![]() ![]() Moreover, if the surface is damaged, the exposed steel will react with the atmosphere to self-repair and regenerate the oxide, the "passivation film," for resumed protection. This oxide film is so thin as to only a few microns through the chrome the natural luster of the surface can be seen, hence the stainless steel has a unique surface. As the chromium contained reaches 12%, the stainless steel reacted with the atmosphere will produce a passivation film (Cr2O3) on the surface, a dense chromium-rich oxide that effectively protects the stainless steel surface from further oxidation. ![]() The “stainless” property is related to the chromium contained within the steel. Stainless steel, in contrast is corrosion resistant. Ordinary carbon steel reacts with oxygen of the atmosphere to form an oxide film on the metal surface and keeps oxidizing, which results in expanded rust, forming a "thousand-layer Cake" type of corrosion until the rotten wear. Why Stainless Steel is Corrosion Resistance? On the contrary, if the compounds are unstable, volatile or dissolved, not bonding with the metal strongly, the corrosion products will be peeling off layer by layer, like the oxide, hence unable to protect the metal matrix from further corrosion. This behavior is known as "passivation effect." If the compounds produced by the chemical corrosion are stable, not easy to evaporate and dissolve, of dense tissue and binding strongly with metal matrix, the corrosion products will stay attached to the metal surface to form a passivation layer, hence to protect the metal matrix from further corrosion. The chemical corrosion product exists on the metal surface, without any current being generated during the corrosion process. ![]() The corrosion is known as chemical corrosion. When metal is exposed to and reacts with the dry gas and nonelectrolyte solution, it will produce corrosion. British usage of stainless steel and inox steel, ngrams shows little difference between the corpuses, and in both cases inox has nearly no usage compared with stainless steel: Wikipedia includes part of a 1915 New York Times article that refers to "a stainless steel" that is "claimed to be non-rusting, unstainable, and untarishable" which at least partly confutes the "stains less" etymology of stainless steel, which is suggested in the link in the question. For example, after a stainless steel surface is cleaned with steel wool rather than brass wool, it may develop rust stains.Įtymonline gives a 1917 date of origin of the term and says stainless steel is "so called because it is highly resistant to rust or tarnish." Edit: tabulates definitions of stainless steel from a dozen sources, two etymology references, and several audio links. The treatment is followed by rinsing, first with drinking water and then with demineralised water.Wikipedia says of stainless steel that stainless steel is "also known as inox steel or inox from French inoxydable".Īs is well known, and mentioned in Wikipedia, stainless steel stains less easily and rusts or corrodes less easily, than ordinary steel, but it is not stain-proof and in some conditions can rust or corrode or give such appearance. Analysis of the iron content and acid concentrations determine when the treatment is complete. The duration of this treatment depends on the type of stainless steel and the temperature. The passivation fluid is circulated through the installation or system using acid-resistant pump units. The pickling treatment results in a chrome-rich surface.Īlthough the stainless steel will spontaneously passivate after pickling (forming a protective chromium oxide film) by exposure to sufficient oxygen in the outside air, closed systems are generally chemically passivated. After pickling, the material is rinsed with low-chloride water to remove acid residues. The pickling treatment removes iron particles and other contaminants from previous treatments on the material such as welding, handling, etc. ![]() Degreasing is necessary to remove oil, grease and atmospheric contamination and to make the surface optimally accessible for the pickling agent. Pre-commissioning cleaning of austenitic stainless steel generally involves three steps: degreasing, pickling and passivating. ![]()
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