As with toilets, standing water can mar the shine of chrome. The result isn't a stain, but mineral build up. As water pools around faucets and drains, the minerals settle to the bottom and eventually landscape the sink or tub with a rocky little ridge of calcium carbonate, also known as limescale or simply lime.
Commercial cleansers that are formulated specifically to dissolve lime and other mineral deposits have a drawback, besides toxicity concerns. They can discolor and damage chrome and stainless steel, as well as brass, bronze and nickel finishes. Vinegar, on the other hand, dissolves lime without harming metal. It works more slowly, however, and must be applied continuously. To keep vinegar from drying up or running off before it can do its work, mix it with baking soda to form a paste. Thoroughly coat the lime. Let it sit for a few hours, then rinse off [source: Sian]. Heavy deposits may take several applications to get rid of.
Next, baking soda takes on a hidden aspect of the world of bathroom cleaning.