Chromium in the context of Corrosion

Corundum is a crystalline form of aluminium oxide (Al₂O₃) typically containing traces of iron, titanium, vanadium, and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink-orange.

The name "corundum" is derived from the Tamil-Dravidian word kurundam (ruby-sapphire) (appearing in Sanskrit as kuruvinda).

The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The composition of the solar wind plasma also includes a mixture of particle species found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron. There are also rarer traces of some other nuclei and isotopes such as phosphorus, titanium, chromium, and nickel's isotopes Ni, Ni, and Ni. Superimposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface.

At a distance of more than a few solar radii from the Sun, the solar wind reaches speeds of 250–750 km/s and is supersonic, meaning it moves faster than the speed of fast magnetosonic waves. The flow of the solar wind is no longer supersonic at the termination shock. Other related phenomena include the aurora (northern and southern lights), comet tails that always point away from the Sun, and geomagnetic storms that can change the direction of magnetic field lines.

Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to its high elastic modulus, yield strength, fracture strength and low raw material cost, steel is one of the most commonly manufactured materials in the world. Steel is used in structures (as concrete reinforcing rods or steel beams), in bridges, infrastructure, tools, ships, trains, cars, bicycles, machines, electrical appliances, furniture, and weapons.

Iron is always the main element in steel, but other elements are used to produce various grades of steel, demonstrating altered material, mechanical, and microstructural properties. Stainless steels, for example, typically contain 18% chromium and exhibit improved corrosion and oxidation resistance versus their carbon steel counterpart. Galvanized steel is coated in a layer of zinc to achieve a similar effect. Under atmospheric pressures, steels generally take on two crystalline forms: body-centered cubic and face-centered cubic; however, depending on the thermal history and alloying, the microstructure may contain the distorted martensite phase or the carbon-rich cementite phase, which are tetragonal and orthorhombic, respectively. In the case of alloyed iron, the strengthening is primarily due to the introduction of carbon in the primarily-iron lattice, inhibiting deformation under mechanical stress. Alloying may also induce additional phases that affect the mechanical properties. In most cases, the engineered mechanical properties are at the expense of the ductility and elongation of the pure iron state, which decrease upon the addition of carbon.

Serpentine subgroup (part of the kaolinite-serpentine group in the category of phyllosilicates) are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos, and as decorative stone. The name comes from the greenish color and smooth or scaly appearance from the Latin serpentinus, meaning "snake-like".

Serpentine subgroup is a set of common rock-forming hydrous magnesium iron phyllosilicate ((Mg,Fe)
₃Si
₂O
₅(OH)
₄) minerals, resulting from the metamorphism of the minerals that are contained in mafic to ultramafic rocks. They may contain minor amounts of other elements including chromium, manganese, cobalt or nickel. In mineralogy and gemology, serpentine may refer to any of the 20 varieties belonging to the serpentine subgroup. Owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine: antigorite, lizardite and chrysotile.

In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the refractory metals, which are elemental metals and their alloys that have high melting temperatures.

Refractories are defined by ASTM C71 as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F (811 K; 538 °C)". Refractory materials are used in furnaces, kilns, incinerators, and reactors. Refractories are also used to make crucibles and molds for casting glass and metals. The iron and steel industry and metal casting sectors use approximately 70% of all refractories produced.

Chromate salts contain the chromate anion, CrO2−4. Dichromate salts contain the dichromate anion, Cr₂O2−7. They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible.

Stainless steel is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Alternatively, it is known as inox (an abbreviation of the French term inoxydable, meaning non-oxidizable), corrosion-resistant steel (CRES), Nirosta (an abbreviation of the German term nichtrostender Stahl) or rustless steel. Stainless steel's resistance to corrosion comes from its chromium content of 10.5% or more, which forms a passive film that protects the material and can self-heal when exposed to oxygen. It can be further alloyed with elements like molybdenum, carbon, nickel and nitrogen to enhance specific properties for various applications.

The alloy's properties, such as luster and resistance to corrosion, are useful in many applications. Stainless steel can be rolled into sheets, plates, bars, wire, and tubing. These can be used in cookware, cutlery, surgical instruments, major appliances, vehicles, construction material in large buildings, industrial equipment (e.g., in paper mills, chemical plants, water treatment), and storage tanks and tankers for chemicals and food products. Some grades are also suitable for forging and casting.

Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495–570 nm. In subtractive color systems, used in painting and color printing, it is created by a combination of yellow and cyan; in the RGB color model, used on television and computer screens, it is one of the additive primary colors, along with red and blue, which are mixed in different combinations to create all other colors. By far the largest contributor to green in nature is chlorophyll, the chemical by which plants photosynthesize and convert sunlight into chemical energy. Many creatures have adapted to their green environments by taking on a green hue themselves as camouflage. Several minerals have a green color, including the emerald, which is colored green by its chromium content.

During post-classical and early modern Europe, green was the color commonly associated with wealth, merchants, bankers, and the gentry, while red was reserved for the nobility. For this reason, the costume of the Mona Lisa by Leonardo da Vinci and the benches in the British House of Commons are green while those in the House of Lords are red. It also has a long historical tradition as the color of Ireland and of Gaelic culture. It is the historic color of Islam, representing the lush vegetation of Paradise. It was the color of the banner of Muhammad, and is found in the flags of nearly all Islamic countries.

A mordant or dye fixative is a substance used to set (i.e., bind) dyes on fabrics. It does this by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in cell or tissue preparations. Although mordants are still used, especially by small batch dyers, they have been largely displaced in industry by substantive dyes.

The term mordant comes from the Latin mordere, "to bite". In the past, it was thought that a mordant helped the dye "bite" onto the fiber so that it would hold fast during washing. A mordant is often a polyvalent metal ion, and one example is chromium (III). The resulting coordination complex of dye and ion is colloidal and can be either acidic or alkaline.

A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native deposits singly or in alloys include antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, molybdenum, nickel, niobium, rhenium, tantalum, tellurium, tin, titanium, tungsten, vanadium, and zinc, as well as the gold group (gold, copper, lead, aluminium, mercury, silver) and the platinum group (platinum, iridium, osmium, palladium, rhodium, ruthenium). Among the alloys found in native state have been brass, bronze, pewter, German silver, osmiridium, electrum, white gold, silver-mercury amalgam, and gold-mercury amalgam.

Only gold, silver, copper and the platinum group occur native in large amounts. Over geological time scales, very few metals can resist natural weathering processes like oxidation, so mainly the less reactive metals such as gold and platinum are found as native metals. The others usually occur as isolated pockets where a natural chemical process reduces a common compound or ore of the metal, leaving the pure metal behind as small flakes or inclusions.

Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or mechanical loads. Inconel alloys are oxidation- and corrosion-resistant. When heated, Inconel forms a thick, stable passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, making it attractive for high-temperature applications in which aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies. Inconel's high-temperature strength is developed by solid solution strengthening or precipitation hardening, depending on the alloy.

Inconel alloys are typically used in high temperature applications. Common trade names for various Inconel alloys include:

Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al₂O₃) with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name sapphire is derived from the Latin word sapphirus, itself from the Greek word sappheiros (σάπφειρος), which referred to lapis lazuli. It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. Red corundum stones also occur, but are called rubies rather than sapphires. Pink-colored corundum may be classified either as ruby or sapphire depending on the locale. Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third-hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of special-purpose solid-state electronics such as integrated circuits and GaN-based blue LEDs. It occurs in association with ruby, zircon, biotite, muscovite, calcite, dravite and quartz.

Vanadium is a chemical element; it has symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) somewhat stabilizes the free metal against further oxidation.

Spanish-Mexican scientist Andrés Manuel del Río discovered compounds of vanadium in 1801 by analyzing a new lead-bearing mineral he called "brown lead". Though he initially presumed its qualities were due to the presence of a new element, he was later erroneously convinced by French chemist Hippolyte Victor Collet-Descotils that the element was just chromium. Then in 1830, Nils Gabriel Sefström generated chlorides of vanadium, thus proving there was a new element, and named it "vanadium" after the Scandinavian goddess of beauty and fertility, Vanadís (Freyja). The name was based on the wide range of colors found in vanadium compounds. Del Río's lead mineral was ultimately named vanadinite for its vanadium content. In 1867, Henry Enfield Roscoe obtained the pure element.

Ruby is a pinkish-red to blood-red gemstone, a variety of the mineral corundum (aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires; given that the rest of the corundum species are called as such, rubies are sometimes referred to as "red sapphires".

Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire, emerald, and diamond. The word ruby comes from ruber, Latin for red. The color of a ruby is due to the presence of chromium.

In physical chemistry and engineering, passivation is coating a material so that it becomes "passive", that is, less readily affected or corroded by the environment. Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material, or allowed to build by spontaneous oxidation in the air. As a technique, passivation is the use of a light coat of a protective material, such as metal oxide, to create a shield against corrosion. Passivation of silicon is used during fabrication of microelectronic devices. Undesired passivation of electrodes, called "fouling", increases the circuit resistance so it interferes with some electrochemical applications such as electrocoagulation for wastewater treatment, amperometric chemical sensing, and electrochemical synthesis.

When exposed to air, many metals naturally form a hard, relatively inert surface layer, usually an oxide (termed the "native oxide layer") or a nitride, that serves as a passivation layer - i.e. these metals are "self-protecting". In the case of silver, the dark tarnish is a passivation layer of silver sulfide formed from reaction with environmental hydrogen sulfide. Aluminium similarly forms a stable protective oxide layer which is why it does not "rust". (In contrast, some base metals, notably iron, oxidize readily to form a rough, porous coating of rust that adheres loosely, is of higher volume than the original displaced metal, and sloughs off readily; all of which permit & promote further oxidation.) The passivation layer of oxide markedly slows further oxidation and corrosion in room-temperature air for aluminium, beryllium, chromium, zinc, titanium, and silicon (a metalloid). The inert surface layer formed by reaction with air has a thickness of about 1.5 nm for silicon, 1–10 nm for beryllium, and 1 nm initially for titanium, growing to 25 nm after several years. Similarly, for aluminium, it grows to about 5 nm after several years.

Having a mean density of 3,346.4 kg/m, the Moon is a differentiated body, being composed of a geochemically distinct crust, mantle, and planetary core. This structure is believed to have resulted from the fractional crystallization of a magma ocean shortly after its formation about 4.5 billion years ago. The energy required to melt the outer portion of the Moon is commonly attributed to a giant impact event that is postulated to have formed the Earth-Moon system, and the subsequent reaccretion of material in Earth orbit. Crystallization of this magma ocean would have given rise to a mafic mantle and a plagioclase-rich crust.

Geochemical mapping from orbit implies that the crust of the Moon is largely anorthositic in composition, consistent with the magma ocean hypothesis. In terms of elements, the lunar crust is composed primarily of oxygen, silicon, magnesium, iron, calcium, and aluminium, but important minor and trace elements such as titanium, uranium, thorium, potassium, sulphur, manganese, chromium, and hydrogen are present as well. Based on geophysical techniques, the crust is estimated to be on average about 50 km thick.

Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an in situ Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom (see cosmic ray spallation). These nuclides are produced within Earth materials such as rocks or soil, in Earth's atmosphere, and in extraterrestrial items such as meteoroids. By measuring cosmogenic nuclides, scientists are able to gain insight into a range of geological and astronomical processes. There are both radioactive and stable cosmogenic nuclides. Some of these radionuclides are tritium, carbon-14 and phosphorus-32.

Certain light (low atomic number) primordial nuclides (isotopes of lithium, beryllium and boron) are thought to have been created not only during the Big Bang, but also (and perhaps primarily) to have been made after the Big Bang, but before the condensation of the Solar System, by the process of cosmic ray spallation on interstellar gas and dust. This explains their higher abundance in cosmic dust as compared with their abundances on Earth. This also explains the overabundance of the early transition metals just before iron in the periodic table – the cosmic-ray spallation of iron produces scandium through chromium on the one hand and helium through boron on the other. However, the arbitrary defining qualification for cosmogenic nuclides of being formed "in situ in the Solar System" (meaning inside an already aggregated piece of the Solar System) prevents primordial nuclides formed by cosmic ray spallation before the formation of the Solar System from being termed "cosmogenic nuclides"—even though the mechanism for their formation is exactly the same. These same nuclides still arrive on Earth in small amounts in cosmic rays, and are formed in meteoroids, in the atmosphere, on Earth, "cosmogenically". However, beryllium (all of it stable beryllium-9) is present primordially in the Solar System in much larger amounts, having existed prior to the condensation of the Solar System, and thus present in the materials from which the Solar System formed.

The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula XY(Si,Al)₂O₆, where X represents ions of calcium (Ca), sodium (Na), iron (Fe(II)) or magnesium (Mg) and more rarely zinc, manganese or lithium, and Y represents ions of smaller size, such as chromium (Cr), aluminium (Al), magnesium (Mg), cobalt (Co), manganese (Mn), scandium (Sc), titanium (Ti), vanadium (V) or even iron (Fe(II) or Fe(III)). Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes. They share a common structure consisting of single chains of silica tetrahedra. Pyroxenes that crystallize in the monoclinic system are known as clinopyroxenes and those that crystallize in the orthorhombic system are known as orthopyroxenes.

The name pyroxene is derived from the Ancient Greek words for 'fire' (πυρ, pur) and 'stranger' (ξένος, xénos). Pyroxenes were so named due to their presence in volcanic lavas, where they are sometimes found as crystals embedded in volcanic glass; it was assumed they were impurities in the glass, hence the name meaning "fire stranger". However, they are simply early-forming minerals that crystallized before the lava erupted.