stains from the surface of stainless steel. This substance is particularly useful in removing rust stains caused by carbon steel contamination, according to the British Stainless Steel Association. You can purchase phosphoric acid dilutions or phosphoric acid-based cleaners at a hardware or home improvement store.
Put on gloves. Phosphoric acid could irritate your skin.
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Apply phosphoric acid to a sponge.
Rub the sponge over the stainless steel until it is completely soaked.
Brush the acid-covered surface of the stainless steel. Do not use a coarse brush or a brush with metal bristles, as this will scratch the metal's surface.
Dip another clean sponge in ammonia and rub it over the stainless steel surface to rinse away the phosphoric acid. The ammonia will neutralize the acid to ensure that it doesn't eat through the stainless steel.
Dip a third sponge in clear water and rinse away the ammonia.
Dry the stainless steel with a clean cloth to prevent watermarks or streaks from drying on it.