![Inside of a tin platted can](https://upload.wikimedia.org/wikipedia/commons/5/58/Inside_of_a_tin_platted_can.jpg)
Tinning is the process of thinly coating sheets of
wrought iron
Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...
or
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
with
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
, and the resulting product is known as
tinplate
Tinplate consists of sheets of steel coated with a thin layer of tin to impede rusting. Before the advent of cheap milled steel, the backing metal was wrought iron. While once more widely used, the primary use of tinplate now is the manufacture of ...
. The term is also widely used for the different process of coating a metal with
solder
Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...
before soldering.
It is most often used to prevent
rust
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH ...
, but is also commonly applied to the ends of
stranded wire used as
electrical conductor
In physics and electrical engineering, a conductor is an object or type of material that allows the flow of charge (electric current) in one or more directions. Materials made of metal are common electrical conductors. Electric current is gener ...
s to prevent
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
(which increases
electrical resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...
), and to keep them from fraying or unraveling when used in various
wire connectors like
twist-ons,
binding post
A binding post is a connector commonly used on electronic test equipment to terminate (attach) a single wire or test lead. They are also found on loudspeakers and audio amplifiers as well as other electrical equipment.
History
A binding po ...
s, or
terminal block
A screw terminal is a type of electrical connection where a wire is held by the tightening of a screw.
Description
The wire may be wrapped directly under the head of a screw, may be held by a metal plate forced against the wire by a screw, or ...
s, where stray strands can cause a
short circuit
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...
.
While once more widely used, the primary use of tinplate now is the manufacture of
tin can
A steel can, tin can, tin (especially in British English, Australian English, Canadian English and South African English),
steel packaging, or can is a container for the distribution or storage of goods, made of thin metal. Many cans re ...
s. Formerly, tinplate was used for cheap pots, pans, and other
holloware
Holloware (hollowware, or hollow-ware ) is metal tableware such as sugar bowls, creamers, coffee pots, teapots, soup tureens, hot food covers, water jugs, platters, butter pat plates, and other items that accompany dishware on a table. It d ...
. This kind of holloware was also known as
tinware
Tinware is any item made of prefabricated tinplate. Usually tinware refers to kitchenware made of tinplate, often crafted by tinsmiths. Many cans used for canned food are tinware as well. Something that is tinned after being shaped and fabricated i ...
and the people who made it were tinplate workers.
The untinned sheets employed in the manufacture are known as black plates. They are now made of steel, either
Bessemer steel or open-hearth. Formerly
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
was used, and was of two grades,
coke iron and
charcoal iron
Charcoal iron is the substance created by the smelting of iron ore with charcoal.
All ironmaking blast furnaces were fueled by charcoal until Abraham Darby introduced coke as a fuel in 1709. The more economical coke soon replaced charcoal in Bri ...
; the latter, being the better, received a heavier coating of tin, and this circumstance is the origin of the terms coke plates and charcoal plates by which the quality of tinplate is still designated, although iron is no longer used. Tinplate was consumed in enormous quantities for the manufacture of the tin cans in which preserved
meat
Meat is animal flesh that is eaten as food. Humans have hunted, farmed, and scavenged animals for meat since prehistoric times. The establishment of settlements in the Neolithic Revolution allowed the domestication of animals such as chic ...
,
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
,
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
,
biscuit
A biscuit is a flour-based baked and shaped food product. In most countries biscuits are typically hard, flat, and unleavened. They are usually sweet and may be made with sugar, chocolate, icing, jam, ginger, or cinnamon. They can also be ...
s,
cigarette
A cigarette is a narrow cylinder containing a combustible material, typically tobacco, that is rolled into thin paper for smoking. The cigarette is ignited at one end, causing it to smolder; the resulting smoke is orally inhaled via the opp ...
s, and numerous other products are packed, and also for the household utensils of various kinds made by the
tinsmith
A tinsmith is a person who makes and repairs things made of tin or other light metals. The profession may sometimes also be known as a tinner, tinker, tinman, or tinplate worker; whitesmith may also refer to this profession, though the same wo ...
.
History
The practice of tinning ironware to protect it against rust is an ancient one. According to
Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
tinning was invented by the
Gallic Bituriges The Gaulish name Bituriges, meaning 'kings of the world', can refer to:
* Bituriges Cubi, an ancient Gallic tribe dwelling around modern Bourges
* Bituriges Vivisci, an ancient Gallic tribe dwelling around modern Bordeaux
{{Disambiguation ...
tribe (based near modern
Bourges
Bourges () is a commune in central France on the river Yèvre. It is the capital of the department of Cher, and also was the capital city of the former province of Berry.
History
The name of the commune derives either from the Bituriges, t ...
), who boiled copper objects in a tin solution in order to make them look as if they were made from silver. The first detailed account of the process appears in
Zosimus of Panopolis
Zosimos of Panopolis ( el, Ζώσιμος ὁ Πανοπολίτης; also known by the Latin name Zosimus Alchemista, i.e. "Zosimus the Alchemist") was a Greco-Egyptian alchemist and Gnostic mystic who lived at the end of the 3rd and beginning ...
, Book 6.62, part of a work on
alchemy
Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
written in
Roman Egypt
, conventional_long_name = Roman Egypt
, common_name = Egypt
, subdivision = Province
, nation = the Roman Empire
, era = Late antiquity
, capital = Alexandria
, title_leader = Praefectus Augustalis
, image_map = Roman E ...
around 300 AD. Aside from an attestation in 14th century England, the process is not attested again in Europe until the description in
Lazarus Ercker
Lazarus Ercker (c. 1530 – 1594) was a Bohemian metallurgist and assay master of a mint near Prague who wrote some of the earliest known treatises on metallurgy entitled ''Beschreibung allerfürnemisten mineralischen Ertzt und Berckwercksarten'' ...
's ''Das Kleine Probierbuch'' (1556)
The manufacture of tinplate was long a
monopoly
A monopoly (from Greek language, Greek el, μόνος, mónos, single, alone, label=none and el, πωλεῖν, pōleîn, to sell, label=none), as described by Irving Fisher, is a market with the "absence of competition", creating a situati ...
of
Bohemia
Bohemia ( ; cs, Čechy ; ; hsb, Čěska; szl, Czechy) is the westernmost and largest historical region of the Czech Republic. Bohemia can also refer to a wider area consisting of the historical Lands of the Bohemian Crown ruled by the Bohem ...
, but in about the year 1620 the industry spread to
Saxony
Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...
. Tinplate was apparently produced in the 1620s at a mill of (or under the patronage of) the Earl of Southampton, but it is not clear how long this continued.
Andrew Yarranton
Andrew Yarranton (1619–1684) was an important English engineer in the 17th century who was responsible for making several rivers into navigable waterways.
Biography
He was born at Astley, just south of the town of Stourport-on-Severn in Worce ...
, an English
engineer
Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...
and agriculturist, and
Ambrose Crowley Sir Ambrose Crowley III (1 April 1657/8''England & Wales, Quaker Birth, Marriage, and Death Registers, 1578-1837'' – 17 October 1713) was a 17th-century English ironmonger and politician who was returned to the House of Commons in 1713.
Early ye ...
(a Stourbridge blacksmith and father of the more famous
Sir Ambrose Crowley III) were commissioned to go to Saxony and if possible discover the methods employed. They visited Dresden in 1667 and found out how it was made. In doing so, they were sponsored by various local
ironmaster
An ironmaster is the manager, and usually owner, of a forge or blast furnace for the processing of iron. It is a term mainly associated with the period of the Industrial Revolution, especially in Great Britain.
The ironmaster was usually a large ...
s and people connected with the project to make the
River Stour navigable. In Saxony, the plates were forged, but when they conducted experiments on their return to England, they tried rolling the iron. This led to two of the sponsors, the ironmasters
Philip Foley
Philip Foley (12 May 1648 – December 1716) was the youngest of the three surviving sons of the British ironmaster Thomas Foley. His father transferred all his ironworks in the Midlands to him in 1668 and 1669 for £60,000. He also settled an ...
and
Joshua Newborough, erecting a new mill,
Wolverley
Wolverley is a village; with nearby Cookley (1 mi northeast), it forms a civil parish in the Wyre Forest District of Worcestershire, England. It is 2 miles north of Kidderminster and lies on the River Stour and the Staffordshire and ...
Lower Mill (or forge), in 1670. This contained three shops: one being a
slitting mill
The slitting mill was a watermill for slitting bars of iron into rods. The rods then were passed to nailers who made the rods into nails, by giving them a point and head.
The slitting mill was probably invented near Liège in what is now Belg ...
, which would serve as a
rolling mill
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
, the others being forges. In 1678 one of these was making
frying pan
A frying pan, frypan, or skillet is a flat-bottomed pan used for frying, searing, and browning foods. It is typically in diameter with relatively low sides that flare outwards, a long handle, and no lid. Larger pans may have a small grab han ...
s and the other drawing out
blooms made in
finery forge
A finery forge is a forge used to produce wrought iron from pig iron by decarburization in a process called "fining" which involved liquifying cast iron in a fining hearth and removing carbon from the molten cast iron through oxidation. Finery ...
s elsewhere. It is likely that the intention was to roll the plates and then finish them under a hammer, but the plan was frustrated by one William Chamberlaine renewing a
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
granted to him and
Dud Dudley
Dudd (Dud) Dudley (1600–1684) was an English metallurgist, who fought on the Royalist side in the English Civil War as a soldier, military engineer, and supplier of munitions. He was one of the first Englishmen to smelt iron ore using coke.
B ...
in 1662. Yarranton described the patent as "trumped up".
The slitter at
Wolverley
Wolverley is a village; with nearby Cookley (1 mi northeast), it forms a civil parish in the Wyre Forest District of Worcestershire, England. It is 2 miles north of Kidderminster and lies on the River Stour and the Staffordshire and ...
was Thomas Cooke. Another Thomas Cooke, perhaps his son, moved to
Pontypool
Pontypool ( cy, Pont-y-pŵl ) is a town and the administrative centre of the county borough of Torfaen, within the historic boundaries of Monmouthshire in South Wales. It has a population of 28,970.
Location
It is situated on the Afon Lwyd ri ...
and worked there for
John Hanbury (1664–1734)
John Hanbury, Esq. (1664–1734) was a British ironmaster and politician who sat in the House of Commons between 1701 and 1734. He was one of a dynasty of ironmasters responsible for the industrialisation and urbanisation of the eastern valley th ...
. According to
Edward Lhuyd
Edward Lhuyd FRS (; occasionally written Llwyd in line with modern Welsh orthography, 1660 – 30 June 1709) was a Welsh naturalist, botanist, linguist, geographer and antiquary. He is also named in a Latinate form as Eduardus Luidius.
Life
...
, by 1697, John Hanbury had a rolling mill at
Pontypool
Pontypool ( cy, Pont-y-pŵl ) is a town and the administrative centre of the county borough of Torfaen, within the historic boundaries of Monmouthshire in South Wales. It has a population of 28,970.
Location
It is situated on the Afon Lwyd ri ...
for making "Pontypoole Plates" machine. This has been claimed as a tinplate works, but it was almost certainly only producing (untinned)
blackplate. However, this method of rolling iron plates by means of cylinders, enabled more uniform black plates to be produced than was possible with the old plan of
hammer
A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as w ...
ing, and in consequence the English tinplate became recognised as superior to the
German
German(s) may refer to:
* Germany (of or related to)
** Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
.
![Trefforrest tin works, Glamorganshire](https://upload.wikimedia.org/wikipedia/commons/d/d4/Trefforrest_tin_works%2C_Glamorganshire.jpeg)
Tinplate first begins to appear in the Gloucester Port Books (which record trade passing through
Gloucester
Gloucester ( ) is a cathedral city and the county town of Gloucestershire in the South West of England. Gloucester lies on the River Severn, between the Cotswolds to the east and the Forest of Dean to the west, east of Monmouth and east ...
, mostly from ports in the
Bristol Channel
The Bristol Channel ( cy, Môr Hafren, literal translation: "Severn Sea") is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Seve ...
) in 1725. The tinplate was shipped from
Newport, Monmouthshire
Newport ( cy, Casnewydd; ) is a city and county borough in Wales, situated on the River Usk close to its confluence with the Severn Estuary, northeast of Cardiff. With a population of 145,700 at the 2011 census, Newport is the third-largest au ...
. This immediately follows the first appearance (in
French) of
Réaumur's ''Principes de l'art de fer-blanc'', and prior to a report of it being published in England.
Further mills followed a few years later, initially in many ironmaking regions in England and Wales, but later mainly in south Wales. In 1805, 80,000 boxes were made and 50,000 exported. The industry continued to spread steadily in England and especially
Wales
Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...
, and after 1834 its expansion was rapid,
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
becoming the chief source of the world's supply. In that year her total production was 180,000 boxes of 108 lb each (around 50 kg, in America a box is 100 lb), in 1848 it was 420,000 boxes, in 1860 it reached 1,700,000 boxes. But subsequently the advance was rapid, and the production reached about 2,236,000 lb in 1891. One of the greatest markets was the United States of America, but that market was cut off in 1891, when the
McKinley tariff
The Tariff Act of 1890, commonly called the McKinley Tariff, was an act of the United States Congress, framed by then Representative William McKinley, that became law on October 1, 1890. The tariff raised the average duty on imports to almost fift ...
was enacted there. This caused a great retrenchment in the British industry and the emigration to America of many of those who could no longer be employed in the surviving tinplate works.
In 1891, the United States made 11,000 tons of tinplate and imported 325,100 tons, but in 1899, it made 360,900 tons, importing only 63,500 tons (mostly for re-export). British exports were further hindered by the Dingley tariff, which removed the advantage of Welsh plate on America's Pacific coast, had by 1900 increased to more than 849,000,000 lb, of which over 141,000,000 lb were terne-plates. The total imports in that year were only 135,264,881 lb. In later years, again, there was a decline in the American production, and in 1907 only 20% of the American tinplate mills were at work, while the British production reached 14 million boxes.
Despite this blow, the industry continued, but on a smaller scale. Nevertheless, there were still 518 mills in operation in 1937, including 224 belonging to
Richard Thomas & Co. However the traditional 'pack mill' had been overtaken by the improved 'strip mill', of which the first in
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
was built by Richard Thomas & Co. in the late 1930s. Strip mills rendered the old pack mills obsolete and the last of them closed in about the 1960s.
Plate production methods
The pack mill process
The pack mill process begins with a ''tin bar'', which is a drawn flat bar that was usually purchased from an
ironworks
An ironworks or iron works is an industrial plant where iron is smelted and where heavy iron and steel products are made. The term is both singular and plural, i.e. the singular of ''ironworks'' is ''ironworks''.
Ironworks succeeded bloomeri ...
or
steel works
A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-finis ...
. The tin bar could be
wrought iron
Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...
or
mild steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt ...
. The cross-section of the bar needed to be accurate in size as this dictates the length and thickness of the final plates. The bar was cut to the correct length to make the desired size plate. For instance, if a plate is desired the tin bar is cut to a length and width that is divisible by 14 and 20. The bar is then rolled and doubled over, with the number of times being doubled over dependent on how large the tin bar is and what the final thickness is. If the starting tin bar is then it must be at least finished on the ''fours'', or doubled over twice, and if a thin gauge is required then it may be finished on the ''eights'', or doubled over three times. The tin bar is then heated to a dull
red heat
The practice of using colours to determine the temperature of a piece of (usually) ferrous metal comes from blacksmithing. Long before thermometers were widely available it was necessary to know what state the metal was in for heat treating it an ...
and passed five or six times through the roughing rolls. Between each pass the plate is passed over (or round) the rolls, and the gap between the rolls is narrowed by means of a screw. The plate is then reheated and run through the finishing rolls.
If the plate is not finished on ''singles'', or without doubling the plate over, it is doubled over in a
squeezer. The squeezer was like a table where one half of the surface folds over on top of the other and a press flattens the doubled over plate so the rolled end will fit in the rollers. It is then reheated for another set of rolling. This is repeated until the desired geometry is reached. Note that if the plate needs to be doubled over more than once the rolled end is sheared off. The pack is then allowed to cool. When cool, the pack is sheared slightly undersized from the final dimensions and the plates separated by ''openers''.
At this point, the plates are covered in
scale and must be
pickled
Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called ...
. This involves dipping the plates in sulfuric acid for five minutes. The pickling turns the scales into a greenish-black slime which is removed via annealing. The plates are annealed for approximately 10 hours and then allowed to slowly cool. At this point the plates are known as ''pickled and annealed black plates''. These plates were commonly sold for
stamping and
enameling
Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between . The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word comes from the Latin ...
purposes.
After this, the plates are rough and not straight, so they are
cold rolled
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
several times. The rolling lengthens the plates to their final dimension. They are then annealed again to remove any
strain hardening
In materials science, work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context.
This strength ...
. These plates are called ''black plate pickled, cold rolled, and close annealed'' (black plate p. cr. and ca.). To attain perfect cleanliness the plates are pickled again in a weak
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
. Finally they are rinsed and stored in water until ready to be tinned.
The tinning set consists of at least one pot of molten tin, with a
zinc chloride
Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and ev ...
flux on top, and a grease pot. The flux dries the plate and prepares it for the tin to adhere. If a second tin pot is used, called the ''wash pot'', it contains tin at a lower temperature. This is followed by the grease pot, which contains oil and a ''tinning machine''. The tinning machine has two small rollers that are spring-loaded together so that when the tinned plate is inserted the rolls squeeze off any excess tin. The springs on the tinning machine can be set to different forces to give different thicknesses of tin. Finally, the oil is cleaned off with fine
bran
Bran, also known as miller's bran, is the hard outer layers of Cereal, cereal grain. It consists of the combined aleurone and pericarp. Corn (maize) bran also includes the pedicel (tip cap). Along with cereal germ, germ, it is an integral pa ...
and dusted clean.
What is described here is the process as employed during the 20th century. The process grew somewhat in complexity over time, as it was found that the inclusion of additional procedures improved quality. The practice of
hot rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
and then
cold rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
evidently goes back to the early days, as the Knight family's tinplate works had (from its foundation in about 1740) two rolling mills, one at Bringewood (west of Ludlow) which made
blackplate, and the other the tin mill at Mitton (now part of
Stourport
Stourport-on-Severn, often shortened to Stourport, is a town and civil parish in the Wyre Forest District of North Worcestershire, England, a few miles to the south of Kidderminster and downstream on the River Severn from Bewdley. At the 2011 ce ...
, evidently for the later stages.
[L. Ince, ''The Knight family and the British Iron Industry'' (1991).]
The strip mill
Early
hot rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
strip mills did not produce strip suitable for tinning, but in 1929
cold rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
began to be used to reduce the gauge further, which made tinning achievable. The plate was then tinned using the process outlined above.
Tinning processes
There are two processes for the tinning of the black plates: hot-dipping and
electroplating
Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the reduction of cations of that metal by means of a direct electric current. The part to be ...
.
Hot-dipping
Hot Tin-dipping is the process of immersing a part into a bath of pure molten tin at a temperature greater than 450°F or 232°C.
Tinplate made via hot-dipped tin plating is made by
cold rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
steel or iron,
pickling
Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is called a ...
to remove any
scale,
annealing to remove any
strain hardening
In materials science, work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context.
This strength ...
, and then coating it with a thin layer of
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
. Originally this was done by producing individual or small packs of plates, which became known as the ''pack mill process''. In the late 1920s ''strip mills'' began to replace pack mills, because they could produce the raw plates in larger quantities and more economically.
Electroplating
In electroplating, the item to be coated is placed into a container containing a solution of one or more tin salts. The item is connected to an
electrical circuit
An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage sources, ...
, forming the
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...
(negative) of the circuit while an electrode typically of the same metal to be plated forms the
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic is ...
(positive). When an
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
is passed through the circuit, metal
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
s in the solution are attracted to the item. To produce a smooth, shiny surface, the electroplated sheet is then briefly heated above the melting point of tin. Most of the tin-plated steel made today is then further electroplated with a very thin layer of
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hardne ...
to prevent dulling of the surface from oxidation of the tin.
Alternatives
*Terne-plate is a similar product to tinplate, but the bath is not of tin, but of tin and
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
mixed, the latter metal constituting from 7.59% of the whole. The name derives from "terne", meaning dull or
tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, aluminum, magnesium, neodymium and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in ...
. Terne-plates began to be produced in
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
about the middle of the 19th century, and became widely employed in the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
for roofing purposes. Other applications included fuel tanks and gas meters. The last Terne-plate mill in Brockmoor, West Midlands in the UK was closed in 200
*For many purposes, tinplate has been replaced by
galvanization, galvanised (
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
-coated) vessels - though not for cooking, as zinc can be toxic. Zinc protects iron
electrolytically, that is, the zinc will oxidise and turn to a white powder to preserve the iron, whereas tin will only protect the iron if the tin-surface remains unbroken, as it electrolytically cannibalises unprotected iron to preserve itself.
See also
*
Blackplate
*
Kalai (process), a form of tinning practiced in India
*
Plating
Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improv ...
for other processes for plating metals
*
Sherardizing
*
Tinsmith
A tinsmith is a person who makes and repairs things made of tin or other light metals. The profession may sometimes also be known as a tinner, tinker, tinman, or tinplate worker; whitesmith may also refer to this profession, though the same wo ...
*
Tinware
Tinware is any item made of prefabricated tinplate. Usually tinware refers to kitchenware made of tinplate, often crafted by tinsmiths. Many cans used for canned food are tinware as well. Something that is tinned after being shaped and fabricated i ...
*
Black oxide
Black oxide or blackening is a conversion coating for ferrous materials, stainless steel, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance, for appearance, and to minimize light ...
References
Bibliography
*
*
*
*
*
*{{cite journal , last1=Welter , first1=J.-M. , title=Contact tinning: A millennia-old plating technology , journal=Archaeometry , date=2019 , volume=61 , issue=4 , pages=906–920 , doi=10.1111/arcm.12454 , s2cid=134869188
Further reading
*F. W. Gibbs, 'The rise of the tinplate industry' ''Annals of Science'' 6 (1950), 390ff; 7(1) (1951), 25ff; 43ff; 113ff.
*P. Jenkins, Twenty by Fourteen': a history of the south Wales tinplate industry 1700-1961'' (Gomer, Llandysul, Dyfed 1995).
*D.A. Irwin, 'Did late nineteenth century U.S. tariffs promote infant industries? Evidence from the tinplate industry' (NBER working paper 6835 1998)
Coatings
Industrial processes
Metal plating
Metallurgical processes
Steelmaking
Thin film deposition
Tin