Oxidation of Different Types of Cast Iron
Cast iron is a form of iron that is composed of a variety of different metals and alloys. These materials can be divided into three broad categories: grey, white, and malleable iron. Each type of cast iron has its own advantages and drawbacks, depending on the application the material is intended for. In this article, we will explore the oxidation behaviour of the three common types of cast iron and its impact on their properties.
Grey or gray cast iron is a popular choice for applications where wear and tear resistance is needed. This particular type of cast iron is composed of 2% to 4% carbon and 1% to 3% silicon, along with smaller amounts of manganese and sulphur. The silicon content in grey cast iron helps to create a flake-like structure in its microstructure. This flake graphite structure helps to promote the lubricating properties of grey cast iron and prevents it from wearing down too quickly.
Unfortunately, this flake graphite structure also makes grey cast iron more susceptible to oxidation than other types of cast iron. The oxidation process can cause the surface of the cast iron to become rough, reducing its ability to resist wear and corrosion and promoting rusting. To reduce the oxidation of grey cast iron and help protect it from wear and corrosion, it must be kept in an environment where it is shielded from oxygen and humid conditions and given regular protective coatings or other types of treatments.
White cast iron is another type of cast iron that is composed primarily of iron and large amounts of carbon, with other minor elements such as nickel and chromium added to increase its toughness.White cast iron also contains some silicon, which is why it has a slightly gray color. Unlike gray cast iron, white cast iron has a more uniform microstructure with no flake graphite, giving it greater ductility and wear resistance. This also makes it less susceptible to oxidation.
Malleable iron is a third type of cast iron that has been processed to reduce its hardness and increase its ductility. It is composed of a base of iron with 1.5% to 5% carbon and small amounts of silicon, manganese, and other elements. Since malleable iron has a much more uniform microstructure than gray and white cast iron, it is much less susceptible to oxidation. This type of cast iron is able to withstand greater amounts of wear and tear and still maintain its form and protective coating.
Because of the wide range of compositions and microstructures of different types of cast iron, their susceptibility to oxidation can vary greatly. Grey cast iron is the most susceptible to oxidation, while white cast iron and malleable iron are less so. To protect cast iron from oxidation and keep it in good condition, it should be kept in an environment that is protected from oxygen and moisture, and it should be given regular protective coatings or treatments.
