8/10/2023 0 Comments Steel s![]() The corrosion resistance of iron-chromium alloys was first recognized in 1821 by French metallurgist Pierre Berthier, who noted their resistance against attack by some acids and suggested their use in cutlery. Unlike stainless steel, however, these artifacts owe their durability not to chromium but to their high phosphorus content, which, together with favorable local weather conditions, promotes the formation of a solid protective passivation layer of iron oxides and phosphates, rather than the non-protective cracked rust layer that develops on most ironwork. A famous example is the Iron Pillar of Delhi, erected by order of Kumara Gupta I around AD 400. Passivation occurs only if the proportion of chromium is high enough and oxygen is present.Ī few corrosion-resistant iron artifacts survive from antiquity. Stainless steels contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion by blocking oxygen diffusion to the steel surface and blocks corrosion from spreading into the metal's internal structure, and, due to the similar size of the steel and oxide ions, they bond very strongly and remain attached to the surface. This iron oxide film (the rust) is active and accelerates corrosion by forming more iron oxide and, because of the greater volume of the iron oxide, this tends to flake and fall away. ![]() Unprotected carbon steel rusts readily when exposed to air and moisture. Stainless steel differs from carbon steel by the amount of chromium present. Stainless steel is used where both the properties of steel and corrosion resistance are required. There are different grades and surface finishes of stainless steel to suit the environment the alloy must endure. ![]() Stainless steel does not readily corrode, rust or stain with water as ordinary steel does but, despite the name, it is not fully stain-proof, most notably under low-oxygen, high-salinity, or poor-circulation environments. In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is a steel alloy with a minimum of 10.5% chromium content by mass.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |