In Metallurgy, stainless steel – also known as “inox steel” – is defined as an alloy steel with a minimum of 10.5 – 11% chromium.
Stainless steel does not corrode, rust or stain when in contact with water, as does ordinary steel. Despite the name “inox” (as in “inoxidizable”), it is not entirely oxidation-proof.
There are varying degrees of classification and types of finishes on stainless steel surfaces, whose alloy must withstand and adapt to the environment where it is applied. Stainless steel is applied where both the mechanical properties of steel as well as corrosion resistance are required.
Stainless steel differs from carbon steel due to the chromium content present in the material. It contains enough chromium to form a passive layer of chromium oxide, which serves to ensure that any corrosion remains only in this superficial layer and will not spread, affecting the internal structure of the metal.
Alloy Steel is steel that is alloyed with a variety of elements totaling between 3.0% and 12.0%, to improve its mechanical and chemical properties. Alloy steels are divided into two groups: low-alloy steel and high-alloy steel.
Duplex stainless steel has a mixed microstructure of Austenite and Ferrite, the aimed at obtaining a microstructure with a content of 50% of each. However, in commercial alloys, this proportion can be 40/60. This material is roughly twice as corrosion-resistant, when compared to austenitic stainless steel, particularly pitting corrosion, crevice corrosion, and stress corrosion. These materials are characterized by a high chromium content (19–32%), molybdenum (up to 5%), and a lower nickel content than austenitic stainless steel.
The high chromium and molybdenum content in Super Duplex materials makes them extremely resistant to uniform corrosion when subjected to media containing organic acids, such as formic and acetic acids. Super Duplex also offers excellent resistance against inorganic acids, especially ones containing chlorides.
Krominox offers solutions for applications that require special alloys of forged metals, with superior properties, mechanical strength, resistance to corrosion, wear and heat, and/or high conductivity. This includes: alloys forged at elevated temperatures in carbon steel, Super Duplex stainless, forged nickel and titanium alloys, Inconel, special non-ferrous alloys, among others.