It comes as a surprise to many that the primary alloy contained within stainless steel is humble and familiar iron. But there's a reason, after all, that this manufactured metal is called stainless steel. To this mundane and plentiful iron ore other, more exotic, alloys-such as chromium and nickel-are added, giving stainless steel its corrosion-resistant properties. The chromium enables stainless steel to form a tough oxide film as soon as, and for as long as, it's exposed to oxygen, even while submerged, provided that the water contains oxygen; nickel increases its resistance to acid. Depending upon the role it's called upon to fill-architectural trim, cutlery, or bow rail, for instance-differing amounts of elements are added, along with trace amounts of still more exotic materials, such as columbium and tantalum.