Steel and iron are often referred to interchangeably because they have similar characteristics. Iron is a metal, and steel is a manmade alloy that mixes iron with carbon and other elements. Both are hard and resilient with a wide temperature range and corrosion resistance in high-humidity environments. Steel is widely used in construction for carrying water, flammable gases, and in fire sprinkler systems. Black steel, or black malleable iron, is made from corrosion-resistant ungalvanized steel. Zinc galvanized steel has a zinc coating that resists rust, corrosion, mineral buildup, and wet conditions. Grooved ductile iron is lighter, stronger, and more durable than cast iron. Uncoated alloy steels, also called chrome-moly, are stronger than carbon steel and resist rupturing. Ductile iron service saddles reinforce and support the addition of branch lines or service connections on new or existing pipe.