Gray iron is a versatile, low-cost alloy with a long history and many manufacturing applications. Gray iron's high carbon content gives it a dull, gray appearance with low reflectivity. Common uses for gray cast iron include pipes, cookware and automobile parts.
Gray iron's high carbon content makes it easy to melt, weld, machine and cast using common metalworking processes. Gray iron contains graphite flakes that provide a high level of stability and minimize shrinking during the casting process. The metallurgy of gray iron also makes it resistant to corrosion. Gray iron's high conductivity makes it ideal for cookware.
Gray cast iron's extremely low tensile strength makes it a poor shock resistor relative to newer, less rigid iron alloy varieties. Blasting gray iron can weaken castings by causing residual stress. Gray iron may be too brittle for some applications, including instances when a casting must be especially thin or flexible.
Gray iron's density makes it excellent for some applications, but inappropriate for others. For example, high density gray cast iron is an excellent choice for pipes, but a cast iron bicycle would be too heavy and too rigid to ride safely.