The Difference Between Carbon and Stainless Steel

Choosing the right type of steel for your project is one of the most important decisions. However, before deciding on individual grades, you must first decide which type of steel to use, such as carbon steel or stainless steel.
Carbon and stainless steel belong to one principal, both are steels. Steel containing only carbon elements is called carbon steel, while stainless steel is steel with high alloy content added for rust resistance.
Stainless steel is an alloy that is resistant to corrosion by weakly corrosive media such as air, steam and water and chemically aggressive media such as acids, alkalis and salts. Carbon steel is an iron-carbon alloy containing less than 2.11% carbon, also known as carbon steel, which is much harder than stainless steel, but heavier, less plastic, typically “too rigid and easy to break”, easy to rust.

The Differences Between Carbon and Stainless Steel Include:

Corrosion resistance
Mechanical properties
External appearance
Cost

Corrosion Resistance of Carbon and Stainless Steel

The most obvious difference between carbon steel and stainless steel is the ability to resist corrosion. As the name implies, stainless steel is usually the more corrosion resistant of the two. Both carbon and stainless steel contain iron, which oxidises when exposed to the environment, producing rust. The addition of chromium to stainless steel makes it more resistant to corrosion than carbon steel.
Chromium will adhere to oxygen more readily than iron. When chromium adheres to oxygen it creates a chromium oxide layer that protects the rest of the material from degradation and corrosion. Carbon steels usually do not have enough chromium to form this chromium oxide layer, allowing oxygen to combine with iron, which can lead to iron oxide or rusting. Therefore, if corrosion resistance is a key factor, then stainless steel is the way to go.

Mechanical Properties

It is difficult to make a comprehensive statement on the differences in mechanical properties between carbon and stainless steels, as there are many different types and grades of carbon and stainless steel. Stainless steels may be more ductile than carbon steels as they usually contain more nickel.
However, there are also very brittle grades of stainless steel, such as martensitic grades. Carbon steels with very low carbon content may not match the tensile strength of some stainless steels because many stainless grades contain alloying elements that increase their strength. However, if there is sufficient carbon in the carbon steel (usually at least 0.30 wt%), it is easier to heat treat than austenitic stainless steels.

Appearance

If the job requires aesthetic appeal, the appearance of the metal must be considered. When appearance is a factor, stainless steel with a specific finish is usually preferred. While both can be sanded and polished for a bright, shiny appearance, carbon steel requires a varnish or paint fairly quickly after the polishing process.
If not applied, carbon steel will begin to discolour and eventually rust.Moreover, during the smelting and forging of carbon steel, defects in the steel can be caused by equipment and process operations, etc., which generally include scarring, white spots, loosening, non-metallic inclusions, etc. In addition, if stainless steel is scratched it will retain its lustre in the scratched area, whereas a painted carbon steel piece will need to be repainted or it will suffer from corrosion.

Cost

Another important consideration is the difference in cost between carbon steel and stainless steel. Although the cost varies between grades, stainless steel is usually more expensive than carbon steel. This is mainly due to the various alloying elements added to stainless steel, including chromium, nickel and manganese.
These additional elements all add up to an increased cost compared to carbon steel. Carbon steel, on the other hand, consists mainly of relatively affordable elements of iron and carbon. If you are on a tight budget for your next project, carbon steel may be the best choice.

How Do We Choose Between Carbon and Stainless Steel?

Choosing between carbon steel and stainless steel for a particular job will involve weighing up all these factors and considering them carefully. If the metal is to be hidden from view, then there is no point in spending extra money on stainless steel strictly on the basis of its appearance.
However, if it is to be hidden from view but subjected to a corrosive environment, then stainless steel may actually be the best choice. Stainless steel is more expensive than carbon steel due to the large number of other alloys that need to be added in the process of making it, whereas carbon steel does not require the addition of a large number of other alloys.Ultimately, the choice will depend on the specifics of the job or project.

In addition, it must be welded with a welding rod or wire that matches the carbon and stainless steel. It is recommended that stainless steel and carbon steel are not welded together, because after the two are welded together, after the oxidation of air, there will be a carburization reaction, which will have an effect on the stainless steel.

Shandong Baowu Steel Group.

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