We have hired people to clean our condo and use a type of corrosion products in our taps Kohler polished metal, and now it is discolored by black spots. Is there anything we can to remove stains?

Only sponge in a little white vinegar and sprinkle a little baking soda on your cloth or sponge and rub gently on leave for about five to ten minutes and then rinse with warm water and wipe dry. You can also use a little alcohol on a sponge and wipe with a dry cloth. Good luck!