Stainless steel
Stainless steel's resistance to corrosion results from the 10.5%, or more, chromium content which forms a passive film that can protect the material and self-heal in the presence of oxygen.
[6] Thus, there are numerous grades of stainless steel with varying chromium and molybdenum contents to suit the environment the alloy must endure.
[7] Corrosion resistance can be increased further by the following means: The most common type of stainless steel, 304, has a tensile yield strength around 210 MPa (30,000 psi) in the annealed condition.
Nevertheless, stainless steel connectors are employed in situations where ECR poses a lower design criteria and corrosion resistance is required, for example in high temperatures and oxidizing environments.
[13] Grades with low coercive field have been developed for electro-valves used in household appliances and for injection systems in internal combustion engines.
[14] Galling, sometimes called cold welding, is a form of severe adhesive wear, which can occur when two metal surfaces are in relative motion to each other and under heavy pressure.
Under high contact-force sliding, this oxide can be deformed, broken, and removed from parts of the component, exposing the bare reactive metal.
The invention of stainless steel followed a series of scientific developments, starting in 1798 when chromium was first shown to the French Academy by Louis Vauquelin.
In the early 1800s, British scientists James Stoddart, Michael Faraday, and Robert Mallet observed the resistance of chromium-iron alloys ("chromium steels") to oxidizing agents.
[26][27] In 1908, the Essen firm Friedrich Krupp Germaniawerft built the 366-ton sailing yacht Germania featuring a chrome-nickel steel hull, in Germany.
[28] On 17 October 1912, Krupp engineers Benno Strauss and Eduard Maurer patented as Nirosta the austenitic stainless steel[29][30][31][28] known today as 18/8 or AISI type 304.
[32] Similar developments were taking place in the United States, where Christian Dantsizen of General Electric[32] and Frederick Becket (1875–1942) at Union Carbide were industrializing ferritic stainless steel.
[18] The metal was later marketed under the "Staybrite" brand by Firth Vickers in England and was used for the new entrance canopy for the Savoy Hotel in London in 1929.
Brearley and Haynes pooled their funding and, with a group of investors, formed the American Stainless Steel Corporation, with headquarters in Pittsburgh, Pennsylvania.
[37] As late as 1932, Ford Motor Company continued calling the alloy "rustless steel" in automobile promotional materials.
Their mixed microstructure provides improved resistance to chloride stress corrosion cracking in comparison to austenitic stainless steel types 304 and 316[citation needed].
The properties of duplex stainless steels are achieved with an overall lower alloy content than similar-performing super-austenitic grades, making their use cost-effective for many applications.
More recently, the less expensive (and slightly less corrosion-resistant) lean duplex has been developed, chiefly for structural applications in building and construction (concrete reinforcing bars, plates for bridges, coastal works) and in the water industry.
Uniform corrosion takes place in very aggressive environments, typically where chemicals are produced or heavily used, such as in the pulp and paper industries.
Good design, fabrication techniques, alloy selection, proper operating conditions based on the concentration of active compounds present in the solution causing corrosion, pH, etc.
[73] Standard mill finishes can be applied to flat rolled stainless steel directly by the rollers and by mechanical abrasives.
[78] Electric arc welding of type 430 ferritic stainless steel results in grain growth in the HAZ, which leads to brittleness.
This has largely been overcome with stabilized ferritic grades, where niobium, titanium, and zirconium form precipitates that prevent grain growth.
[80][81] Duplex stainless steel welding by electric arc is a common practice but requires careful control of the process parameters.
Other welding processes include: Stainless steel may be bonded with adhesives such as silicone, silyl modified polymers, and epoxies.
The interest rate (i) is used to convert expenses from different years to their present value (a method widely used by banks and insurance companies) so they can be added and compared fairly.
Note that stainless steel produced in countries that use cleaner sources of electricity (such as France, which uses nuclear energy) will have a lower carbon footprint.
[89][90] An average stainless steel object is composed of about 60% recycled material of which approximately 40% originates from end-of-life products, while the remaining 60% comes from manufacturing processes.
The fourth step is the collection of stainless steel for recycling at the end of life of the goods (such as kitchenware, pulp and paper plants, or automotive parts).
However, during cooking, small amounts of nickel and chromium leach out of new stainless steel cookware into highly acidic food.
