Cast iron, like steel and wrought iron, is an alloy consisting primarily of iron and carbon but has a carbon content usually in the range of 2- 4%, which appears as flakes of graphite intermixed within the material. Commonly, when cast iron is submerged in a marine environment, the iron component corrodes away, leaving behind the graphite along with iron corrosion products. Iron in this state is often referred to as ‘graphitized’. Fortunately, even though the iron has corroded away, the shapes of cast iron objects recovered from marine sites often remain intact due to the surviving graphite holding the iron corrosion products in situ.
To help illustrate the difference between non-corroded cast iron and graphitized cast iron, last week we x-rayed the damping piston valve cover next to one of its copies cast at the Buffalo State College Foundry.