Austenitic stainless steels are non-magnetic. In addition to containing 18% chromium, they also have a minimum of 8% nickel, which enhances their corrosion resistance. This resistance is further improved by alloying with molybdenum, which helps form a stable protective passivation oxide layer for additional protection. These steels are also characterized by excellent toughness and the ability to maintain their mechanical properties even at very low temperatures.

Ferritic stainless steels are magnetic and have a low carbon content. Their main alloying element is chromium (typically between 13% and 17%), and nickel is not added. Their primary advantage is resistance to stress-corrosion cracking and atmospheric corrosion. They are also relatively inexpensive. However, special precautions must be taken before, during, and after fusion welding.

Martensitic stainless steels have a ferritic structure in the annealed condition and a martensitic structure when quenched and tempered. Compared to conventional martensitic steel grades, they offer improved corrosion resistance. These steels contain between 12% and 15% chromium and between 0.1% and 0.5% carbon. The addition of molybdenum further enhances their corrosion and wear resistance. Steels with 0.1% to 0.25% carbon are primarily used in constructions requiring both corrosion resistance and enhanced mechanical properties. Meanwhile, steel grades with 0.3% carbon or more are used for cutting tools due to their high hardness and superior wear resistance.

Precipitation-hardened stainless steels are iron-chromium-nickel alloys characterized by high strength, achieved through the precipitation hardening of their austenitic or martensitic structure. This process allows for alloying with one or more elements, such as copper, aluminum, titanium, niobium, and molybdenum.

Duplex stainless steels have a characteristic austenitic-ferritic microstructure, typically in a 50:50 ratio (commercial grades). They contain approximately 22% chromium and 5% nickel and are additionally alloyed with molybdenum and nitrogen. These steels exhibit excellent mechanical properties, particularly high yield strength and tensile strength. They are partially magnetic and offer strong resistance to pitting and stress-corrosion cracking.