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Rust on a steel bridge
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Rusted bolt
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A blacksmith removing rust with sand prior to welding
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Rust damage in automobiles can create hidden dangers. QtubIronPillarJPG|thumb|right| Iron pillar at Delhi India containing 98% wrought iron]] Wrought iron is commercially pure Iron. Ductile iron, also called ductile cast iron, spheroidal graphite iron, or nodular cast iron, is a type of Cast iron invented in 1943 by blacksmith is a person who creates objects from Iron or Steel by Forging the Metal; i
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Rusting can completely degrade iron. Note the galvanization on the unrusted portions.
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Rust is a general term for a series of iron oxides, usually red oxides, formed by the reaction of iron with oxygen in the presence of water or air moisture. Altogether there are sixteen known Iron Oxides and oxyhydroxides Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Several forms of rust are distinguishable visually and by spectroscopy, and form under different circumstances. Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ [1] Rust consists of hydrated iron(III) oxides Fe2O3·nH2O, iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3. Iron(III oxide —also known as ferric oxide, Hematite, red iron oxide, synthetic maghemite, colcothar, or simply Rust —is A number of species are dubbed iron(III oxide-hydroxide. These chemicals are Oxide - Hydroxides of Iron, and may occur in Anhydrous (( or Rusting is the common term for corrosion of iron and its alloys, such as steel. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Other metals undergo equivalent corrosion, but the resulting oxides are not commonly called rust. Given sufficient time, oxygen, and water, any iron mass eventually converts entirely to rust and disintegrates. The corrosion of aluminium is extremely slow because the resulting aluminium oxide forms a conformal coating, which protects the remaining aluminium. WikipediaNaming This process is known as passivation. Passivation is the process of making a material "passive" in relation to another material prior to using the materials together
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Chemical reactions
The oxidation of iron metal
When in contact with water and oxygen iron will rust. If salt is present, for example, in salt water, and the metal rusts more quickly. This chemical reaction is used in the production of handwarmers[2] Iron metal is relatively unaffected by pure water or by dry oxygen. As with other metals, a tightly adhering oxide coating, a passivation layer, protects the bulk iron from further oxidation. Passivation is the process of making a material "passive" in relation to another material prior to using the materials together Thus, the conversion of the passivating iron oxide layer to rust results from the combined action of two agents, usually oxygen 'and' water. Other degrading solutions are sulfur dioxide in water and carbon dioxide in water. Under these corrosive conditions, iron(III) species are formed. Unlike iron(II) oxides, iron(III) oxides are not passivating because these materials do not adhere to the bulk metal. As these iron(III) compounds form and flake off from the surface, fresh iron is exposed, and the corrosion process continues until all of the iron(0) is either consumed or all of the oxygen, water, carbon dioxide, or sulfur dioxide in the system are removed or consumed. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single [3]
Chemical reactions associated with rusting
The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen. Electrochemistry is a branch of Chemistry that studies Chemical reactions which take place in a Solution at the interface of an electron conductor Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the [4] The rate of corrosion is affected by water and accelerated by electrolytes, as illustrated by the effects of road salt (calcium chloride) on the corrosion of automobiles. An electrolyte is any substance containing free Ions that behaves as an electrically conductive medium Calcium chloride (CaCl2 is an ionic compound of Calcium and Chlorine. The key reaction is the reduction of oxygen:
- O2 + 4 e- + 2 H2O → 4 OH-
Because it forms hydroxide ions, this process is strongly affected by the presence of acid. In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Indeed, the corrosion of most metals by oxygen is accelerated at low pH. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings pH is the measure of the acidity or alkalinity of a Solution. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows:
- Fe → Fe2+ + 2 e−
The following redox reaction also occurs in the presence of water and is crucial to the formation of rust:
- 2 Fe2+ + 0. 5 O2 → 2 Fe3+ + O2−
Additionally, the following multistep acid-base reactions affect the course of rust formation:
- Fe2+ + 2 H2O ⇌ Fe(OH)2 + 2 H+
- Fe3+ + 3 H2O ⇌ Fe(OH)3 + 3 H+
as do the following dehydration equilibria:
- Fe(OH)2 ⇌ FeO + H2O
- Fe(OH)3 ⇌ FeO(OH) + H2O
- 2 FeO(OH) ⇌ Fe2O3 + H2O
From the above equations, it is also seen that the corrosion products are dictated by the availability of water and oxygen. With limited dissolved oxygen, iron(II)-containing materials are favoured, including FeO and black lodestone (Fe3O4). Iron(II oxide, also known as ferrous oxide, iron oxide/oxidized iron or more commonly rusted Lodestone or loadstone refers to either Magnetite, a Magnetic Mineral form of iron(II, Iron(III oxide High oxygen concentrations favour ferric materials with the nominal formulae Fe(OH)3-xOx/2. Ferric is a term that means containing or having to do with Iron, derived from the Latin word ferrum, meaning "iron" The nature of rust changes with time, reflecting the slow rates of the reactions of solids. Furthermore, these complex processes are affected by the presence of other ions, such as Ca2+, which both serve as an electrolyte, and thus accelerate rust formation, or combine with the hydroxides and oxides of iron to precipitate a variety of Ca-Fe-O-OH species. Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element
Rust prevention
Rust is permeable to air and water, therefore the interior iron continues to corrode. Rust prevention thus requires coatings that preclude rust formation. Stainless steel forms a passivation layer of chromium(III) oxide. In Metallurgy, stainless steel is defined as a Steel Alloy with a minimum of 11 Chromium(III oxide is the Inorganic compound of the formula Cr2O3 Similar passivation behavior occurs with magnesium, copper, titanium, and zinc. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30
An important approach to rust prevention entails galvanization, which typically consists of coating zinc by either hot-dip galvanizing or electroplating. Hot-dip galvanizing is a form of Galvanization. It is the process of coating Iron or Steel with a thin Zinc layer by passing the steel Electroplating is the process of using electrical current to reduce Cations of a desired material from a solution and coat a conductive object Zinc is traditionally used because it is cheap and adheres well to steel. In more corrosive environments (such as salt water) cadmium is preferred. Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Galvanization often fails at seams, holes, and joints, where the coating is pierced. In these cases the coating provides cathodic protection to metal, where it acts as a galvanic anode rusting in preference. Cathodic protection ( CP) is a technique to control the Corrosion of a metal surface by making it work as a Cathode of an Electrochemical More modern coatings add aluminium to the coating as zinc-alume, aluminium will migrate to cover scratches and thus provide protection for longer. These approaches rely on the aluminium and zinc oxides protecting the once-scratched surface rather than oxidizing as a sacrificial anode. A sacrificial anode, or sacrificial rod, is a metallic Anode used in Cathodic protection where it is intended to be dissolved to protect other metallic
Several other methods are available to control corrosion and prevent the formation of rust, colloquially termed rustproofing:
- Cathodic protection makes the iron a cathode in a battery formed whenever water contacts the iron and also a sacrificial anode made from something with a more negative electrode potential, commonly zinc or magnesium. Rust-proofing is the name process whereby the rate at which objects made of Iron and/or Steel begin to Rust is reduced (in the long term it cannot be stopped unless Cathodic protection ( CP) is a technique to control the Corrosion of a metal surface by making it work as a Cathode of an Electrochemical In Electrochemistry, the standard electrode potential, abbreviated Eo E0 or EO (with a superscript Plimsoll character pronounced The electrode alone does not react in water but only provides electrons that are otherwise provided by the iron.
- Bluing is a technique that can provide limited resistance to rusting for small steel items, such as firearms; for it to be successful, water-displacing oil is rubbed onto the blued steel. Bluing is a Passivation process in which steel is partially protected against Rust, and is named after the blue-black appearance of the resulting protective finish
- Rust formation can be controlled with coatings, such as paint, that isolate the iron from the environment. Coating is a Covering that is applied to an object The aim of applying coatings is to improve surface properties of a bulk material usually referred to as a substrate Paint is any Liquid, liquifiable or mastic composition which after application to a substrate in a thin layer is converted to an opaque Solid Large structures with enclosed box sections, such as ships and modern automobiles, often have a wax-based product (technically a "slushing oil") injected into these sections. Such treatments also contain rust inhibitors. Covering steel with concrete provides protection to steel by the high pH environment at the steel-concrete interface.
- A simple and inexpensive way to remove rust from steel surfaces by hand is to rub the steel with aluminium foil dipped in water. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 WikipediaManual of Style#National varieties of English --> Aluminium foil (known Aluminium has a higher reduction potential than the iron in steel, which may help transfer oxygen atoms from the iron to the aluminium. Reduction potential (also known as redox potential, oxidation / reduction potential or ORP) is the tendency of a Chemical species to acquire Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The aluminium foil is softer than steel and will not scratch it, as steel wool will, but as the aluminium oxidizes, the aluminium oxide produced becomes a fine metal polishing compound. Steel wool or 'wire wool' is a bundle of strands of very fine soft Steel filaments used in finishing and repairing work to polish wood or metal objects as well as for
Economic impact
Rust is associated with degradation of iron-based tools and structures. Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings As rust has a much higher volume than the originating mass of iron, its build-up can also cause failure by forcing apart adjacent parts — a phenomenon sometimes known as "rust smacking. " It was the cause of the collapse of the Mianus river bridge in 1983, when the bearings rusted internally and pushed one corner of the road slab off its support. The Mianus River Bridge on Interstate 95 in the Cos Cob section of Greenwich Connecticut had a 100-foot (30 Three drivers on the roadway at the time died as the slab fell into the river below. The following NTSB investigation showed that a drain in the road had been blocked for road re-surfacing, and had not been unblocked so that runoff water penetrated the support hangers. The National Transportation Safety Board (NTSB is an independent U It was also difficult for maintenance engineers to see the bearings from the inspection walkway. Rust was also an important factor in the Silver Bridge disaster of 1967 in West Virginia, when a steel suspension bridge collapsed in less than a minute, killing 46 drivers and passengers on the bridge at the time. The Silver Bridge was an Eyebar Chain Suspension bridge built in 1928 and was named for the color of its Aluminum paint West Virginia ( is a state in the Appalachian Upland South, and Mid-Atlantic regions of the United States, bordered by This article is concerned with a particular type of suspension bridge the suspended-deck type
Kinzua Bridge in Pennsylvania was blown down by a tornado in 2003 largely because the central base bolts holding the structure to the ground had rusted away, leaving the bridge resting by gravity alone. The Kinzua Bridge, also known as the Kinzua Viaduct, was a railway Trestle that spanned the Kinzua Creek in McKean County in The Commonwealth of Pennsylvania ( often colloquially referred to as PA (its abbreviation by natives and Northeasterners is a state located in the Northeastern A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus
Similarly corrosion of concrete-covered steel and iron can cause the concrete to spall, creating severe structural problems. Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms including as a result of Projectile impact Corrosion It is one of the most common failure modes of reinforced concrete bridges. Reinforced concrete is Concrete in which reinforcement bars (" Rebars quot or fibers have been incorporated to strengthen a material that would otherwise be A bridge is a Structure built to span a Gorge, Valley, Road, railroad track, River, Body of water
References
- ^ Interview, David Des Marais.
- ^ ScienceIQ.com
- ^ Holleman, A. F. ; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Hubert Gräfen, Elmar-Manfred Horn, Hartmut Schlecker, Helmut Schindler "Corrosion" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH: Weinheim, 2002. DOI: 10. 1002/14356007. b01_08
See also
External links
- corrosion case studies Analysis of corrosion
- Corrosion Doctors Rusting article
Dictionary
rust
-noun
- The deteriorated state of iron or steel as a result of moisture and oxidation.
- (colour) A reddish-brown color.
- A disease of plants caused by a reddish-brown fungus.
-verb
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