Stainless Steel vs Carbon Steel
Stainless steel and carbon steel are iron alloys, which fall under the category of steel. Steels contain carbon up to 2% by weight. Stainless steel and carbon steel can be differentiated by their alloying elements and their compositions.
As the name implies, stainless steel is resistant to corrosion, unlike other steels. In stainless steel, the chromium percentage is at least 10.5% by weight. The corrosion resistance of stainless steel is due to the high amount of chromium present in this steel. Chromium forms an invisible, thin and adherent oxide layer, which makes the surface passive. To form this passive oxide layer, steel should contain enough chromium and should be in an oxygen rich environment. This passive layer protects the metal beneath, by covering it from air and water. Also, if the oxide layer is scratched, it heals itself. Because of this, the chromium percentage in stainless steel should exceeds more than 10.5% by weight. Other than chromium and carbon, stainless steel contains Silicon, Phosphorous, Manganese, sulfur, Nickel and Molybdenum. Typically, stainless steel contains carbon in the range of 0.03 – 1% by weight. If the carbon content increases to more than that, it may reduce the stainless property of this steel by making Cr23C6, and lessening Chromium make the passive oxide layer. Stainless steels can also be classified as Austenitic, Ferritic, Martensitic, Precipitation-Hardening, Duplex and Cast according to their crystalline structure. Due to some of the alloying elements, stainless steel can become non-magnetic.
Other than the stainless steel, all the other steels are carbon steels. Carbon steel contains up to 2% carbon, up to 1.65% Manganese, up to 0.6% Silicon and up to 0.6% copper by weight. Depending on the carbon content, carbon steel can be further classified into low carbon steel, medium carbon steel, and high carbon steel. Carbon steel is less corrosion resistant than stainless steel. Because of this, they should not be used in corrosive atmospheres or else they can be coated with a protective layer. Carbon steels are cheaper than stainless steels as its main alloying element is carbon, while the relatively expensive chromium is stainless steels’ main alloying element. Carbon steel becomes stronger and harder with the increasing content of carbon, but it lessens the ductility. The required mechanical properties of carbon steel can be changed by heat treating.
Stainless steel and carbon steel are used for many applications like skyscrapers, bridges, aviation industry, mining, offshore industry, pipes etc. Both are ductile materials and are sometimes used for decorative purposes. Depending on the alloying elements and their composition, their properties vary readily. Therefore, stainless steel or carbon steel must be selected as to the requirement of the application.
What is the difference between Stainless Steel and Carbon Steel?
• The main alloying element in carbon steel is carbon while it is chromium in stainless steel.
• Stainless steel is resistant to corrosion, but carbon steel has poor resistance to corrosion.
• Stainless steel is more expensive than carbon steel.
• Carbon steel is magnetic, but some of the stainless steels are not magnetic.
• Normally in stainless steel carbon content is between 0.03 – 1% by weight, but in carbon steel it is up to 2%.