Grey cast iron is usually just referred to as cast iron or grey iron which is used in several different products such as flywheels and engine blocks. Grey cast iron gets its name from the grey color which comes from tiny graphite flakes used in its composition which helps protect against corrosion. Grey cast iron has been used since 1770's when they made bridges out of cast iron, textile plants
. and building back then used cast iron as well. Even though bridges and such no longer use a lot of this material there are still many manufactures and products that do use grey cast iron for example manhole covers are made from it. For more information take a look at this page http://en.wikipedia.org/wiki/Cast_iron