Electroplating Explained - How It Works, Types, Benefits & ...
Electroplating Explained - How It Works, Types, Benefits & ...
Electroplating is a common surface finishing process in the manufacturing industry to coat a material (substrate) with another metal. In recent years, the process has undergone many advances, making it much more accurate and capable of working with a wider range of materials.
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In this article, we will explore the modern electroplating process to understand what it is, how it works, its benefits and limitations.
What Is Electroplating?
Electroplating is a manufacturing process in which a thin layer of metal atoms is deposited to another material through electrolysis. The metal added is known as the deposition metal, and the underlying material or workpiece is known as the substrate material.
By adding a layer of the desired metal, we can improve several physical, mechanical and chemical properties of the substrate, such as its strength, heat conductivity, electrical conductivity, abrasion and corrosion resistance.
Improving these properties can allow us to combine different metals to achieve properties that perfectly suit different applications.
How Does the Electroplating Process Work?
The electroplating process works on the principle of the electrolytic cell.
In this process, two metal rods are placed in an electrolyte. The rods act as electrodes when connected to the opposite terminals of a battery or power supply to create a potential difference. The electric current causes the electrolyte bath to disintegrate into dissolved metal ions, and the positively charged metal ions deposit on the negative electrode (cathode).
These positively charged ions are part of the electrolyte. As they get deposited on the cathode, their concentration in the electrolyte reduces. By choosing a suitable element for the anode, we can replenish the concentration of the positive ions.
For instance, if we need to coat brass with copper, the brass becomes the substrate. Connecting it to the negative terminal makes it the cathode. We use an electrolyte, such as a copper sulfate solution, that gives positive copper ions upon disintegrating. On the other end, we use a copper anode to replenish the electrolyte&#;s positive ions.
We can control the plate thickness, rate of metal deposition, surface finish, colour and many other factors by manipulating the process parameters. For example, using pure copper plates will give a better appearance than regular copper rods available in the market.
Using this process, the material can be coated with one or more metals.
Types of Electroplating Methods
Over the years, the electroplating process setup has evolved to suit different applications. By choosing a method in line with the application, the efficiency of the operation can be increased significantly.
To choose the right one, we must first understand the different types. Overall, electroplating methods can be divided into four major types. These are:
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Mass plating
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Rack plating
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Continuous plating
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In-line plating
Mass Plating
Barrel plating
As the name suggests, mass plating is used for mass-production applications. The method can handle a large volume of products that require thin coatings of metal.
A common type of mass plating method is known as barrel plating. In this method, the material to be coated (substrate) is dipped in a barrel containing the metal salt (electrolyte) and the anode of the coating metal.
The barrel plating setup is highly economical for small parts that need a uniform coating. As the barrel rotates, all the parts are cleaned, descaled and uniformly coated to a greater extent compared to rack plating.
This method is not recommended for parts that require a detailed finish without scratches and entanglement.
Mass plating is generally used for small but robust parts such as nuts, bolts and screws.
Rack plating
Rack plating
When the parts are larger than those suitable for mass plating, the rack plating method is used. In rack plating, the parts are mounted on racks and immersed in the chemical electroplating bath.
The rack plating process reduces the damage to delicate or fragile parts and coats the interior contours and deep crevices of parts, unlike mass plating.
This process is, however, more expensive than mass plating. But it makes up for it by providing a plated layer of much higher quality than a mass-plated product.
Rack plating is typically best for large, fragile and complex parts that require a plating of gold, silver, tin, copper or nickel.
Continuous plating
The continuous plating process is performed on exceptionally long parts, such as metal tubes, wires and strips.
In the case of thin strips, this process is also known as the reel-to-reel plating process. In this process, a long product is passed through the chemical bath at a specified rate. The end product&#;s quality is controlled by manipulating the process parameters and the time spent in the bath.
The reel of the product to be coated is uncoiled at the initial station, and once it passes the electrolyte/anode and gets coated, it is recoiled for easier storage and transport. Then further operations can be performed to stamp it into the required shapes.
In-line plating
The in-line plating method uses an assembly line for the metal plating operation. The metal passes through the various stations and automated machinery facilitates the chemical reaction.
Line plating is generally used for coating copper, zinc, chromium and cadmium. A variety of substrates can be coated with these metals through line plating. This method is relatively cheaper than other methods because a lower amount of chemicals is needed per piece.
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Suitable Materials
Electroplating is a versatile process owing to the fact that it requires only one property in the substrate: electrical conductivity.
Since this property is exclusively available with metals (barring a few exceptions), we could initially use electroplating only for metals. But with the advent of conductive sprays and coatings, it is now possible to coat non-conducting materials such as plastic and wood too.
As a result, today, there are many more materials that can be electroplated. The substrate material can greatly vary depending on the application.
Silver or gold plating is often used to improve the appearance. To improve properties such as bacterial resistance and conductivity, copper plating is a favourite. Copper electroplating also offers increased malleability, lubricity and corrosion resistance.
Similarly, when we need to improve corrosion and wear resistance simultaneously, we go for nickel plating. Nickel also improves the appearance of the product.
Some other metals that are normally used for coating in electroplating are chromium, cadmium, zinc, iron and titanium.
But the substrate and the coating must be chosen carefully. Not all materials combine with each other. For example, steel cannot be plated with silver right away. It must first be plated with copper or nickel before silver plating.
Benefits
The first modern electroplating plant was set up in Hamburg in the late 19th century. The intention was to improve the appearance. But as science understood the mechanism and benefits of electroplating, its applications for non-decorative purposes became common.
Today, we understand the true breadth of electroplating benefits. Let&#;s list them down for a better overall understanding.
Improved physical properties (colour, lustre, conductivity, low weight)
Electroplating improves physical properties such as colour, lustre and conductivity.
Colour and lustre provide cosmetic upgrades that are necessary for many day-to-day products as well as art applications.
Everyday appliances and kitchen products such as utensils, pans, cutlery, taps, kettles and other gadgets become much more attractive when coated with shinier metals such as copper, gold or silver. It also improves their functionality, as electroplated products are often easier to clean.
The appearance of artistic installations such as sculptures and figurines can also be improved by using electroplating. As a result, electroplating also finds use in art restoration and preservation projects besides new art creation.
Functionality can also receive a boost in technical applications involving electrical components such as antennas and integrated circuits. Although metals are already conductive, coating them with a better conductor improves the overall conductivity of the part while keeping costs low.
Costs are also reduced by the fact that non-metals can be used for electrical applications after electroplating. Besides having lower costs, non-metals also weigh less, which reduces the cost and difficulty related to the transport and storage of products.
Improved mechanical properties (tensile strength, bending strength, abrasion resistance, surface finish)
Electroplating also improves mechanical properties such as tensile strength, wear resistance and durability, depending on the application.
The small increase in tensile strength is enough to bridge the gap between the SLA resins of 3D printing (plastics) and metal alloys. The distinct strength characteristics allow the use of electroplated materials in applications where previously metals would have had to be used.
The metal skin on a plastic product, besides making the product lighter, also imparts excellent flexural strength characteristics.
We can also improve the surface finish using electroplating. This makes the products easier to handle and reduces friction.
All these improvements increase the short-term performance while also lengthening the lifespan of the products.
Improved Chemical Properties (Corrosion, Chemical, UV and Radiation Resistance)
The chemical properties of a material can also be enhanced by using electroplating. Properties such as corrosion resistance, resistance to chemicals and UV light are crucial in certain applications such as medical implants.
Typically, medical implants depend on precious metal coatings of gold, silver, platinum and copper for their corrosion protection, electrical conductivity, heat dissipation, non-toxic and antibacterial nature.
Chemical and corrosion-resistant products are also required for harsh service environments where the product is exposed to chemicals, moisture and seawater.
Limitations
Electroplating has certain disadvantages that prevent its use in some cases. Let&#;s evaluate these to get a complete picture.
Complex process
The process is far from simple and can be difficult to carry out reliably. A process would have to be set with predetermined parameters to obtain parts of a consistent quality. Mistakes in preparation and pretreatment can lead to defects, poor quality and capability of finished parts.
Electroplating cannot be used for all material combinations, as they may not combine well with the plating solution.
Long plating time
The plating time can be excessively long in some cases. The metal deposition rate can be increased by either increasing the power supply or the concentration of the electrolyte or both. But this will cause uneven deposition, which can be a dealbreaker in some cases.
The benefits are limited to the surface
By its nature, electroplating is only limited to the surface. Once the surface layer is scratched off, the product can lose some or all of the benefits provided by the process.
Hazardous nature
The process releases gases due to the reduction at the cathode. If these gases are of a hazardous nature, they pose considerable risks for personnel in the vicinity.
Hexavalent chromium exposure from chrome plating is an apt example of how hazardous the electroplating process can be.
Wrapping It Up
Electroplating is nothing short of an engineering wonder. In the past, we could only use it on metals, but that is no longer the case. Today, we can electroplate plastics, ceramics and even organic materials such as leaves and flowers.
However, it still remains a very difficult process to execute consistently. This is why engineers and designers should turn to electroplating service providers for their expertise. Fractory&#;s sales engineers have plenty of experience in planning and executing custom projects, so don&#;t hesitate to get in touch.
FAQ
How do I identify the positive and negative terminals of the power supply in the electroplating solution?
It is very important to maintain the right polarity during electroplating. If for some reason you are not able to identify the anode (positive electrode) from the cathode (negative electrode), remember that the bubbles are generated on the cathode during the reaction.
This tells us that the electrode with the bubble formation is connected to the negative terminal of the power supply.
What is the difference between electroplating and electropolishing?
Electropolishing is basically the reverse operation of plating. Instead of adding material, electrochemical polishing removes it. In the electropolishing process, the workpiece is the anode, contrary to electroplating, where the workpiece is the cathode. Thus, electropolishing is also known as the reverse plating process.
What is electroless plating?
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Electroless plating works on the principle of an electrochemical cell. A chemical reaction causes the deposition of one material on another without the need for an electric current. The coating metal is usually a metal or a metal alloy and the substrate could be either a metal or non-metal such as plastic, ceramic, glass, etc.
What is electroforming?
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The electroforming process refers to the use of electric current across a chemical bath to form solid models with intricate cavities. The process is similar to electroplating except that instead of a surface, we are building a solid article with a complex cavity.
It uses a template known as the mandrel. The mandrel is dipped in the electrolyte and the electrolytic reaction forms a layer of the deposition metal on the mandrel in the negative shape of the mandrel.
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 coated acts as the cathode (negative electrode) of an electrolytic cell; the electrolyte is a solution of a 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 conductive material. The current is provided by an external power supply.
Electroplating is widely used in industry and decorative arts to improve the surface qualities of objects&#;such as resistance to abrasion and corrosion, 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/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.[1]
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.[2] A higher throwing power of the plating bath results in a more uniform coating.[3]
Process
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Simplified diagram for electroplating copper (orange) on a conductive object (the cathode, "Me", gray). The electrolyte is a solution of copper sulfate,CuSO
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Cu
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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 Cu2+ cations and SO2&#;
4 anions. At the cathode, the Cu2+ 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 Cu2+ 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.
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.[5]
The plating is most commonly a single metallic 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 cyanides 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 carbonates and phosphates 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, lacquers, and waxes.[6]
Strike
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Initially, a special plating deposit called a strike or flash may be used to form a very thin (typically less than 0.1 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.[5]
Pulse electroplating
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The pulse electroplating or pulse electrodeposition (PED) process involves the swift alternating of the electrical potential or 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.[7]
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 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
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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 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
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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.[8]
Cleanliness
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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. Surfactants such as soap reduce the sensitivity of the test and must be thoroughly rinsed off.
Test cells and characterization
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Throwing power
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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.[2] Micro throwing power refers to the extent to which a process can fill or coat small recesses such as through-holes.[9] Throwing power can be characterized by the dimensionless Wagner number:
Wa = R T κ F L α | i | , {\displaystyle {\text{Wa}}={\frac {RT\kappa }{FL\alpha |i|}},}
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 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 |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 |i|; however, this effect can be offset by blockage due to hydrogen bubbles and hydroxide deposits.[10]
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 M = m1 / m2 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 L = x2 / x1 of the distances of these regions through the electrolyte to the anode. In a Haring-Blum cell, for example, L = 5 for its two independent cathodes, and a cell yielding plating thickness ratio of M = 6 has Harring-Blum throwing power 100% × (L &#; M) / L = &#;20%.[9] Other conventions include the Heatley throwing power 100% × (L &#; M) / (L &#; 1), and Field throwing power 100% × (L &#; M) / (L + M &#; 2).[11] A more uniform thickness is obtained by making the throwing power larger (less negative) 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.[9]
Haring&#;Blum cell[
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Haring&#;Blum cellThe 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.[12][13]
Hull cell
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A zinc solution tested in a Hull cellThe 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.[14] 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 gram addition to 267 mL is equivalent to 0.5 oz/gal in the plating tank.[15]
Effects
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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.[16] 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
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Alternatives to electroplating
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There are a number of alternative processes to produce metallic coatings on solid substrates that do not involve electrolytic reduction:
- Electroless deposition uses a bath containing metal ions and chemicals that will reduce them to the metal by redox reactions. The reaction should be 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 nickel-phosphorus or nickel-boron alloys for wear and corrosion resistance, silver for mirror-making, copper for printed circuit boards, 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 reactions 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.
History
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Electroplating was invented by Italian chemist Luigi Valentino Brugnatelli in . 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 , scientists in Britain and Russia had independently devised metal-deposition processes similar to Brugnatelli's for the copper electroplating of printing press plates.
Research from the s 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.[17]
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 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 tallest Orthodox church in the world.[18]
Nickel platingSoon after, 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 . These two then founded the electroplating industry in Birmingham from where it spread around the world. The Woolrich Electrical Generator of , now in Thinktank, Birmingham Science Museum, is the earliest electrical generator used in industry.[19] It was used by Elkingtons.[20][21][22]
The Norddeutsche Affinerie in Hamburg was the first modern electroplating plant starting its production in .[23]
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 s. 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 generators 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 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.[24]
See also
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References
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Bibliography
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- Dufour, Jim (). An Introduction to Metallurgy (5th ed.). Cameron.[
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