Editing Electroplating

{{Short description|Electrochemical process for coating with metal}}
[[File:PCB copper layer electroplating machine.jpg|thumb|upright=1.25|Copper electroplating machine for layering [[Printed circuit board|PCBs]]]]

'''Electroplating''', also known as '''electrochemical deposition''' or '''electrodeposition''', is a process for producing a [[metal]] coating on a solid substrate through the [[redox|reduction]] of [[cation]]s of that metal by means of a [[direct current|direct electric current]]. The part to be coated acts as the [[cathode]] (negative [[electrode]]) of an [[electrolytic cell]]; the [[electrolyte]] is a [[solution (chemistry)|solution]] of a [[salt (chemistry)|salt]] whose cation is the metal to be coated, and the [[anode]] (positive electrode) is usually either a block of that metal, or of some inert [[electrical conductor|conductive]] material.  The current is provided by an external [[power supply]].

Electroplating is widely used in industry and [[decorative art]]s to improve the surface qualities of objects—such as resistance to [[abrasion (mechanical)|abrasion]] and [[corrosion]], [[lubrication|lubricity]], [[reflectivity]], [[electrical conductivity]], or appearance.  It is used to build up thickness on undersized or worn-out parts and to manufacture metal plates with complex shape, a process called [[electroforming]]. It is used to deposit copper and other conductors in forming [[printed circuit boards]] and [[copper interconnects]] in integrated circuits. It is also used to purify metals such as [[copper]].

The aforementioned electroplating of metals uses an electroreduction process (that is, a negative or [[cathodic]] current is on the working electrode). The term "electroplating" is also used occasionally for processes that occur under electro-oxidation (i.e positive or [[anodic]] current on the working electrode), although such processes are more commonly referred to as [[anodizing]] rather than electroplating. One such example is the formation of [[silver chloride]] on silver wire in [[chloride]] solutions to make [[silver chloride electrode|silver/silver-chloride (AgCl) electrodes]].

[[Electropolishing]], a process that uses an electric current to selectively remove the outermost layer from the surface of a metal object, is the reverse of the process of electroplating.<ref>{{Cite web |url=https://www.electro-glo.com/faqs/ |title=FAQs &#124; Frequently Asked Questions &#124; Electropolishing &#124;&#124; Electro-Glo |access-date=2019-05-01 |archive-date=2020-11-28 |archive-url=https://web.archive.org/web/20201128185604/https://www.electro-glo.com/faqs/ |url-status=live }}</ref>

''[[Throwing power]]'' is an important parameter that provides a measure of the uniformity of electroplating current, and consequently the uniformity of the electroplated metal thickness, on regions of the part that are near to the anode compared to regions that are far from it. It depends mostly on the composition and temperature of the electroplating solution, as well as on the operating [[current density]].<ref name="Farber 1930">{{cite journal |last1=Farber |first1=H. L. |title=Throwing Power in Chromium Plating |journal=Bureau of Standards Journal of Research |date=1930 |volume=3 |page=27 |doi=10.6028/jres.004.003 |url=https://nvlpubs.nist.gov/nistpubs/jres/4/jresv4n1p27_A2b.pdf |access-date=6 August 2023}}</ref>  A higher [[#Throwing power|throwing power]] of the plating bath results in a more uniform coating.<ref>{{Cite web|title=Pollution Prevention Technology Profile Trivalent Chromium Replacements for Hexavalent Chromium Plating |publisher=Northeast Waste Management Officials’ Association |date=2003-10-18 |url=http://www.newmoa.org/prevention/p2tech/TriChromeFinal.pdf |archive-url=https://web.archive.org/web/20110720153833/http://www.newmoa.org/prevention/p2tech/TriChromeFinal.pdf |archive-date=2011-07-20 |url-status=dead }}</ref>

==Process==
[[File:Copper electroplating principle (multilingual).svg|thumb|upright|Simplified diagram for electroplating copper (orange) on a conductive object (the cathode, "Me", gray). The electrolyte is a solution of copper sulfate, {{chem|CuSO|4}} in [[sulfuric acid]]. A copper anode is used to replenish the electrolyte with copper cations {{chem|Cu|2+}} as they are plated out at the cathode.]]
{{See also|Electrotyping|Electroforming}}

The electrolyte in the electrolytic plating cell should contain positive ions (cations) of the metal to be deposited. These cations are reduced at the cathode to the metal in the zero valence state. For example, the electrolyte for [[copper electroplating]] can be a solution of [[copper(II) sulfate]], which dissociates into Cu<sup>2+</sup> cations and {{chem|SO|4|2-}} anions. At the cathode, the Cu<sup>2+</sup> is reduced to metallic copper by gaining two electrons.

When the anode is made of the metal that is intended for coating onto the cathode, the opposite reaction may occur at the anode, turning it into dissolved cations.  For example, [[copper]] would be oxidized at the anode to Cu<sup>2+</sup> by losing two electrons. In this case, the rate at which the anode is dissolved will equal the rate at which the cathode is plated, and thus the ions in the electrolyte bath are continuously replenished by the anode. The net result is the effective transfer of metal from the anode to the cathode.{{sfn|Dufour|2006|p=IX-1}}

The anode may instead be made of a material that resists electrochemical oxidation, such as [[lead]] or [[carbon]]. [[Oxygen]], [[hydrogen peroxide]], and some other byproducts are then produced at the anode instead. In this case, ions of the metal to be plated must be replenished (continuously or periodically) in the bath as they are drawn out of the solution.<ref name="Dufour, IX-2">{{harvnb|Dufour|2006|p=IX-2}}</ref>

The plating is most commonly a single metallic [[chemical element|element]], not an [[alloy]]. However, some alloys can be electrodeposited, notably [[brass]] and [[solder]]. Plated "alloys" are not "true alloys" (solid solutions), but rather they are tiny crystals of the elemental metals being plated. In the case of plated solder, it is sometimes deemed necessary to have a true alloy, and the plated solder is melted to allow the tin and lead to combine into a true alloy. The true alloy is more corrosion-resistant than the as-plated mixture.

Many plating baths include [[cyanide]]s of other metals (such as [[potassium cyanide]]) in addition to cyanides of the metal to be deposited. These free cyanides facilitate anode corrosion, help to maintain a constant metal ion level, and contribute to conductivity. Additionally, non-metal chemicals such as [[carbonate]]s and [[phosphate]]s may be added to increase conductivity.

When plating is not desired on certain areas of the substrate, ''stop-offs'' are applied to prevent the bath from coming in contact with the substrate. Typical stop-offs include tape, foil, [[lacquer]]s, and [[wax]]es.<ref name="dufour3">{{harvnb|Dufour |2006|p=IX-3}}</ref>

===Strike===
Initially, a special plating deposit called a ''strike'' or ''flash'' may be used to form a very thin (typically less than 0.1&nbsp;μm thick) plating with high quality and good adherence to the substrate. This serves as a foundation for subsequent plating processes. A strike uses a high current density and a bath with a low ion concentration. The process is slow, so more efficient plating processes are used once the desired strike thickness is obtained.

The striking method is also used in combination with the plating of different metals. If it is desirable to plate one type of deposit onto a metal to improve corrosion resistance but this metal has inherently poor adhesion to the substrate, then a strike can be first deposited that is compatible with both. One example of this situation is the poor adhesion of electrolytic [[nickel]] on [[zinc]] alloys, in which case a copper strike is used, which has good adherence to both.<ref name="Dufour, IX-2"/>

===Pulse electroplating===
{{See also|Pulse electrolysis}}
The pulse electroplating or pulse electrodeposition (PED) process involves the swift alternating of the [[electrical potential]] or [[Electric current|current]] between two different values, resulting in a series of pulses of equal amplitude, duration, and polarity, separated by zero current. By changing the pulse amplitude and width, it is possible to change the deposited film's composition and thickness.<ref>{{cite journal|last1=kunji durai|first1=M. S.|first2=Mathy|last2=chaala|title=Pulse and pulse reverse plating—Conceptual, advantages and applications|journal=Electrochimica Acta|volume=53|issue=8|year=2008|pages=3313–3322|doi=10.1016/j.electacta.2007.11.054}}</ref>

The experimental parameters of pulse electroplating usually consist of peak current/potential, duty cycle, frequency, and effective current/potential. Peak current/potential is the maximum setting of electroplating current or potential. Duty cycle is the effective portion of time in a certain electroplating period with the current or potential applied. The effective current/potential is calculated by multiplying the duty cycle and peak value of the current or potential. Pulse electroplating could help to improve the quality of electroplated film and release the internal stress built up during fast deposition. A combination of the short duty cycle and high frequency could decrease surface cracks. However, in order to maintain the constant effective current or potential, a high-performance power supply may be required to provide high current/potential and a fast switch. Another common problem of pulse electroplating is that the anode material could get plated and contaminated during the reverse electroplating, especially for a high-cost, inert electrode such as [[platinum]].

Other factors that affect the pulse electroplating include temperature, anode-to-cathode gap, and stirring. Sometimes, pulse electroplating can be performed in a heated electroplating bath to increase the deposition rate, since the rate of most chemical reactions increases exponentially with temperature per the [[Arrhenius equation|Arrhenius law]]. The anode-to-cathode gap is related to the current distribution between anode and cathode. A small gap-to-sample-area ratio may cause uneven distribution of current and affect the surface topology of the plated sample. Stirring may increase the transfer/diffusion rate of metal ions from the bulk solution to the electrode surface. The ideal stirring setting varies for different metal electroplating processes. 

===Brush electroplating===
A closely-related process is brush electroplating, in which localized areas or entire items are plated using a brush saturated with plating solution. The brush, typically a [[graphite]] body wrapped with an absorbent [[cloth]] material that both holds the plating solution and prevents direct contact with the item being plated, is connected to the [[anode]] of a low-voltage and 3-4 ampere [[direct current|direct-current]] power source, and the item to be plated (the [[cathode]]) is grounded. The operator dips the brush in plating solution and then applies it to the item, moving the brush continually to get an even distribution of the plating material.

Brush electroplating has several advantages over tank plating, including portability, the ability to plate items that for some reason cannot be tank plated (one application was the plating of portions of very large decorative support columns in a building restoration), low or no masking requirements, and comparatively low plating solution volume requirements. Mainly used industrially for part repair, worn bearing surfaces getting a nickel or silver deposit. With technological advancement deposits up to .025" have been achieved and retained uniformity. Disadvantages compared to tank plating can include greater operator involvement (tank plating can frequently be done with minimal attention and the solutions used are often toxic), and the inconsistency in achieving as great a plate thickness.

===Barrel plating===
{{main article|Barrel plating}}
This technique of electroplating is one of the most common used in the industry for large numbers of small objects. The objects are placed in a barrel-shaped non-conductive cage and then immersed in a chemical bath containing dissolved ions of the metal that is to be plated onto them.  The barrel is then rotated, and electrical currents are run through the various pieces in the barrel, which complete circuits as they touch one another. The result is a very uniform and efficient plating process, though the finish on the end products will likely suffer from abrasion during the plating process. It is unsuitable for highly ornamental or precisely engineered items.<ref name="Tan1992">{{cite book|author=A.C. Tan|title=Tin and Solder Plating in the Semiconductor Industry|url=https://books.google.com/books?id=DyrohYlFCiYC&pg=PA122|date=30 November 1992|publisher=Springer Science & Business Media|isbn=978-0-412-48240-3|page=122|access-date=16 May 2019|archive-date=1 August 2020|archive-url=https://web.archive.org/web/20200801074731/https://books.google.com/books?id=DyrohYlFCiYC&pg=PA122|url-status=live}}</ref>

=== Cleanliness ===
[[Parts cleaning|Cleanliness]] is essential to successful electroplating, since molecular layers of [[oil]] can prevent adhesion of the coating. [[ASTM]] B322 is a standard guide for cleaning metals prior to electroplating. Cleaning includes solvent cleaning, hot alkaline detergent cleaning, electrocleaning, [[ultrasonic cleaning]] and acid treatment. The most common industrial test for cleanliness is the waterbreak test, in which the surface is thoroughly rinsed and held vertical. [[Hydrophobic]] contaminants such as oils cause the water to bead and break up, allowing the water to drain rapidly. Perfectly clean metal surfaces are [[hydrophilic]] and will retain an unbroken sheet of water that does not bead up or drain off. ASTM F22 describes a version of this test. This test does not detect hydrophilic contaminants, but electroplating can displace these easily, since the solutions are water-based. [[Surfactant]]s such as [[soap]] reduce the sensitivity of the test and must be thoroughly rinsed off.

==Test cells and characterization==

===Throwing power===
''Throwing power'' (or ''macro throwing power'') is an important parameter that provides a measure of the uniformity of electroplating current, and consequently the uniformity of the electroplated metal thickness, on regions of the part that are near the anode compared to regions that are far from it. It depends mostly on the composition and temperature of the electroplating solution.<ref name="Farber 1930" /> ''Micro throwing power'' refers to the extent to which a process can fill or coat small recesses such as [[Through-hole technology|through-holes]].<ref name="McCormick+Kuhn 1993">{{cite journal | last1=McCormick | first1=M. | last2=Kuhn | first2=A. T. | title=The Haring-Blum Cell | journal=Transactions of the IMF | volume=71 | issue=2 | year=1993 | issn=0020-2967 | doi=10.1080/00202967.1993.11870992 | pages=74–76}}</ref> Throwing power can be characterized by the dimensionless [[Wagner number]]:

<math display="block">\text{Wa} = \frac{RT\kappa}{FL\alpha|i|},</math>

where ''R'' is the [[universal gas constant]], ''T'' is the operating [[temperature]], ''κ'' is the ionic conductivity of the plating solution, ''F'' is the [[Faraday constant]], ''L'' is the equivalent size of the plated object, ''α'' is the [[charge transfer coefficient|transfer coefficient]], and ''i'' the surface-averaged total (including [[hydrogen evolution]]) current density.  The Wagner number quantifies the ratio of kinetic to ohmic resistances.  A higher Wagner number produces a more uniform deposition.  This can be achieved in practice by decreasing the size (''L'') of the plated object, reducing the current density {{math|{{abs|''i''}}}}, adding chemicals that lower ''α'' (make the electric current less sensitive to voltage), and raising the solution conductivity (e.g. by adding [[acid]]). Concurrent [[hydrogen evolution]] usually improves the uniformity of electroplating by increasing {{math|{{abs|''i''}}}}; however, this effect can be offset by blockage due to hydrogen bubbles and hydroxide deposits.<ref>Fuller, T. F.; Harb, J. N. Electrochemical engineering; John Wiley & Sons, 2018. ISBN 9781119446583</ref> 

The Wagner number is rather difficult to measure accurately; therefore, other related parameters, that are easier to obtain experimentally with standard cells, are usually used instead. These parameters are derived from two ratios: the ratio {{math|''M'' {{=}} ''m''<sub>1</sub> / ''m''<sub>2</sub>}} of the plating thickness of a specified region of the cathode "close" to the anode to the thickness of a region "far" from the cathode and the ratio {{math|''L'' {{=}} ''x''<sub>2</sub> / ''x''<sub>1</sub>}} of the distances of these regions through the electrolyte to the anode.  In a Haring-Blum cell, for example, {{math|''L'' {{=}} 5}} for its two independent cathodes, and a cell yielding plating thickness ratio of ''M'' = 6 has Harring-Blum throwing power {{math|100% × (''L'' − ''M'') / ''L'' {{=}} −20%}}.<ref name="McCormick+Kuhn 1993" /> Other conventions include the Heatley throwing power {{math|100% × (''L'' − ''M'') / (''L'' − 1)}}, Field throwing power {{math|100% × (''L'' − ''M'') / (''L'' + ''M'' − 2)}},<ref name="Gabe 2002">{{cite journal | last=Gabe | first=David R. | title=Test cells for plating | journal=Metal Finishing | volume=100 | year=2002 | issn=0026-0576 | doi=10.1016/s0026-0576(02)82059-1 | pages=579–586}}</ref>  and Luke throwing power {{math|100% × ''L'' / (''L'' + ''M'' − 1)}}. A more uniform thickness is obtained by making the throwing power larger (less negative), except for Luke's throwing power, which has the advantage of having a minimum of 0 and a maximum of 100, in terms of the less negative value, according to any of these definitions.

Parameters that describe cell performance such as throwing power are measured in small test cells of various designs that aim to reproduce conditions similar to those found in the production plating bath.<ref name="McCormick+Kuhn 1993" />

===Haring–Blum cell===
[[File:Haring Cell.jpg|thumb|Haring–Blum cell]]

The Haring–Blum cell is used to determine the macro throwing power of a plating bath. The cell consists of two parallel cathodes with a fixed anode in the middle. The cathodes are at distances from the anode in the ratio of 1:5. The macro throwing power is calculated from the thickness of plating at the two cathodes when a [[direct current]] is passed for a specific period of time. The cell is fabricated out of [[perspex]] or glass.<ref>{{cite book|last1=Bard |first1=Allan |last2=Inzelt |first2=György |last3=Scholz |first3=Fritz |chapter=Haring–Blum Cell |page=444 |title=Electrochemical Dictionary|publisher= Springer|doi=10.1007/978-3-642-29551-5_8|year=2012|isbn=978-3-642-29551-5}}</ref><ref>{{cite book|page=122|title=Electrochemical Engineering: Science and Technology in Chemical and Other Industries|year=1999|last1=Wendt |first1=Hartmut |first2=Kreyse |last2=Gerhard|isbn=3540643869|publisher=Springer }}</ref>

===Hull cell===
[[Image:Hullcell.jpg|thumb|A zinc solution tested in a Hull cell]]
The [[Hull cell]] is a type of test cell used to semi-quantitatively check the condition of an electroplating bath. It measures useable current density range, optimization of additive concentration, recognition of impurity effects, and indication of macro throwing power capability.<ref>{{Cite book | title = Metal Finishing: Guidebook and Directory. Issue 98 | page = 588 | year = 1998 | volume = 95}}</ref> The Hull cell replicates the plating bath on a lab scale. It is filled with a sample of the plating solution and an appropriate anode which is connected to a [[rectifier]]. The "work" is replaced with a Hull cell test panel that will be plated to show the "health" of the bath.

The Hull cell is a trapezoidal container that holds 267 milliliters of a plating bath solution. This shape allows one to place the test panel on an angle to the anode. As a result, the deposit is plated at a range current densities along its length, which can be measured with a Hull cell ruler. The solution volume allows for a semi-quantitative measurement of additive concentration: 1&nbsp;gram addition to 267&nbsp;mL is equivalent to 0.5&nbsp;oz/gal in the plating tank.<ref>{{cite web|last=Kushner|first=Arthur S.|date=December 1, 2006|url=http://www.allbusiness.com/manufacturing/chemical-manufacturing-paint/3993213-1.html |url-status=dead |archive-url=https://web.archive.org/web/20100313093038/http://www.allbusiness.com/manufacturing/chemical-manufacturing-paint/3993213-1.html|archive-date=March 13, 2010 |title=Hull Cell 101 |website=Products Finishing}}</ref>

==Effects==
Electroplating changes the chemical, physical, and mechanical properties of the workpiece.  An example of a chemical change is when [[nickel]] plating improves corrosion resistance.  An example of a physical change is a change in the outward appearance. An example of a mechanical change is a change in [[tensile strength]] or surface [[hardness]], which is a required attribute in the tooling industry.<ref>{{cite book | first1 = Robert H. | last1 = Todd | first2 = Dell K. | last2 = Allen | first3 = Leo | last3 = Alting | year = 1994 | title = Manufacturing Processes Reference Guide | chapter = Surface Coating | publisher = Industrial Press | isbn = 0-8311-3049-0 | url = https://books.google.com/books?id=6x1smAf_PAcC | pages = 454–458 | url-status = live | archive-url = https://web.archive.org/web/20131009082958/http://books.google.com/books?id=6x1smAf_PAcC | archive-date = 2013-10-09 }}</ref>  Electroplating of acid gold on underlying copper- or nickel-plated circuits reduces contact resistance as well as surface hardness.  Copper-plated areas of mild steel act as a mask if [[case-hardening]] of such areas are not desired. Tin-plated steel is chromium-plated to prevent dulling of the surface due to oxidation of tin.

==Specific metals==
{{Further|Plating#Specific_cases}}

==Alternatives to electroplating==

There are a number of alternative processes to produce metallic coatings on solid substrates that do not involve electrolytic reduction:

* [[Electroless Deposition|Electroless deposition]] uses a bath containing metal ions and chemicals that will reduce them to the metal by [[redox reaction]]s.  The reaction should be [[autocatalysis|autocatalytic]], so that new metal will be deposited over the growing coating, rather than precipitated as a powder through the whole bath at once.  Electroless processes are widely used to deposit [[Electroless nickel-phosphorus plating|nickel-phosphorus]] or [[electroless nickel-boron plating|nickel-boron]] alloys for wear and corrosion resistance, [[Tollens' reagent#In silver mirroring|silver]] for [[mirror]]-making, [[copper]] for [[printed circuit board]]s, and many more.  A major advantage of these processes over electroplating is that they can produce coatings of uniform thickness over surfaces of arbitrary shape, even inside holes, and the substrate need not be electrically conducting.  Another major benefit is that they do not need power sources or specially-shaped anodes.  Disadvantages include lower deposition speed, consumption of relatively expensive chemicals, and a limited choice of coating metals.
* [[Immersion coating]] processes exploit [[displacement reaction]]s in which the substrate metal is oxidized to soluble ions while ions of the coating metal get reduced and deposited in its place.  This process is limited to very thin coatings, since the reaction stops after the substrate has been completely covered.  Nevertheless, it has some important applications, such as the [[electroless nickel immersion gold]] (ENIG) process used to obtain gold-plated electrical contacts on printed circuit boards.
* [[Sputtering]] uses an electron beam or a plasma to eject microscopic particles of the metal onto the substrate in a vacuum.
* [[Physical vapor deposition]] transfer the metal onto the substrate by evaporating it.
* [[Chemical vapor deposition]] uses a gas containing a volatile compound of the metal, which gets deposited onto the substrate as a result of a chemical reaction.
* [[Gilding]] is a traditional way to attach a gold layer onto metals by applying a very thin sheet of gold held in place by an [[adhesive]].
[[File:Luigi Valentino Brugnatelli. Stipple engraving by F. Bordiga Wellcome V0000839.jpg|thumb|upright|[[Luigi Valentino Brugnatelli]]]]

==History==
[[File:Moritz Hermann von Jacobi 1856.jpg|thumb|upright|[[Boris Jacobi]] developed electroplating, [[electrotyping]], and [[galvanoplastic sculpture]] in [[Russia]].]]In pre-Columbian South America, the [[Moche culture|Moche]] independently developed electroplating technology without any [[Old World]] influences. The Moche used electricity derived from chemicals to [[Gilding|gild]] copper with a thin layer of gold. In order to start the electroplating process, the Moche first concocted a very corrosive and a highly acidic liquid solution in which they dissolved small traces of gold. Copper inserted into the resulting acidic solution acted both as a [[cathode]] and an [[anode]], generating the electric current needed to start the electroplating process. The gold ions in the solution were attracted to the copper anode and cathode and formed a thin layer over the copper, giving the latter the appearance of a solid gold object, even though gold only coated the outermost layer of the copper object. The Moche then allowed the acidic solution to boil slowly, causing a very thin layer/coating of gold to permanently coat the copper anode and cathode. This battery-less electroplating technique was developed around 500 CE by the Moche, 1,300 years before Europeans invented the same process.<ref>{{Cite book| title= Encyclopedia of American Indian Contributions to the World: 15,000 Years of Inventions and Innovations | author =  Emory Dean Keoke, Kay Marie Porterfield | year = 2009 | page = 98 | publisher = Infobase | url= https://books.google.com/books?id=QIFTVWJH3doC&q=%5B%5BElectroplating%5D%5D+%E2%80%93+the+%5B%5BMoche+culture%7CMoche%5D%5D&pg=PA98 | isbn = 978-0816040520 }}</ref><ref>H. Lechtman, "A Pre-Columbian Technique for Electrochemical Plating of Gold and Silver on Copper Objects," Journal of Metals 31 (1979): 154–60</ref><ref>New perspectives on Moche Metallurgy: Techniques of Gilding Copper at Loma Negra, Northern Peru, Heather Lechtman, Antonieta Erlij, and Edward J. Barry [https://www.jstor.org/pss/280051 online abstract via ''www.jstor.org'']</ref>

Electroplating was independently invented in Europe by Italian chemist [[Luigi Valentino Brugnatelli]] in 1805. Brugnatelli used his colleague [[Alessandro Volta]]'s invention of five years earlier, the [[voltaic pile]], to facilitate the first electrodeposition. Brugnatelli's inventions were suppressed by the [[French Academy of Sciences]] and did not become used in general industry for the following thirty years. By 1839, scientists in [[United Kingdom|Britain]] and [[Russia]] had independently devised metal-deposition processes similar to Brugnatelli's for the copper electroplating of [[printing press]] plates.
[[File:Fragment of west barelief on St.Isaac cathedral.jpg|thumb|left|[[Galvanoplastic sculpture]] on [[St. Isaac's Cathedral]] in [[Saint Petersburg]]]]{{see also|Johann Wilhelm Ritter}}

Research from the 1930s had theorized that electroplating might have been performed in the [[Parthian Empire]] using a device resembling a [[Baghdad Battery]], but this has since been refuted; the items were fire-gilded using mercury.<ref>{{Cite web|date=2020-03-08|title=Debunking the So-Called "Baghdad Battery"|url=https://talesoftimesforgotten.com/2020/03/08/debunking-the-so-called-baghdad-battery/|access-date=2021-10-10|website=Tales of Times Forgotten|language=en-US}}</ref>

[[Boris Jacobi]] in Russia not only rediscovered galvanoplastics, but developed [[electrotyping]] and [[galvanoplastic sculpture]]. Galvanoplastics quickly came into fashion in Russia, with such people as inventor [[Peter Bagrationi|Peter Bagration]], scientist [[Heinrich Lenz]], and science-fiction author [[Vladimir Odoyevsky]] all contributing to further development of the technology.  Among the most notorious cases of electroplating usage in mid-19th century Russia were the gigantic galvanoplastic sculptures of [[St. Isaac's Cathedral]] in [[Saint Petersburg]] and gold-electroplated [[dome]] of the [[Cathedral of Christ the Saviour]] in [[Moscow]], the third [[List of tallest Orthodox churches| tallest Orthodox church in the world]].<ref name="galteh">{{cite web|url=http://www.galteh.ru/article_galvanotehnika.html|title=The history of galvanotechnology in Russia|url-status=dead|archive-url=https://web.archive.org/web/20120305183445/http://www.galteh.ru/article_galvanotehnika.html |archive-date=March 5, 2012 |language=ru}}</ref>

[[Image:Early Electro-Plating.jpg|thumb|left|Nickel plating]]

Soon after, [[John Wright (inventor)|John Wright]] of [[Birmingham]], England discovered that [[potassium cyanide]] was a suitable [[electrolyte]] for gold and silver electroplating.  Wright's associates, [[George Elkington]] and Henry Elkington were awarded the first patents for electroplating in 1840.  These two then founded the electroplating industry in [[Birmingham]] from where it spread around the world. The [[Woolrich Electrical Generator]] of 1844, now in [[Thinktank, Birmingham Science Museum]], is the earliest electrical generator used in industry.<ref>Birmingham Museums trust catalogue, accession number: 1889S00044</ref> It was used by [[Elkington Silver Electroplating Works|Elkingtons]].<ref name="thomas">{{cite book|last1=Thomas|first1=John Meurig|title=Michael Faraday and the Royal Institution: The Genius of Man and Place|date=1991|publisher=Hilger|location=Bristol|isbn=0750301457|page=51}}</ref><ref>{{cite book|last1=Beauchamp|first1=K. G.|title=Exhibiting Electricity|date=1997|publisher=IET|isbn=9780852968956|page=90}}</ref><ref>{{cite journal|last1=Hunt|first1=L. B.|title=The early history of gold plating|journal=Gold Bulletin|date=March 1973|volume=6|issue=1|pages=16–27|doi=10.1007/BF03215178|doi-access=free}}</ref>

The [[Norddeutsche Affinerie]] in [[Hamburg]] was the first modern electroplating plant starting its production in 1876.<ref>{{cite journal|doi = 10.1002/adem.200400403|title = Process Optimization in Copper Electrorefining|year = 2004|last1 = Stelter |first1=M.|journal = Advanced Engineering Materials|volume = 6|issue = 7|page=558|last2 = Bombach|first2 = H.| s2cid=138550311 }}</ref>

As the science of [[electrochemistry]] grew, its relationship to electroplating became understood and other types of non-decorative metal electroplating were developed. Commercial electroplating of [[nickel]], [[brass]], [[tin]], and [[zinc]] were developed by the 1850s. Electroplating baths and equipment based on the patents of the Elkingtons were scaled up to accommodate the plating of numerous large-scale objects and for specific manufacturing and engineering applications.

The plating industry received a big boost with the advent of the development of [[electric generator]]s in the late 19th century.  With the higher currents available, metal machine components, hardware, and [[automotive]] parts requiring corrosion protection and enhanced wear properties, along with better appearance, could be processed in bulk.

The two World Wars and the growing [[aviation]] industry gave impetus to further developments and refinements, including such processes as hard [[chromium plating]], [[bronze]] alloy plating, sulfamate nickel plating, and numerous other plating processes. Plating equipment evolved from manually-operated [[tar]]-lined wooden tanks to automated equipment capable of processing thousands of kilograms per hour of parts.

One of the American physicist [[Richard Feynman]]'s first projects was to develop technology for electroplating metal onto [[plastics|plastic]]. Feynman developed the original idea of his friend into a successful invention, allowing his employer (and friend) to keep commercial promises he had made but could not have fulfilled otherwise.<ref>{{cite book|first=Richard |last=Feynman |title=Surely You're Joking, Mr. Feynman! |date=1985 |chapter=Chapter 6: The Chief Research Chemist of the Metaplast Corporation|title-link=Surely You're Joking, Mr. Feynman! }}</ref>

== See also ==
* [[Anodizing]]
* [[Electrochemical engineering]]
* [[Electrogalvanization]]
* [[Electropolishing]]
* [[Nanolamination]]
* [[Electroforming]]
* [[Electrowinning]]

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==References==
{{Reflist}}

===Bibliography===
*{{cite book|last = Dufour|first = Jim|title = An Introduction to Metallurgy|edition = 5th|publisher = Cameron|year = 2006}}{{ISBN missing}}

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[[Category:Metal plating]]
[[Category:Italian inventions]]