1.
Cork (material)
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Cork is an impermeable buoyant material, the phellem layer of bark tissue that is harvested for commercial use primarily from Quercus suber, which is endemic to southwest Europe and northwest Africa. The montado landscape of Portugal produces approximately half of cork harvested annually worldwide, Cork was examined microscopically by Robert Hooke, which led to his discovery and naming of the cell. There are about 2,200,000 hectares of cork forest worldwide, 34% in Portugal and 27% in Spain. Annual production is about 200,000 tons,49. 6% from Portugal,30. 5% from Spain,5. 8% from Morocco,4. 9% from Algeria,3. 5% from Tunisia,3. 1% Italy, and 2. 6% from France. Once the trees are about 25 years old the cork is traditionally stripped from the trunks every nine years, the trees live for about 300 years. The cork industry is regarded as environmentally friendly. Cork production is considered sustainable because the cork tree is not cut down to obtain cork. The tree continues to live and grow, the sustainability of production and the easy recycling of cork products and by-products are two of its most distinctive aspects. Cork Oak forests also prevent desertification and are a habitat in the Iberian Peninsula. The Corticeira Amorim’s study, in particular, was developed by PricewaterhouseCoopers, results concluded that, concerning the emission of greenhouse gases, each plastic stopper released 10 times more CO2, whilst an aluminium stopper releases 26 times more CO2 than does a cork stopper. The Cork Oak is unrelated to the trees, which have corky bark but are not used for cork production. Cork is extracted only from early May to late August, when the cork can be separated from the tree without causing permanent damage, when the tree reaches 25–30 years of age and about 24 in in circumference, the cork can be removed for the first time. However, this first harvest almost always produces poor quality or male cork, bark from initial harvests can be used to make flooring, shoes, insulation and other industrial products. Subsequent extractions usually occur at intervals of 9 years, though it can take up to 13 for the cork to reach an acceptable size. If the product is of quality it is known as gentle cork. The workers who specialize in removing the cork are known as extractors and this is the most delicate phase of the work because, even though cutting the cork requires quite a bit of strength, the extractor must not damage the underlying phellogen or the tree will be harmed. To free the cork from the tree, the extractor pushes the handle of the axe into the rulers, a good extractor needs to use a firm but precise touch in order to free a large amount of cork without damaging the product or tree. These freed portions of the cork are called planks, the planks are usually carried off by hand since cork forests are rarely accessible to vehicles
2.
Steel
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Steel is an alloy of iron and other elements, primarily carbon, that is widely used in construction and other applications because of its high tensile strength and low cost. Steels base metal is iron, which is able to take on two forms, body centered cubic and face centered cubic, depending on its temperature. It is the interaction of those allotropes with the elements, primarily carbon. In the body-centred cubic arrangement, there is an atom in the centre of each cube. Carbon, other elements, and inclusions within iron act as hardening agents that prevent the movement of dislocations that otherwise occur in the lattices of iron atoms. The carbon in steel alloys may contribute up to 2. 1% of its weight. Steels strength compared to pure iron is possible at the expense of irons ductility. With the invention of the Bessemer process in the mid-19th century and this was followed by Siemens-Martin process and then Gilchrist-Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron, further refinements in the process, such as basic oxygen steelmaking, largely replaced earlier methods by further lowering the cost of production and increasing the quality of the product. Today, steel is one of the most common materials in the world and it is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations, the noun steel originates from the Proto-Germanic adjective stakhlijan, which is related to stakhla. The carbon content of steel is between 0. 002% and 2. 1% by weight for plain iron–carbon alloys and these values vary depending on alloying elements such as manganese, chromium, nickel, iron, tungsten, carbon and so on. Basically, steel is an alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction, too little carbon content leaves iron quite soft, ductile, and weak. Carbon contents higher than those of steel make an alloy, commonly called pig iron, while iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel. Common alloying elements include, manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Additional elements are important in steel, phosphorus, sulfur, silicon, and traces of oxygen, nitrogen, and copper. Alloys with a higher than 2. 1% carbon content, depending on other element content, cast iron is not malleable even when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties
3.
Copper
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Copper is a chemical element with symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with high thermal and electrical conductivity. A freshly exposed surface of copper has a reddish-orange color. Copper is one of the few metals that occur in nature in directly usable metallic form as opposed to needing extraction from an ore and this led to very early human use, from c.8000 BC. Copper used in buildings, usually for roofing, oxidizes to form a green verdigris, Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as agents, fungicides, and wood preservatives. Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the hemoglobin in fish. In humans, copper is found mainly in the liver, muscle, the adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight. The filled d-shells in these elements contribute little to interatomic interactions, unlike metals with incomplete d-shells, metallic bonds in copper are lacking a covalent character and are relatively weak. This observation explains the low hardness and high ductility of single crystals of copper, at the macroscopic scale, introduction of extended defects to the crystal lattice, such as grain boundaries, hinders flow of the material under applied stress, thereby increasing its hardness. For this reason, copper is supplied in a fine-grained polycrystalline form. The softness of copper partly explains its high conductivity and high thermal conductivity. The maximum permissible current density of copper in open air is approximately 3. 1×106 A/m2 of cross-sectional area, Copper is one of a few metallic elements with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air, as with other metals, if copper is put in contact with another metal, galvanic corrosion will occur. A green layer of verdigris can often be seen on old structures, such as the roofing of many older buildings. Copper tarnishes when exposed to sulfur compounds, with which it reacts to form various copper sulfides. There are 29 isotopes of copper, 63Cu and 65Cu are stable, with 63Cu comprising approximately 69% of naturally occurring copper, both have a spin of 3⁄2
4.
Brass
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Brass is a metal alloy made of copper and zinc, the proportions of zinc and copper can be varied to create a range of brasses with varying properties. It is an alloy, atoms of the two constituents may replace each other within the same crystal structure. By comparison, bronze is principally an alloy of copper and tin, however, bronze and brass may also include small proportions of a range of other elements including arsenic, phosphorus, aluminium, manganese, and silicon. The term is applied to a variety of brasses. Modern practice in museums and archaeology increasingly avoids both terms for objects in favour of the all-embracing copper alloy. It is also used in zippers, Brass is often used in situations in which it is important that sparks not be struck, such as in fittings and tools used near flammable or explosive materials. Brass has higher malleability than bronze or zinc, the relatively low melting point of brass and its flow characteristics make it a relatively easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard, the density of brass is 8.4 to 8.73 grams per cubic centimetre. Today, almost 90% of all alloys are recycled. Because brass is not ferromagnetic, it can be separated from ferrous scrap by passing the scrap near a powerful magnet, Brass scrap is collected and transported to the foundry where it is melted and recast into billets. Billets are heated and extruded into the form and size. The general softness of brass means that it can often be machined without the use of cutting fluid, aluminium makes brass stronger and more corrosion-resistant. Aluminium also causes a highly beneficial hard layer of oxide to be formed on the surface that is thin, transparent. Tin has an effect and finds its use especially in seawater applications. Combinations of iron, aluminium, silicon and manganese make brass wear and tear resistant, to enhance the machinability of brass, lead is often added in concentrations of around 2%. Since lead has a melting point than the other constituents of the brass. The pattern the globules form on the surface of the brass increases the available surface area which in turn affects the degree of leaching. In addition, cutting operations can smear the lead globules over the surface and these effects can lead to significant lead leaching from brasses of comparatively low lead content
5.
Plastic
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Plastic is a material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and can be molded into solid objects. Plastics are typically organic polymers of high mass, but they often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, due to their relatively low cost, ease of manufacture, versatility, and imperviousness to water, plastics are used in an enormous and expanding range of products, from paper clips to spaceships. They have already displaced many traditional materials, such as wood, stone, horn and bone, leather, paper, metal, glass, and ceramic, in most of their former uses. In developed countries, about a third of plastic is used in packaging, other uses include automobiles, furniture, and toys. In the developing world, the ratios may be different - for example, the worlds first fully synthetic plastic was bakelite, invented in New York in 1907 by Leo Baekeland who coined the term plastics. Toward the end of the century, one approach to this problem was met with wide efforts toward recycling, the word plastic is derived from the Greek πλαστικός meaning capable of being shaped or molded, from πλαστός meaning molded. The common word plastic should not be confused with the technical adjective plastic, used for insulating parts in electrical fixtures, paper laminated products, thermally insulation foams. Problems include the probability of moldings naturally being dark colors, One of the most expensive commercial polymers. It forms the basis of artistic and commercial acrylic paints when suspended in water with the use of other agents, polytetrafluoroethylene – Heat-resistant, low-friction coatings, used in things like non-stick surfaces for frying pans, plumbers tape and water slides. It is more known as Teflon. Urea-formaldehyde – One of the aminoplasts and used as an alternative to phenolics. Used as an adhesive and electrical switch housings. Early plastics were bio-derived materials such as egg and blood proteins, in 1600 BC, Mesoamericans used natural rubber for balls, bands, and figurines. Treated cattle horns were used as windows for lanterns in the Middle Ages, materials that mimicked the properties of horns were developed by treating milk-proteins with lye. In the 1800s, as industrial chemistry developed during the Industrial Revolution, the development of plastics also accelerated with Charles Goodyears discovery of vulcanization to thermoset materials derived from natural rubber. Parkesine is considered the first man-made plastic, the plastic material was patented by Alexander Parkes, In Birmingham, UK in 1856. It was unveiled at the 1862 Great International Exhibition in London, parkesine won a bronze medal at the 1862 Worlds fair in London
6.
Wire
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A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads or electricity and telecommunications signals, Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Wire gauges come in standard sizes, as expressed in terms of a gauge number. The term wire is used more loosely to refer to a bundle of such strands, as in multistranded wire. Wire comes in solid core, stranded, or braided forms, edge-wound coil springs, such as the Slinky toy, are made of special flattened wire. In some cases, strips cut from metal sheet were made into wire by pulling them through perforations in stone beads and this causes the strips to fold round on themselves to form thin tubes. This strip drawing technique was in use in Egypt by the 2nd Dynasty, from the middle of the 2nd millennium BCE most of the gold wires in jewellery are characterised by seam lines that follow a spiral path along the wire. Such twisted strips can be converted into solid round wires by rolling them between flat surfaces or the wire drawing method. The strip twist wire manufacturing method was superseded by drawing in the ancient Old World sometime between about the 8th and 10th centuries AD, there is some evidence for the use of drawing further East prior to this period. Square and hexagonal wires were made using a swaging technique. In this method a metal rod was struck between grooved metal blocks, or between a punch and a grooved metal anvil. Swaging is of great antiquity, possibly dating to the beginning of the 2nd millennium BCE in Egypt and in the Bronze and Iron Ages in Europe for torcs, twisted square-section wires are a very common filigree decoration in early Etruscan jewelry. In about the middle of the 2nd millennium BCE, a new category of decorative tube was introduced which imitated a line of granules. True beaded wire, produced by mechanically distorting a round-section wire, appeared in the Eastern Mediterranean and Italy in the seventh century BCE, a forerunner to beaded wire may be the notched strips and wires which first occur from around 2000 BCE in Anatolia. Wire was drawn in England from the medieval period, the wire was used to make wool cards and pins, manufactured goods whose import was prohibited by Edward IV in 1463. The first wire mill in Great Britain was established at Tintern in about 1568 by the founders of the Company of Mineral and Battery Works, apart from their second wire mill at nearby Whitebrook, there were no other wire mills before the second half of the 17th century. Despite the existence of mills, the drawing of wire down to fine sizes continued to be done manually. Wire is usually drawn of cylindrical form, but it may be made of any desired section by varying the outline of the holes in the draw-plate through which it is passed in the process of manufacture
7.
Nail (fastener)
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In woodworking and construction, a nail is a pin-shaped object of metal which is used as a fastener, as a peg to hang something, or sometimes as a decoration. Generally nails have a point on one end and a flattened head on the other. Nails are made in a variety of forms for specialized purposes. The most common is a wire nail, other types of nails include pins, tacks, brads, and cleats. Nails are typically driven into the workpiece by a hammer, a nail gun. A nail holds materials together by friction in the axial direction, the point of the nail is also sometimes bent over or clinched after driving to prevent pulling out. The history of the nail is divided roughly into three periods, Hand-wrought nail Cut nail Wire nail To make a wrought-iron nail, iron ore is heated with carbon. To make a nail, a blacksmith heats the rod in a forge, next, the smith cuts off the taper, and inserts it into a nail heading tool with a square hole. The top of the taper is hammered downward to form a head, Nails date back at least to Ancient Egypt — bronze nails found in Egypt have been dated 3400 BC. The Romans made extensive use of nails, the Roman army, for example, left behind seven tons of nails when it evacuated the fortress of Inchtuthil in Perthshire in the United Kingdom in 86 or 87 CE. The term penny, as it refers to nails, probably originated in medieval England to describe the price of a hundred nails, Nails themselves were sufficiently valuable and standardized to be used as an informal medium of exchange. Until around 1800 artisans known as nailers or nailors made nails by hand – note the surname Naylor, at the time of the American Revolution, England was the largest manufacturer of nails in the world. Nails were expensive and difficult to obtain in the American colonies, families often had small nail-manufacturing setups in their homes, during bad weather and at night, the entire family might work at making nails for their own use and for barter. Thomas Jefferson wrote in a letter, In our private pursuits it is an advantage that every honest employment is deemed honorable. I am myself a nail maker, the production of wrought-iron nails continued well into the 19th century, but ultimately was reduced to nails for purposes for which the softer cut nails were unsuitable, including horseshoe nails. Originally, nails were handmade, and the process was slow, nails were relatively few. This naturally produced a desire to create machines to speed up and these nails were known as cut nails or square nails because of their roughly rectangular cross section. Cut nails were one of the important factors in the increase in balloon framing beginning in the 1830s, though still used for historical renovations, and for heavy-duty applications, such as attaching boards to masonry walls, cut nails are much less common today than wire nails
8.
Hinge
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A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about an axis of rotation. Hinges may be made of material or of moving components. In biology, many joints function as hinges like the elbow joint, there are many types of door hinges. The main types include, Spring hinge which is a hinge made to provide assistance in the closing or the opening of the hinge leaves. A spring is a component of a hinge, that force to secure a hinge closed or keep a hinge opened. Barrel hinge which is a sectional barrel secured by a pivot, pivot hinges which pivot in openings in the floor and the top of the door frame. Also referred to as a double-acting floor hinge and this type is found in ancient dry stone buildings and rarely in old wooden buildings. These are also called haar-hung doors and they are a low cost alternative for use light weight doors. Butt/Mortise hinges usually in threes or fours, which are inset into the door, most residential hinges found in the U. S. are made of steel, although mortise hinges for exterior doors are often made of brass or stainless steel to prevent corrosion. Case hinges Case hinges are similar to a butt hinge however usually more of a nature most commonly used in suitcases, briefcases. Continuous hinges, or piano hinges This type of hinge is also known as a piano hinge and it runs the entire length of the door, panel, or box. Continuous hinges are manufactured with or without holes and these hinges also come in various thicknesses, pin diameters, and knuckle lengths. Concealed hinges Used for furniture doors and they are made of two parts, One part is the hinge cup and the arm, the other part is the mounting plate. Also called cup hinge, or Euro hinge, as they were developed in Europe, most such concealed hinges offer the advantage of full in situ adjustability for standoff distance from the cabinet face as well as pitch and roll by means of two screws on each hinge. Butterfly hinges, or Parliament Hinges These were known as dovetail hinges from the 17th century onwards and can be found on old desks and cabinets from about 1670 until the 18th century. The form of these hinges varied slightly between manufacturers, and their size ranged from the large for heavy doors to the tiniest decorative hinge for use on jewellery boxes. Many hinges of this type were exported to America to support the home trades limited supply and they are still found to be both fairly cheap and decorative, especially on small items
9.
Sewing needle
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A sewing needle for hand-sewing is a long slender tool with a pointed tip at one end and a hole or eye at the other. The earliest needles were made of bone or wood, modern ones are manufactured from carbon steel wire and are nickel- or 18K gold-plated for corrosion resistance. The highest quality embroidery needles are plated with platinum and one-third titanium alloy. Traditionally, needles have been kept in books or needlecases which have become objects of adornment. Sewing needles may also be kept in an etui, a box that held needles and other items such as scissors, pencils. Hand sewing needles come in a variety of types/ classes designed according to their intended use, sharp Needles, used for general hand sewing, built with a sharp point, a round eye, and are of medium length. Those with a double-eyes are able to carry two strands of thread while minimizing fabric friction, appliqué, These are considered another all-purpose needle for sewing, appliqué, and patch work. Embroidery, Also known as needles, identical to sharps but have a longer eye to enable easier threading of multiple embroidery threads. Milliners, A class of needles generally longer than sharps, useful for basting and pleating, normally used in millinery work. Beading, These needles are very fine, with an eye to enable them to fit through the centre of beads and sequins along with a long shaft to thread. Bodkin, Also called ballpoints, this is a long, thick needle with a ballpoint end and they can be flat or round and are generally used for threading elastic, ribbon or tape through casings and lace openings. Chenille, These are similar to tapestry needles but with large, long eyes, darning, Sometimes called finishing needles, these are designed with a blunt tip and large eye making them similar to tapestry needles but longer, yarn darners are the heaviest sub-variety. Doll, Not designed for hand sewing at all, these needles are made long and thin and are used for soft sculpturing on dolls, particularly facial details. Leather, Also known as glovers and as wedge needles, these have a point designed to pierce leather without tearing it, often used on leather-like materials such as vinyl. Sailmaker, Similar to leather needles, but the triangular point extends further up the shaft, tatting, These are built long with an even thickness for their entire length, including at the eye, to enable thread to be pulled through the double stitches used in tatting. Straight sizes, 3-12 long, curved,1. 5-6 long, needle size is denoted by one or more numbers on the manufacturers packet. The general convention for sizing of needles, like that of wire gauges, is that any given class of needle the length. For example, a size 9 needle will be thicker and longer than a size 12 needle, however, the needle sizes are not standardized and so a size 10 of one class may be either thinner or finer than a size 12 of another type
10.
Sumer
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Living along the valleys of the Tigris and Euphrates, Sumerian farmers were able to grow an abundance of grain and other crops, the surplus of which enabled them to settle in one place. Proto-writing in the dates back to c.3000 BC. The earliest texts come from the cities of Uruk and Jemdet Nasr and date back to 3300 BC, modern historians have suggested that Sumer was first permanently settled between c.5500 and 4000 BC by a West Asian people who spoke the Sumerian language, an agglutinative language isolate. These conjectured, prehistoric people are now called proto-Euphrateans or Ubaidians, some scholars contest the idea of a Proto-Euphratean language or one substrate language. Reliable historical records begin much later, there are none in Sumer of any kind that have dated before Enmebaragesi. Juris Zarins believes the Sumerians lived along the coast of Eastern Arabia, todays Persian Gulf region, Sumerian civilization took form in the Uruk period, continuing into the Jemdet Nasr and Early Dynastic periods. During the 3rd millennium BC, a cultural symbiosis developed between the Sumerians, who spoke a language isolate, and Akkadian-speakers, which included widespread bilingualism. The influence of Sumerian on Akkadian is evident in all areas, from lexical borrowing on a scale, to syntactic, morphological. This has prompted scholars to refer to Sumerian and Akkadian in the 3rd millennium BC as a Sprachbund, Sumer was conquered by the Semitic-speaking kings of the Akkadian Empire around 2270 BC, but Sumerian continued as a sacred language. Native Sumerian rule re-emerged for about a century in the Neo-Sumerian Empire or Third Dynasty of Ur approximately 2100-2000 BC, the term Sumerian is the common name given to the ancient non-Semitic-speaking inhabitants of Mesopotamia, Sumer, by the East Semitic-speaking Akkadians. The Sumerians referred to themselves as ùĝ saĝ gíg ga, phonetically /uŋ saŋ gi ga/, literally meaning the black-headed people, the Akkadian word Shumer may represent the geographical name in dialect, but the phonological development leading to the Akkadian term šumerû is uncertain. Hebrew Shinar, Egyptian Sngr, and Hittite Šanhar, all referring to southern Mesopotamia, in the late 4th millennium BC, Sumer was divided into many independent city-states, which were divided by canals and boundary stones. Each was centered on a dedicated to the particular patron god or goddess of the city. The Sumerian city-states rose to power during the prehistoric Ubaid and Uruk periods, classical Sumer ends with the rise of the Akkadian Empire in the 23rd century BC. Following the Gutian period, there is a brief Sumerian Renaissance in the 21st century BC, the Amorite dynasty of Isin persisted until c.1700 BC, when Mesopotamia was united under Babylonian rule. The Sumerians were eventually absorbed into the Akkadian population, 2500–2334 BC Akkadian Empire period, c. 2218–2047 BC Ur III period, c, 2047–1940 BC The Ubaid period is marked by a distinctive style of fine quality painted pottery which spread throughout Mesopotamia and the Persian Gulf. It appears that this culture was derived from the Samarran culture from northern Mesopotamia and it is not known whether or not these were the actual Sumerians who are identified with the later Uruk culture
11.
Rust
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Rust is an iron oxide, usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Several forms of rust are distinguishable both visually and by spectroscopy, and form under different circumstances, Rust consists of hydrated iron oxides Fe2O3·nH2O and iron oxide-hydroxide. Given sufficient time, oxygen, and water, any iron mass will eventually convert entirely to rust, surface rust is flaky and friable, and it provides no protection to the underlying iron, unlike the formation of patina on copper surfaces. Rusting is the term for corrosion of iron and its alloys. Many other metals undergo similar corrosion, but the resulting oxides are not commonly called rust, other forms of rust exist, like the result of reactions between iron and chloride in an environment deprived of oxygen. Rebar used in concrete pillars, which generates green rust, is an example. Rust is another name for iron oxide, which occurs when iron or an alloy that contains iron, like steel, is exposed to oxygen and moisture for a long period of time. Over time, the oxygen combines with the metal at a level, forming a new compound called an oxide. Although some people refer to rust generally as oxidation, that term is more general, although rust forms when iron undergoes oxidation. Only iron or alloys that contain iron can rust, but other metals can corrode in similar ways, the main catalyst for the rusting process is water. Iron or steel structures might appear to be solid, but water molecules can penetrate the microscopic pits, the hydrogen atoms present in water molecules can combine with other elements to form acids, which will eventually cause more metal to be exposed. If chloride ions are present, as is the case with saltwater, meanwhile, the oxygen atoms combine with metallic atoms to form the destructive oxide compound. As the atoms combine, they weaken the metal, making the structure brittle, when impure iron is in contact with water, oxygen, other strong oxidants, or acids, it rusts. If salt is present, for example in seawater or salt spray, iron metal is relatively unaffected by pure water or by dry oxygen. As with other metals, like aluminium, a tightly adhering oxide coating, the conversion of the passivating ferrous 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 hydroxide species are formed. Unlike ferrous oxides, the hydroxides do not adhere to the bulk metal, when iron rusts, the oxides take up more volume than the original metal, this expansion can generate enormous forces, damaging structures made with iron. See Economic effect for more details, the rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen
12.
Electroplating
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Electroplating is a process that uses electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. The term is used for electrical oxidation of anions onto a solid substrate. Electroplating is primarily used to change the properties of an object. The process used in electroplating is called electrodeposition and it is analogous to a galvanic cell acting in reverse. The part to be plated is the cathode of the circuit, in one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that it comprises, at the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they plate out onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated, in this manner, the ions in the electrolyte bath are continuously replenished by the anode. Other electroplating processes may use a non-consumable anode such as lead or carbon, in these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution. The most common form of electroplating is used for creating coins such as pennies, the cations associate with the anions in the solution. These cations are reduced at the cathode to deposit in the metallic, for example, for copper plating, in an acid solution, copper is oxidized at the anode to Cu2+ by losing two electrons. The Cu2+ associates with the anion SO42− in the solution to form copper sulfate, at the cathode, the Cu2+ is reduced to metallic copper by gaining two electrons. The result is the transfer of copper from the anode source to a plate covering the cathode. The plating is most commonly a metallic element, not an alloy. However, some alloys can be electrodeposited, notably brass and solder, many plating baths include cyanides of other metals in addition to cyanides of the metal to be deposited. These free cyanides facilitate anode corrosion, help to maintain a constant metal ion level, additionally, non-metal chemicals such as carbonates and phosphates may be added to increase conductivity. When plating is not desired on certain areas of the substrate, typical stop-offs include tape, foil, lacquers, and waxes. The ability of a plating to cover uniformly is called throwing power, initially, a special plating deposit called a strike or flash may be used to form a very thin plating with high quality and good adherence to the substrate
