Types of Stainless Steel

To distinguish different types of stainless steel, we measure the metal’s microstructure at room temperature to learn more about the overall composition. In total, there are five primary types of stainless steel:


With a similar structure to low alloy steels, ferritic stainless steel boasts strong resistance to corrosion cracking. Using little to no nickel — one of the priciest alloying elements — it’s less expensive than austenitic steel, and typically has a significant percentage of chromium (11.2% – 19%). However, it is also less formable than austenitic steel. Finally, ferritic steel is magnetic.


This is the most common variety of stainless steel, making up more than 70% of overall production. It’s a well-rounded structure, with adequate weldability, formability, and creep resistance. Unlike ferritic steel, austenitic varieties are for all intents and purposes non-magnetic. Austenitic steel gets its name from the crystalline microstructure, which is made of isometric crystals. When you add a large proportion of molybdenum (over 6%), the steel becomes superaustenitic, which gives it better protection against crevice corrosion and cracking.


This stainless steel type contains chromium, nickel, molybdenum, and carbon, which makes for a more brittle microstructure. However, it is generally tougher than the austenitic and ferritic varieties. Though they have relatively low formability, these alloys can be tempered as you would with carbon steels. Adding a small amount of nickel improves the martensitic steel’s lack of weldability.


These hybrid alloys are called duplex because the composition is about 50% austenitic and 50% ferritic. By combining the two microstructures, you end up with a new form that has more strength than both. The strong composition also leads to improved corrosion resistance and stress cracking resistance. Since duplex steel has such a large proportion of ferritic alloy, this type is also magnetic.

Precipitation Hardening

Finally, this martensitic type has been made even stronger by adding aluminum, copper, and niobium, in conjunction with a precipitation hardening process. It involves heat-treating the metal to create particles in the crystal lattice, which help to stop irregularities in the microstructure and boost the alloy’s overall strength.

Carbon Steel vs Stainless Steel

Carbon and stainless steel are both created with percentages of carbon and iron, but their characteristics are fairly distinct. Below, we’ve outlined the benefits and drawbacks of each alloy.

Carbon Steel

This is the most basic form of steel available. A tiny proportion of carbon is added to drastically improve the metal’s hardness, but it also makes the carbon steel less ductile. Typically, the percentage of carbon in this steel is much higher than in stainless steel, and it largely defines how the metal behaves. Any other alloying elements — such as manganese, tungsten, or chromium — have a smaller effect on the carbon steel’s overall properties.

That being said, carbon steel still makes up around 90% of today’s steel production. It can be used to make a wide range of products, such as automobile parts, structural beams, knives, steel wires, and refrigerator parts. The alloy is susceptible to corrosion, so it needs to be galvanized for outdoor use. It’s also not nearly as attractive as stainless steel, with a dull, uninspiring finish. Overall, the higher carbon content increases the metal’s durability, heat distribution, and malleability, but it also lowers its melting point.

Stainless Steel

On a superficial level, stainless steel is an attractive metal, with a lustrous and reflective finish that is easy on the eyes. This is due to the high percentage of chromium (over 10.5%) in the alloy, which changes its appearance and also helps to prevent corrosion. Unlike carbon steel, stainless steel has a chromium oxide coating that protects against rust and stains. Some stainless steel alloys are even resistant to sulfuric or phosphoric acid.

You’ll find stainless steel in countless applications, including handrails, cutlery, razor blades, hot water tanks, medical instruments, jewelry, and many others. During the Art Deco period, stainless steel was hugely influential in creating decorative and structural elements that we revere today. However, stainless steel is heavier than carbon steel and aluminum, with the lowest strength-to-weight ratio. That makes it unsuitable for aviation and other industries where weight is a critical factor.

Overall, stainless steel’s decorative and rust-resistant properties make it the clear winner for many people, but carbon steel is still the preferred metal for manufacturing and construction purposes.