Stainless steel contains chromium, and other alloying elements that keep them bright and rust resistant in spite of moisture or the action of corrosive acids and gases. Because of their shining surfaces, architects often use them for decorative purposes. Stainless steels are used for the pipes and tanks of petroleum refineries and chemical plants, for jet planes, and for space capsules. Surgical instruments and equipment are made from these steels, and they are also used to patch or replace broken bones because the steels can withstand the action of body fluids. In kitchens and in plants where food is prepared, handling equipment is often made of stainless steel because it does not taint the food and can be easily cleaned.