After carbon steel, SS is most widely used material in Process industries because of
its excellent corrosion resistance property.
• Stainless steel is a steel with a minimum chromium content of 10.5 % or more, and a
maximum carbon content of less than 1.20% • Stainless steel has excellent resistant
to corrosion and good ductility • Stainless steel becomes corrosion resistant
due to formation of non-reactive chromium oxide (Cr2O3) film that adheres tightly to
the surface of metal.
This film acts as a barrier, and protec metal against corrosion.
• There are different types of SS used in industries.
Based on micro structure ss can be classified as
• Austenitic stainless steel, which − is Non Magnetic in nature & has very High
Corrosion resistance − these types of SS are widely use in process
industry and a variety of industrial applications , cookware are also manufactured from Austenitic
stainless steel − Type 304, 304L,316,316L are example of
Austenitic stainless steel • Ferritic stainless steel is
− Magnetic & Contains high carbon, therefore brittle & relatively poor corrosion resistance
− But it Has a resistance to chlorides stress corrosion cracking so it's used in marine,
petrochemical, heat exchangers, furnaces application − Type 409, 430, 439 are example of Ferritic
stainless steel • Martensitic stainless steel
− Has High hardness & Poor Corrosion resistant − It Used in manufacturing of sport knives
and multi-purpose tools − Type 410,420 are example of Martensitic
stainless steel • Precipitation Hardened stainless steel
− Are Heat treatable to high strength, it has Very high strength-to-weight ratio with
good corrosion resistance − It used in making aerospace components
and springs − 17-7PH, 17-4PH are example of Precipitation
Hardened stainless steel • Duplex & Super Duplex stainless steel
− Contain both Austenite & Ferrite in microstructure − It Offer benefits of both Austenite & Ferrite
stainless steel − It has Good resistance to pitting and
crevice corrosion hence − Used in sea water system, heat exchanger,
structural application − EX- UNS S32205, S31803, S32760 are example
of Duplex & Super Duplex stainless steel • Let's summaries what you have learned
in this lecture • You learned What is Stainless Steel is
• Properties of Stainless Steel & • Types of Stainless steel
See you in the next lecture.
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