Misplaced Pages

#688311

98-398: Isatis tinctoria , also called woad ( / ˈ w oʊ d / ), dyer's woad, dyer's-weed , or glastum , is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, Isatis , derives from the ancient Greek word for the plant, ἰσάτις . It is occasionally known as Asp of Jerusalem . Woad is also

196-404: A DC power source (such as a cathodic protection rectifier ). Anodes for ICCP systems are tubular and solid rod shapes of various specialized materials. These include high silicon cast iron , graphite, mixed metal oxide or platinum coated titanium or niobium coated rod and wires. Anodic protection impresses anodic current on the structure to be protected (opposite to the cathodic protection). It

294-1823: A molecular phylogeny of plants placed the flowering plants in their evolutionary context: Bryophytes [REDACTED] Lycophytes [REDACTED] Ferns [REDACTED] [REDACTED] [REDACTED] The main groups of living angiosperms are: Amborellales [REDACTED] 1 sp. New Caledonia shrub Nymphaeales [REDACTED] c. 80 spp. water lilies & allies Austrobaileyales [REDACTED] c. 100 spp. woody plants Magnoliids [REDACTED] c. 10,000 spp. 3-part flowers, 1-pore pollen, usu. branch-veined leaves Chloranthales [REDACTED] 77 spp. Woody, apetalous Monocots [REDACTED] c. 70,000 spp. 3-part flowers, 1 cotyledon , 1-pore pollen, usu. parallel-veined leaves   Ceratophyllales [REDACTED] c. 6 spp. aquatic plants Eudicots [REDACTED] c. 175,000 spp. 4- or 5-part flowers, 3-pore pollen, usu. branch-veined leaves Amborellales Melikyan, Bobrov & Zaytzeva 1999 Nymphaeales Salisbury ex von Berchtold & Presl 1820 Austrobaileyales Takhtajan ex Reveal 1992 Chloranthales Mart. 1835 Canellales Cronquist 1957 Piperales von Berchtold & Presl 1820 Magnoliales de Jussieu ex von Berchtold & Presl 1820 Laurales de Jussieu ex von Berchtold & Presl 1820 Acorales Link 1835 Alismatales Brown ex von Berchtold & Presl 1820 Petrosaviales Takhtajan 1997 Dioscoreales Brown 1835 Pandanales Brown ex von Berchtold & Presl 1820 Liliales Perleb 1826 Asparagales Link 1829 Arecales Bromhead 1840 Poales Small 1903 Zingiberales Grisebach 1854 Commelinales de Mirbel ex von Berchtold & Presl 1820 Corrosive substance In

392-454: A pit or crack, or it can extend across a wide area, more or less uniformly corroding the surface. Because corrosion is a diffusion -controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the exposed surface, such as passivation and chromate conversion , can increase a material's corrosion resistance. However, some corrosion mechanisms are less visible and less predictable. The chemistry of corrosion

490-442: A woody stem ), grasses and grass-like plants, a vast majority of broad-leaved trees , shrubs and vines , and most aquatic plants . Angiosperms are distinguished from the other major seed plant clade, the gymnosperms , by having flowers , xylem consisting of vessel elements instead of tracheids , endosperm within their seeds, and fruits that completely envelop the seeds. The ancestors of flowering plants diverged from

588-410: A barrier to further oxidation. The chemical composition and microstructure of a passive film are different from the underlying metal. Typical passive film thickness on aluminium, stainless steels, and alloys is within 10 nanometers. The passive film is different from oxide layers that are formed upon heating and are in the micrometer thickness range – the passive film recovers if removed or damaged whereas

686-408: A calcareous deposit, which will help shield the metal from further attack. Metal dusting is a catastrophic form of corrosion that occurs when susceptible materials are exposed to environments with high carbon activities, such as synthesis gas and other high-CO environments. The corrosion manifests itself as a break-up of bulk metal to metal powder. The suspected mechanism is firstly the deposition of

784-845: A dye shop with remains of both woad and madder have been excavated and dated to the 10th century. In medieval times, centres of woad cultivation lay in Lincolnshire and Somerset in England, Jülich and the Erfurt area in Thuringia in Germany, Piedmont and Tuscany in Italy, and Gascogne , Normandy , the Somme Basin (from Amiens to Saint-Quentin ), Brittany and, above all, Languedoc in France. This last region, in

882-671: A dye. There has also been some revival of the use of woad for craft purposes. The first archaeological finds of woad seeds date to the Neolithic period. The seeds have been found in the cave of l'Audoste, Bouches-du-Rhône , France. Impressions of seeds of Färberwaid (Isatis tinctoria L.) or German indigo, of the plant family Brassicaceae , have been found on pottery in the Iron Age settlement of Heuneburg , Germany. Seed and pod fragments have also been found in an Iron Age pit at Dragonby, North Lincolnshire, United Kingdom. The Hallstatt burials of

980-495: A few micrometers across, making it even less noticeable. Crevice corrosion is a localized form of corrosion occurring in confined spaces (crevices), to which the access of the working fluid from the environment is limited. Formation of a differential aeration cell leads to corrosion inside the crevices. Examples of crevices are gaps and contact areas between parts, under gaskets or seals, inside cracks and seams, spaces filled with deposits, and under sludge piles. Crevice corrosion

1078-481: A given alloy's ability to re-form a passivating film. In the worst case, almost all of the surface will remain protected, but tiny local fluctuations will degrade the oxide film in a few critical points. Corrosion at these points will be greatly amplified, and can cause corrosion pits of several types, depending upon conditions. While the corrosion pits only nucleate under fairly extreme circumstances, they can continue to grow even when conditions return to normal, since

SECTION 10

#1732858699689

1176-461: A graphite layer on the surface of the metal, usually from carbon monoxide (CO) in the vapor phase. This graphite layer is then thought to form metastable M 3 C species (where M is the metal), which migrate away from the metal surface. However, in some regimes, no M 3 C species is observed indicating a direct transfer of metal atoms into the graphite layer. Various treatments are used to slow corrosion damage to metallic objects which are exposed to

1274-474: A part or structure fails . Pitting remains among the most common and damaging forms of corrosion in passivated alloys, but it can be prevented by control of the alloy's environment. Pitting results when a small hole, or cavity, forms in the metal, usually as a result of de-passivation of a small area. This area becomes anodic, while part of the remaining metal becomes cathodic, producing a localized galvanic reaction. The deterioration of this small area penetrates

1372-449: A result of heating. This non-galvanic form of corrosion can occur when a metal is subjected to a hot atmosphere containing oxygen, sulfur (" sulfidation "), or other compounds capable of oxidizing (or assisting the oxidation of) the material concerned. For example, materials used in aerospace, power generation, and even in car engines must resist sustained periods at high temperature, during which they may be exposed to an atmosphere containing

1470-434: A seed impression on an Anglo-Saxon pot. The authors theorize that vitrum could have actually referred to copper(II) sulfate 's naturally occurring variant chalcanthite or to the mineral azurite . A later study concluded the amount was "not of sufficient magnitude to provide convincing evidence that the copper was deliberately applied as paint". Woad was an important dyeing agent in much of Europe and parts of England during

1568-568: A slower rate. When immersed separately, each metal corrodes at its own rate. What type of metal(s) to use is readily determined by following the galvanic series . For example, zinc is often used as a sacrificial anode for steel structures. Galvanic corrosion is of major interest to the marine industry and also anywhere water (containing salts) contacts pipes or metal structures. Factors such as relative size of anode , types of metal, and operating conditions ( temperature , humidity , salinity , etc.) affect galvanic corrosion. The surface area ratio of

1666-521: A smooth surface. For example, phosphoric acid may also be used to electropolish copper but it does this by removing copper, not the products of copper corrosion. Some metals are more intrinsically resistant to corrosion than others (for some examples, see galvanic series ). There are various ways of protecting metals from corrosion (oxidation) including painting, hot-dip galvanization , cathodic protection , and combinations of these. The materials most resistant to corrosion are those for which corrosion

1764-515: A tattoo pigment have claimed that it does not work well, and is actually caustic and causes scarring when put into the skin. It has also been claimed that Caesar was referring to some form of copper - or iron -based pigment. Analysis done on the Lindow Man did return evidence of copper. The same study also noted that the earliest definite reference to the woad plant in the British Isles dates to

1862-610: A total of 64 angiosperm orders and 416 families. The diversity of flowering plants is not evenly distributed. Nearly all species belong to the eudicot (75%), monocot (23%), and magnoliid (2%) clades. The remaining five clades contain a little over 250 species in total; i.e. less than 0.1% of flowering plant diversity, divided among nine families. The 25 most species-rich of 443 families, containing over 166,000 species between them in their APG circumscriptions, are: The botanical term "angiosperm", from Greek words angeíon ( ἀγγεῖον 'bottle, vessel') and spérma ( σπέρμα 'seed'),

1960-471: A uniform potential, the driving force for the corrosion reaction is halted. For galvanic CP systems, the anode material corrodes under the influence of the steel, and eventually it must be replaced. The polarization is caused by the current flow from the anode to the cathode, driven by the difference in electrode potential between the anode and the cathode. The most common sacrificial anode materials are aluminum, zinc, magnesium and related alloys. Aluminum has

2058-458: A wave of claims due to pipe failures. Most ceramic materials are almost entirely immune to corrosion. The strong chemical bonds that hold them together leave very little free chemical energy in the structure; they can be thought of as already corroded. When corrosion does occur, it is almost always a simple dissolution of the material or chemical reaction, rather than an electrochemical process. A common example of corrosion protection in ceramics

SECTION 20

#1732858699689

2156-600: A woad mill model, photos and other items used in woad production. A major market for woad was at Görlitz in Lausitz. The citizens of the five Thuringian Färberwaid (dye woad) towns of Erfurt , Gotha , Tennstedt , Arnstadt and Langensalza had their own charters. In Erfurt, the woad-traders gave the funds to found the University of Erfurt . Traditional fabric is still printed with woad in Thuringia, Saxony and Lusatia today: it

2254-605: A working perspective, sacrificial anodes systems are considered to be less precise than modern cathodic protection systems such as Impressed Current Cathodic Protection (ICCP) systems. Their ability to provide requisite protection has to be checked regularly by means of underwater inspection by divers. Furthermore, as they have a finite lifespan, sacrificial anodes need to be replaced regularly over time. For larger structures, galvanic anodes cannot economically deliver enough current to provide complete protection. Impressed current cathodic protection (ICCP) systems use anodes connected to

2352-858: Is starting to impact plants and is likely to cause many species to become extinct by 2100. Angiosperms are terrestrial vascular plants; like the gymnosperms, they have roots , stems , leaves , and seeds . They differ from other seed plants in several ways. The largest angiosperms are Eucalyptus gum trees of Australia, and Shorea faguetiana , dipterocarp rainforest trees of Southeast Asia, both of which can reach almost 100 metres (330 ft) in height. The smallest are Wolffia duckweeds which float on freshwater, each plant less than 2 millimetres (0.08 in) across. Considering their method of obtaining energy, some 99% of flowering plants are photosynthetic autotrophs , deriving their energy from sunlight and using it to create molecules such as sugars . The remainder are parasitic , whether on fungi like

2450-511: Is thermodynamically unfavorable. Any corrosion products of gold or platinum tend to decompose spontaneously into pure metal, which is why these elements can be found in metallic form on Earth and have long been valued. More common "base" metals can only be protected by more temporary means. Some metals have naturally slow reaction kinetics , even though their corrosion is thermodynamically favorable. These include such metals as zinc , magnesium , and cadmium . While corrosion of these metals

2548-407: Is a technique to control the corrosion of a metal surface by making it the cathode of an electrochemical cell . Cathodic protection systems are most commonly used to protect steel pipelines and tanks; steel pier piles , ships, and offshore oil platforms . For effective CP, the potential of the steel surface is polarized (pushed) more negative until the metal surface has a uniform potential. With

2646-451: Is appropriate for metals that exhibit passivity (e.g. stainless steel) and suitably small passive current over a wide range of potentials. It is used in aggressive environments, such as solutions of sulfuric acid. Anodic protection is an electrochemical method of corrosion protection by keeping metal in passive state The formation of an oxide layer is described by the Deal–Grove model , which

2744-501: Is calculated as where k is a constant, W is the weight loss of the metal in time t , A is the surface area of the metal exposed, and ρ is the density of the metal (in g/cm ). Other common expressions for the corrosion rate is penetration depth and change of mechanical properties. In 2002, the US Federal Highway Administration released a study titled "Corrosion Costs and Preventive Strategies in

2842-404: Is called a galvanic series and is useful in predicting and understanding corrosion. Often, it is possible to chemically remove the products of corrosion. For example, phosphoric acid in the form of naval jelly is often applied to ferrous tools or surfaces to remove rust. Corrosion removal should not be confused with electropolishing , which removes some layers of the underlying metal to make

2940-624: Is complex; it can be considered an electrochemical phenomenon. During corrosion at a particular spot on the surface of an object made of iron, oxidation takes place and that spot behaves as an anode . The electrons released at this anodic spot move through the metal to another spot on the object, and reduce oxygen at that spot in presence of H (which is believed to be available from carbonic acid ( H 2 CO 3 ) formed due to dissolution of carbon dioxide from air into water in moist air condition of atmosphere. Hydrogen ion in water may also be available due to dissolution of other acidic oxides from

3038-421: Is continuous and ongoing, it happens at an acceptably slow rate. An extreme example is graphite , which releases large amounts of energy upon oxidation , but has such slow kinetics that it is effectively immune to electrochemical corrosion under normal conditions. Passivation refers to the spontaneous formation of an ultrathin film of corrosion products, known as a passive film, on the metal's surface that act as

Isatis tinctoria - Misplaced Pages Continue

3136-558: Is described in The History of Woad and the Medieval Woad Vat (1998) ISBN   0-9534133-0-6 . Woad is biodegradable and safe in the environment. In Germany, there have been attempts to use it to protect wood against decay without applying dangerous chemicals. Production of woad is increasing in the UK for use in inks , particularly for inkjet printers , and dyes. In certain locations,

3234-399: Is influenced by the crevice type (metal-metal, metal-non-metal), crevice geometry (size, surface finish), and metallurgical and environmental factors. The susceptibility to crevice corrosion can be evaluated with ASTM standard procedures. A critical crevice corrosion temperature is commonly used to rank a material's resistance to crevice corrosion. In the chemical industry , hydrogen grooving

3332-603: Is known as Blaudruck (literally, "blue print(ing)"). In the Marche region, the cultivation of the plant was an important resource for the Duchy of Urbino in Italy. To fully understand the importance of the ford industry in the State of Urbino , it is enough to read the comprehensive Chapters of the art of wool in 1555, which dictated prescriptions regarding the cultivation and trade of woad, whether in loaves or macerated (powdered). Testifying to

3430-461: Is one of the most common causes of bridge accidents. As rust displaces a much higher volume than the originating mass of iron, its build-up can also cause failure by forcing apart adjacent components. It was the cause of the collapse of the Mianus River Bridge in 1983, when support bearings rusted internally and pushed one corner of the road slab off its support. Three drivers on the roadway at

3528-406: Is the corrosion of piping at grooves created by the interaction of a corrosive agent, corroded pipe constituents, and hydrogen gas bubbles . For example, when sulfuric acid ( H 2 SO 4 ) flows through steel pipes, the iron in the steel reacts with the acid to form a passivation coating of iron sulfate ( FeSO 4 ) and hydrogen gas ( H 2 ). The iron sulfate coating will protect

3626-501: Is used as an herbal medicinal tea in China for colds and tonsillar ailments. Used as a tea, it has a brownish appearance and (unlike most Chinese medicines) is mildly sweet in taste. The dye chemical extracted from woad is indigo , the same dye extracted from "true indigo", Indigofera tinctoria , but in a lower concentration. Following the Portuguese discovery of the sea route to India by

3724-400: Is used to predict and control oxide layer formation in diverse situations. A simple test for measuring corrosion is the weight loss method. The method involves exposing a clean weighed piece of the metal or alloy to the corrosive environment for a specified time followed by cleaning to remove corrosion products and weighing the piece to determine the loss of weight. The rate of corrosion ( R )

3822-485: The Alismatales grow in marine environments, spreading with rhizomes that grow through the mud in sheltered coastal waters. Some specialised angiosperms are able to flourish in extremely acid or alkaline habitats. The sundews , many of which live in nutrient-poor acid bogs , are carnivorous plants , able to derive nutrients such as nitrate from the bodies of trapped insects. Other flowers such as Gentiana verna ,

3920-548: The Hochdorf Chieftain's Grave and Hohmichele contained textiles dyed with woad. Melo and Rondão write that woad was known "as far back as the time of the ancient Egyptians, who used it to dye the cloth wrappings applied for the mummies." Skelton states that one of the early dyes discovered by the ancient Egyptians was "blue woad (Isatis tinctoria)." Lucas writes, "What has been assumed to have been Indian Indigo on ancient Egyptian fabrics may have been woad." Hall states that

4018-575: The Hôtel d'Assézat . One merchant, Jean de Bernuy, a Spanish Jew who had fled the Spanish Inquisition , was credit-worthy enough to be the main guarantor of the ransomed King Francis I after his capture at the Battle of Pavia by Charles V of Spain . Much of the woad produced here was used for the cloth industry in southern France, but it was also exported via Bayonne , Narbonne and Bordeaux to Flanders,

Isatis tinctoria - Misplaced Pages Continue

4116-580: The clade Angiospermae ( / ˌ æ n dʒ i ə ˈ s p ər m iː / ). The term 'angiosperm' is derived from the Greek words ἀγγεῖον / angeion ('container, vessel') and σπέρμα / sperma ('seed'), meaning that the seeds are enclosed within a fruit. The group was formerly called Magnoliophyta . Angiosperms are by far the most diverse group of land plants with 64 orders , 416 families , approximately 13,000 known genera and 300,000 known species . They include all forbs (flowering plants without

4214-416: The grain boundaries of stainless alloys. This chemical reaction robs the material of chromium in the zone near the grain boundary, making those areas much less resistant to corrosion. This creates a galvanic couple with the well-protected alloy nearby, which leads to "weld decay" (corrosion of the grain boundaries in the heat affected zones) in highly corrosive environments. This process can seriously reduce

4312-460: The orchids for part or all of their life-cycle, or on other plants , either wholly like the broomrapes, Orobanche , or partially like the witchweeds, Striga . In terms of their environment, flowering plants are cosmopolitan, occupying a wide range of habitats on land, in fresh water and in the sea. On land, they are the dominant plant group in every habitat except for frigid moss-lichen tundra and coniferous forest . The seagrasses in

4410-883: The "Big Five" extinction events in Earth's history, only the Cretaceous–Paleogene extinction event had occurred while angiosperms dominated plant life on the planet. Today, the Holocene extinction affects all kingdoms of complex life on Earth, and conservation measures are necessary to protect plants in their habitats in the wild ( in situ ), or failing that, ex situ in seed banks or artificial habitats like botanic gardens . Otherwise, around 40% of plant species may become extinct due to human actions such as habitat destruction , introduction of invasive species , unsustainable logging , land clearing and overharvesting of medicinal or ornamental plants . Further, climate change

4508-548: The Britanni used to colour their bodies blue with vitrum , a word that means primarily ' glass ' , but also the domestic name for the woad ( Isatis tinctoria ), besides the Gaulish loanword glastum (from Proto-Celtic * glastos ' green ' ). The connection seems to be that both glass and the woad are "water-like" ( Latin : vitrum is from Proto-Indo-European *wed-ro- , ' water-like ' ). In terms of usage,

4606-520: The Latin vitrum is more often used to refer to glass rather than woad. The use of the word for the woad might also be understood as "coloured like glass", applied to the plant and the dye made from it. Gillian Carr conducted experiments using indigo pigment derived from woad mixed with different binders to make body paint. The resulting paints yielded colours from "grey-blue, through intense midnight blue, to black". People with modern experiences with woad as

4704-619: The Low Countries, Italy, and above all Britain and Spain. After cropping the woad eddish could be let out for grazing sheep. The woad produced in Lincolnshire and Cambridgeshire in the 19th century was shipped out from the Port of Wisbech , Spalding and Boston , both the last to northern mills and the USA. The last portable woad mill was at Parson Drove , Cambridgeshire, Wisbech & Fenland Museum has

4802-585: The Unicorn (1495–1505), though typically it is the dark blue of the woad that has lasted best. Medieval uses of the dye were not limited to textiles. For example, the illustrator of the Lindisfarne Gospels ( c.  720 ) used a woad-based pigment for blue paint. As does the late 13th century North Italian manual on book illumination Liber colorum secundum magistrum Bernardum describe its usage. In Viking Age levels at archaeological digs at York ,

4900-584: The United States" on the direct costs associated with metallic corrosion in the US industry. In 1998, the total annual direct cost of corrosion in the US roughly $ 276 billion (or 3.2% of the US gross domestic product at the time). Broken down into five specific industries, the economic losses are $ 22.6 billion in infrastructure, $ 17.6 billion in production and manufacturing, $ 29.7 billion in transportation, $ 20.1 billion in government, and $ 47.9 billion in utilities. Rust

4998-717: The ancient Egyptians created their blue dye "by using indigotin, otherwise known as woad." A dye known as סטיס , satis in Aramaic , is mentioned in the Babylonian Talmud . Celtic blue is a shade of blue, also known as glas celtig in Welsh , or gorm ceilteach in both the Irish language and in Scottish Gaelic . Julius Caesar reported (in Commentarii de Bello Gallico ) that

SECTION 50

#1732858699689

5096-406: The anode and cathode directly affects the corrosion rates of the materials. Galvanic corrosion is often prevented by the use of sacrificial anodes . In any given environment (one standard medium is aerated, room-temperature seawater ), one metal will be either more noble or more active than others, based on how strongly its ions are bound to the surface. Two metals in electrical contact share

5194-423: The atmosphere). This spot behaves as a cathode . Galvanic corrosion occurs when two different metals have physical or electrical contact with each other and are immersed in a common electrolyte , or when the same metal is exposed to electrolyte with different concentrations. In a galvanic couple , the more active metal (the anode) corrodes at an accelerated rate and the more noble metal (the cathode) corrodes at

5292-434: The bridge at the time. Similarly, corrosion of concrete-covered steel and iron can cause the concrete to spall , creating severe structural problems. It is one of the most common failure modes of reinforced concrete bridges . Measuring instruments based on the half-cell potential can detect the potential corrosion spots before total failure of the concrete structure is reached. Until 20–30 years ago, galvanized steel pipe

5390-547: The common ancestor of all living gymnosperms before the end of the Carboniferous , over 300 million years ago. In the Cretaceous , angiosperms diversified explosively , becoming the dominant group of plants across the planet. Agriculture is almost entirely dependent on angiosperms, and a small number of flowering plant families supply nearly all plant-based food and livestock feed. Rice , maize and wheat provide half of

5488-483: The corrosion resistance substantially. Alternatively, antimicrobial-producing biofilms can be used to inhibit mild steel corrosion from sulfate-reducing bacteria . Controlled permeability formwork (CPF) is a method of preventing the corrosion of reinforcement by naturally enhancing the durability of the cover during concrete placement. CPF has been used in environments to combat the effects of carbonation , chlorides, frost , and abrasion. Cathodic protection (CP)

5586-432: The deposits of corrosion products, leading to localized corrosion. Accelerated low-water corrosion (ALWC) is a particularly aggressive form of MIC that affects steel piles in seawater near the low water tide mark. It is characterized by an orange sludge, which smells of hydrogen sulfide when treated with acid. Corrosion rates can be very high and design corrosion allowances can soon be exceeded leading to premature failure of

5684-536: The development of a chemical process to synthesize the pigment, both the woad and natural indigo industries collapsed in the first years of the 20th century. The last commercial harvest of woad until recent times occurred in 1932, in Lincolnshire , Britain. Small amounts of woad are now grown in the UK and France to supply craft dyers. The classic book about woad is The Woad Plant and its Dye by J. B. Hurry, Oxford University Press of 1930, which contains an extensive bibliography. A method for producing blue dye from woad

5782-475: The environment is controlled (especially in recirculating systems), corrosion inhibitors can often be added to it. These chemicals form an electrically insulating or chemically impermeable coating on exposed metal surfaces, to suppress electrochemical reactions. Such methods make the system less sensitive to scratches or defects in the coating, since extra inhibitors can be made available wherever metal becomes exposed. Chemicals that inhibit corrosion include some of

5880-635: The flowering plants as an unranked clade without a formal Latin name (angiosperms). A formal classification was published alongside the 2009 revision in which the flowering plants rank as the subclass Magnoliidae. From 1998, the Angiosperm Phylogeny Group (APG) has reclassified the angiosperms, with updates in the APG II system in 2003, the APG III system in 2009, and the APG IV system in 2016. In 2019,

5978-513: The form of compacted oxide layer glazes , prevent or reduce wear during high-temperature sliding contact of metallic (or metallic and ceramic) surfaces. Thermal oxidation is also commonly used to produce controlled oxide nanostructures, including nanowires and thin films. Microbial corrosion , or commonly known as microbiologically influenced corrosion (MIC), is a corrosion caused or promoted by microorganisms , usually chemoautotrophs . It can apply to both metallic and non-metallic materials, in

SECTION 60

#1732858699689

6076-411: The grain boundaries. Special alloys, either with low carbon content or with added carbon " getters " such as titanium and niobium (in types 321 and 347, respectively), can prevent this effect, but the latter require special heat treatment after welding to prevent the similar phenomenon of "knifeline attack". As its name implies, corrosion is limited to a very narrow zone adjacent to the weld, often only

6174-403: The highest capacity, and magnesium has the highest driving voltage and is thus used where resistance is higher. Zinc is general purpose and the basis for galvanizing. A number of problems are associated with sacrificial anodes. Among these, from an environmental perspective, is the release of zinc, magnesium, aluminum and heavy metals such as cadmium into the environment including seawater. From

6272-532: The importance that this crop had in the economy in addition to the archival documents was the identification of a hundred millstones surveyed by Delio Bischi in the province of Pesaro and Urbino, the original use of which had become completely unknown as their memory had been lost. The woad plant's roots are used in Traditional Chinese medicine to make a medicine known as banlangen ( bǎnlán'gēn 板蓝根 ) that purports to have antiviral properties. Banlangen

6370-419: The interface with the metal that leads to the buildup of an electronic barrier opposing electron flow and an electronic depletion region that prevents further oxidation reactions. These results indicate a mechanism of "electronic passivation". The electronic properties of this semiconducting oxide film also provide a mechanistic explanation of corrosion mediated by chloride , which creates surface states at

6468-560: The interior and causing extensive damage even while the outer protective layer remains apparently intact for a period of time. Plating , painting , and the application of enamel are the most common anti-corrosion treatments. They work by providing a barrier of corrosion-resistant material between the damaging environment and the structural material. Aside from cosmetic and manufacturing issues, there may be tradeoffs in mechanical flexibility versus resistance to abrasion and high temperature. Platings usually fail only in small sections, but if

6566-500: The interior of a pit is naturally deprived of oxygen and locally the pH decreases to very low values and the corrosion rate increases due to an autocatalytic process. In extreme cases, the sharp tips of extremely long and narrow corrosion pits can cause stress concentration to the point that otherwise tough alloys can shatter; a thin film pierced by an invisibly small hole can hide a thumb sized pit from view. These problems are especially dangerous because they are difficult to detect before

6664-418: The long-lasting performance of this group of materials. If breakdown occurs in the passive film due to chemical or mechanical factors, the resulting major modes of corrosion may include pitting corrosion , crevice corrosion , and stress corrosion cracking . Certain conditions, such as low concentrations of oxygen or high concentrations of species such as chloride which compete as anions , can interfere with

6762-518: The manner of vines or lianas . The number of species of flowering plants is estimated to be in the range of 250,000 to 400,000. This compares to around 12,000 species of moss and 11,000 species of pteridophytes . The APG system seeks to determine the number of families , mostly by molecular phylogenetics . In the 2009 APG III there were 415 families. The 2016 APG IV added five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales and Vahliales), along with some new families, for

6860-433: The mechanical strength of welded joints over time. A stainless steel is said to be "sensitized" if chromium carbides are formed in the microstructure. A typical microstructure of a normalized type 304 stainless steel shows no signs of sensitization, while a heavily sensitized steel shows the presence of grain boundary precipitates. The dark lines in the sensitized microstructure are networks of chromium carbides formed along

6958-574: The medieval period. However, dye traders began to import indigo during the sixteenth and seventeenth centuries, which threatened to replace locally grown woad as the primary blue dye. The translation of vitrum as woad may date to this period. Woad was one of the three staples of the European dyeing industry, along with weld (yellow) and madder (red). Chaucer mentions their use by the dyer ("litestere") in his poem The Former Age : The three colours can be seen together in tapestries such as The Hunt of

7056-474: The metal and can lead to failure. This form of corrosion is often difficult to detect due to the fact that it is usually relatively small and may be covered and hidden by corrosion-produced compounds. Stainless steel can pose special corrosion challenges, since its passivating behavior relies on the presence of a major alloying component ( chromium , at least 11.5%). Because of the elevated temperatures of welding and heat treatment, chromium carbides can form in

7154-484: The metal coating thickness. Painting either by roller or brush is more desirable for tight spaces; spray would be better for larger coating areas such as steel decks and waterfront applications. Flexible polyurethane coatings, like Durabak-M26 for example, can provide an anti-corrosive seal with a highly durable slip resistant membrane. Painted coatings are relatively easy to apply and have fast drying times although temperature and humidity may cause dry times to vary. If

7252-439: The metal's oxide film. These pores allow the oxide to grow much thicker than passivating conditions would allow. At the end of the treatment, the pores are allowed to seal, forming a harder-than-usual surface layer. If this coating is scratched, normal passivation processes take over to protect the damaged area. Anodizing is very resilient to weathering and corrosion, so it is commonly used for building facades and other areas where

7350-504: The most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen , hydrogen, or hydroxide. Rusting , the formation of red-orange iron oxides, is a well-known example of electrochemical corrosion. This type of corrosion typically produces oxides or salts of the original metal and results in a distinctive coloration. Corrosion can also occur in materials other than metals, such as ceramics or polymers , although in this context,

7448-714: The name of a blue dye produced from the leaves of the plant. Woad is native to the steppe and desert zones of the Caucasus , Central Asia to Eastern Siberia and Western Asia but is now also found in South-Eastern and Central Europe and western North America . Since ancient times, woad was an important source of blue dye and was cultivated throughout Europe, especially in Western and Southern Europe. In medieval times, there were important woad-growing regions in England, Germany and France. Towns such as Toulouse became prosperous from

7546-437: The navigator Vasco da Gama in 1498, great amounts of indigo were imported from Asia. Laws were passed in some parts of Europe to protect the woad industry from the competition of the indigo trade. It was proclaimed that indigo caused yarns to rot. This prohibition was repeated in 1594 and again in 1603. In France, Henry IV , in an edict of 1609, forbade under pain of death the use of "the false and pernicious Indian drug". With

7644-465: The oxide layer does not. Passivation in natural environments such as air, water and soil at moderate pH is seen in such materials as aluminium , stainless steel , titanium , and silicon . Passivation is primarily determined by metallurgical and environmental factors. The effect of pH is summarized using Pourbaix diagrams , but many other factors are influential. Some conditions that inhibit passivation include high pH for aluminium and zinc, low pH or

7742-407: The oxide surface that lead to electronic breakthrough, restoration of anodic currents, and disruption of the electronic passivation mechanism. Passivation is extremely useful in mitigating corrosion damage, however even a high-quality alloy will corrode if its ability to form a passivating film is hindered. Proper selection of the right grade of material for the specific environment is important for

7840-519: The plant is classified as a non-native and invasive weed. It is listed as a noxious weed by the agriculture departments of several states in the western United States: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. In Montana, it has been the target of an extensive, and largely successful, eradication attempt. Flowering plant Basal angiosperms Core angiosperms Flowering plants are plants that bear flowers and fruits , and form

7938-413: The plating is more noble than the substrate (for example, chromium on steel), a galvanic couple will cause any exposed area to corrode much more rapidly than an unplated surface would. For this reason, it is often wise to plate with active metal such as zinc or cadmium . If the zinc coating is not thick enough the surface soon becomes unsightly with rusting obvious. The design life is directly related to

8036-450: The potentially highly-corrosive products of combustion. Some products of high-temperature corrosion can potentially be turned to the advantage of the engineer. The formation of oxides on stainless steels, for example, can provide a protective layer preventing further atmospheric attack, allowing for a material to be used for sustained periods at both room and high temperatures in hostile conditions. Such high-temperature corrosion products, in

8134-630: The presence of chloride ions for stainless steel, high temperature for titanium (in which case the oxide dissolves into the metal, rather than the electrolyte) and fluoride ions for silicon. On the other hand, unusual conditions may result in passivation of materials that are normally unprotected, as the alkaline environment of concrete does for steel rebar . Exposure to a liquid metal such as mercury or hot solder can often circumvent passivation mechanisms. It has been shown using electrochemical scanning tunneling microscopy that during iron passivation, an n-type semiconductor Fe(III) oxide grows at

8232-415: The presence or absence of oxygen. Sulfate-reducing bacteria are active in the absence of oxygen (anaerobic); they produce hydrogen sulfide , causing sulfide stress cracking . In the presence of oxygen (aerobic), some bacteria may directly oxidize iron to iron oxides and hydroxides, other bacteria oxidize sulfur and produce sulfuric acid causing biogenic sulfide corrosion . Concentration cells can form in

8330-473: The salts in hard water (Roman water systems are known for their mineral deposits ), chromates , phosphates , polyaniline , other conducting polymers , and a wide range of specially designed chemicals that resemble surfactants (i.e., long-chain organic molecules with ionic end groups). Aluminium alloys often undergo a surface treatment. Electrochemical conditions in the bath are carefully adjusted so that uniform pores, several nanometers wide, appear in

8428-407: The same electrons, so that the "tug-of-war" at each surface is analogous to competition for free electrons between the two materials. Using the electrolyte as a host for the flow of ions in the same direction, the noble metal will take electrons from the active one. The resulting mass flow or electric current can be measured to establish a hierarchy of materials in the medium of interest. This hierarchy

8526-568: The spring gentian, are adapted to the alkaline conditions found on calcium -rich chalk and limestone , which give rise to often dry topographies such as limestone pavement . As for their growth habit , the flowering plants range from small, soft herbaceous plants , often living as annuals or biennials that set seed and die after one growing season, to large perennial woody trees that may live for many centuries and grow to many metres in height. Some species grow tall without being self-supporting like trees by climbing on other plants in

8624-401: The steel from further reaction; however, if hydrogen bubbles contact this coating, it will be removed. Thus, a groove can be formed by a travelling bubble, exposing more steel to the acid, causing a vicious cycle . The grooving is exacerbated by the tendency of subsequent bubbles to follow the same path. High-temperature corrosion is chemical deterioration of a material (typically a metal) as

8722-466: The steel pile. Piles that have been coated and have cathodic protection installed at the time of construction are not susceptible to ALWC. For unprotected piles, sacrificial anodes can be installed locally to the affected areas to inhibit the corrosion or a complete retrofitted sacrificial anode system can be installed. Affected areas can also be treated using cathodic protection, using either sacrificial anodes or applying current to an inert anode to produce

8820-475: The surface will come into regular contact with the elements. While being resilient, it must be cleaned frequently. If left without cleaning, panel edge staining will naturally occur. Anodization is the process of converting an anode into cathode by bringing a more active anode in contact with it. A new form of protection has been developed by applying certain species of bacterial films to the surface of metals in highly corrosive environments. This process increases

8918-494: The term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including mechanical strength, appearance, and permeability to liquids and gases. Corrosive is distinguished from caustic: the former implies mechanical degradation, the latter chemical. Many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances. Corrosion can be concentrated locally to form

9016-555: 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; as a result, runoff water penetrated the support hangers. Rust was also an important factor in the Silver Bridge disaster of 1967 in West Virginia , when a steel suspension bridge collapsed within a minute, killing 46 drivers and passengers who were on

9114-521: The triangle created by Toulouse , Albi and Carcassonne , known as the Lauragais , was for a long time the biggest producer of woad, or pastel , as it was locally known. One writer commented that "woad […] hath made that country the happiest and richest in Europe." The prosperous woad merchants of Toulouse displayed their affluence in splendid mansions, many of which still stand, as the Hôtel de Bernuy and

9212-527: The weather, salt water, acids, or other hostile environments. Some unprotected metallic alloys are extremely vulnerable to corrosion, such as those used in neodymium magnets , which can spall or crumble into powder even in dry, temperature-stable indoor environments unless properly treated. When surface treatments are used to reduce corrosion, great care must be taken to ensure complete coverage, without gaps, cracks, or pinhole defects. Small defects can act as an " Achilles' heel ", allowing corrosion to penetrate

9310-399: The woad trade. Woad was eventually replaced by the more colourfast Indigofera tinctoria and, in the early 20th century, both woad and Indigofera tinctoria were replaced by synthetic blue dyes. Woad has been used medicinally for centuries. The double use of woad is seen in its name: the term Isatis is linked to its ancient use to treat wounds; the term tinctoria references its use as

9408-554: The world's staple calorie intake, and all three plants are cereals from the Poaceae family (colloquially known as grasses). Other families provide important industrial plant products such as wood , paper and cotton , and supply numerous ingredients for beverages , sugar production , traditional medicine and modern pharmaceuticals . Flowering plants are also commonly grown for decorative purposes , with certain flowers playing significant cultural roles in many societies. Out of

9506-483: Was coined in the form "Angiospermae" by Paul Hermann in 1690, including only flowering plants whose seeds were enclosed in capsules. The term angiosperm fundamentally changed in meaning in 1827 with Robert Brown , when angiosperm came to mean a seed plant with enclosed ovules. In 1851, with Wilhelm Hofmeister 's work on embryo-sacs, Angiosperm came to have its modern meaning of all the flowering plants including Dicotyledons and Monocotyledons. The APG system treats

9604-426: Was used extensively in the potable water systems for single and multi-family residents as well as commercial and public construction. Today, these systems have long ago consumed the protective zinc and are corroding internally, resulting in poor water quality and pipe failures. The economic impact on homeowners, condo dwellers, and the public infrastructure is estimated at $ 22 billion as the insurance industry braces for

#688311