What is Electroplating & How Does it Work
While electroplating may seem like advanced technology, it is actually a centuries-old process. The very first electroplating experiments occurred in the early 18th century , and the process was officially formalized by Brugnatelli in the first half of the 19th century. After Brugnatelli’s experiments, the electroplating process was adopted and developed across Europe. As manufacturing practices advanced over the next two centuries through the Industrial Revolution and two world wars, the electroplating process also evolved to keep up with demand, resulting in the process Sharretts Plating Company uses today.
Electroplating is also known as electrodeposition. As the name suggests, the process involves depositing material using an electric current. This process results in a thin layer of metal being deposited onto the surface of a workpiece called the substrate . Electroplating is primarily used to change the physical properties of an object. This process can be used to give objects increased wear resistance, corrosion protection or aesthetic appeal, as well as increased thickness.
Electroplating is a popular metal finishing and improving process used in a wide range of industries for various applications. Despite the popularity of electroplating, however, very few outside of the industry are familiar with the process, what it is and how it works. If you’re considering using electroplating in your next manufacturing process, you need to know how the process works and what material and process options are available to you.
ELECTROPLATING PROCESS
The electroplating process uses an electric current to dissolve metal and deposit it onto a surface. The process works using four primary components:
Anode: The anode, or positively charged electrode, in the circuit is the metal that will form the plating.
Cathode: The cathode in the electroplating circuit is the part that needs to be plated. It is also called the substrate. This part acts as the negatively charged electrode in the circuit.
Solution: The electrodepositing reaction takes place in an electrolytic solution. This solution contains one or more metal salts, usually including copper sulfate, to facilitate the flow of electricity.
Power source: Current is added to the circuit using a power source. This power source applies a current to the anode, introducing electricity to the system.
Once the anode and cathode are placed in solution and connected, the power supply supplies a direct current (DC) to the anode. This current causes the metal to oxidize, allowing metal atoms to dissolve in the electrolyte solution as positive ions. The current then causes the metal ions to move to the negatively charged substrate and deposit onto the piece in a thin layer of metal.
As an example, consider the process of plating gold onto metal jewelry. The gold plating metal is the anode in the circuit, while the metal jewelry is the cathode. Both are placed in solution and DC power is supplied to the gold, which dissolves in solution. The dissolved gold atoms then adhere to the surface of the base metal jewelry, creating a gold coating.
While this process is constant, three factors can impact the quality of the plating. These factors are the following:
Bath conditions: Both the temperature and the chemical composition of the bath impact how effective the electroplating process is.
Part placement: The distance the dissolved metal needs to travel will affect how effectively the substrate is plated, so the placement of the anode relative to the cathode is important.
Electrical current: Both the voltage level and the application time of the electrical current plays a role in the efficacy of the electroplating process.
WHICH METALS ARE USED IN THE ELECTROPLATING PROCESS?
Plating can occur with individual metals or in various combinations (alloys) that can provide additional value to the electroplating process. Some of the most commonly used metals for electroplating include:
Copper: Copper is often used for its conductivity and heat resistance. It is also commonly used to improve adhesion between layers of material.
Zinc: Zinc is highly corrosion-resistant. Often, zinc is alloyed with other metals to enhance this property. For example, when alloyed with nickel, zinc is particularly resistant to atmospheric corrosion.
Tin: This matte, bright metal is highly solderable and corrosion resistant as well as environmentally friendly. It is also inexpensive compared to other metals.
Nickel: Nickel offers excellent wear resistance, which can be improved through heat treatment. Its alloys are also very valuable, offering elemental resistance, hardness and conductivity. Electroless nickel plating is also valued for its corrosion resistance, magnetism, low friction and hardness.
Gold: This precious metal offers high corrosion, tarnish and wear resistance and is coveted for its conductivity and aesthetic appeal.
Silver: Silver is not as corrosion resistant as gold, but it is highly ductile and malleable, has excellent resistance to contact wear and offers excellent aesthetics. It is also an alternative to gold in applications where thermal and electrical conductivity is needed.
Palladium: This bright metal is often used instead of gold or platinum for its hardness, corrosion resistance and beautiful finish. When alloyed with nickel, this metal achieves excellent hardness and plating quality.
Price, substrate composition and desired result are key factors when determining the most appropriate electroplating material for your application.
There are several different plating techniques available, each of which can be used in various applications. Some of these types of electroplating are described in more detail below:
Barrel plating: Barrel plating is a method used to plate large groups of small parts. In this process, parts are placed inside a barrel filled with an electrolyte solution. The electroplating process proceeds while the barrel is rotated, agitating the parts so that they receive consistently even finishes. Barrel plating is best used on small, durable parts, but offers a cheap, efficient and flexible solution.
Rack electroplating: Rack or wiring plating is a good option if you need to plate large groups of parts. In this method, parts are placed on a wire rack, allowing each part to come into physical contact with the electrical power source. Though more expensive, this option is optimal for more delicate parts that cannot undergo barrel plating. It is important to note that rack plating is more difficult for parts that are sensitive to electricity or have an irregular shape.
Electroless plating: Electroless plating, also known as autocatalytic plating, uses a similar process as electrodeposition but does not directly apply electricity to the part. Instead, the plating metal is dissolved and deposited using a chemical reaction in place of an electrical one. While this option is useful for parts that are incompatible with electrical currents, it is more costly and less productive than other options.
While these methods accomplish electrodeposition in different ways, they all use the same basic principles.
USES OF ELECTROPLATING
While electroplating is often used to improve the aesthetic appearance of a base material, this technique is used for several other purposes across multiple industries. These uses include the following:
Build thickness: Electroplating is often used to build up the thickness of a substrate through the progressive use of thin layers.
Protect substrate: Electroplated layers serve as sacrificial metal coatings. This means that when a part is placed in a harmful environment, the plated layer breaks down before the base material, protecting the substrate from damage.
Lend surface properties: Electroplating allows substrates to benefit from the properties of the metals they are plated with. For example, some metals protect against corrosion, improve electrical conductivity, reduce friction or prepare a surface for better paint adhesion. Different metals lend different properties.
Improve appearance: Of course, electroplating is also commonly used to improve the aesthetic appearance of a substrate. This can mean plating the substrate with an aesthetically pleasing metal or simply applying a layer to improve surface uniformity and quality.
BENEFITS OF ELECTROPLATING
Electroplating offers a range of benefits for components. Some of the specific benefits of electroplating include the following:
Protective barrier: Electroplating creates a barrier on the substrate, protecting it against environmental conditions. In some cases, this barrier can protect against corrosion caused by the atmosphere. This property specifically benefits components because the parts last longer in more harsh conditions, meaning that they need less frequent replacement.
Enhanced appearance: Exterior pieces are often plated with thin layers of precious metals to make them more lustrous and attractive to look at. This plating lends aesthetic appeal without exorbitant costs, meaning that attractive parts can be sold at lower prices. Additionally, electroplating is often used to prevent tarnishing on silverware, improving longevity and aesthetic appearance over time.
Electrical conductivity: Silver and copper plating help improve electrical conductivity in parts, offering a cost-effective, efficient solution for improving conductivity in electronics and electrical components.
Heat resistance: Several metals, including gold and zinc-nickel, are resistant to high temperatures, improving the ability of the substrate to resist heat damage. This, in turn, can improve the lifespan of plated parts.
Improved hardness: Electroplating is often used to improve the strength and durability of substrate materials, making them less susceptible to damage from stress or rough use. This quality can help increase the lifespan of plated parts, reducing the need for replacement.
Some benefits offered are metal-specific. For example, nickel plating is useful for reducing friction, which helps to reduce wear and tear and improve part longevity. Zinc-nickel alloys, on the other hand, are used to prevent the formation of sharp protrusions during manufacturing, which can result in part damage. Copper is also specifically used as an undercoating in many applications, as it facilitates adhesion with additional metal coatings to improve the surface quality of the final part.
INDUSTRIES THAT USE ELECTROPLATING
Whether your company is looking for corrosion protection, improved durability or increased electrical conductivity, electroplating offers solutions. That’s why electroplating is widely used across a variety of industries.
Automotive industry: Plating is commonly used in the automotive industry to prevent corrosion in harsh environmental conditions. Zinc-nickel plating solutions help prevent rust formation, while electroless nickel plating serves as a great alternative for chrome on catalytic converters and plastic parts.
Electronics industry: Electronics companies often use gold plating for its conductivity, applying it to semiconductors and connectors. Gold is also coveted for its corrosion resistance in this industry. Copper plating is another commonly used metal in this industry, used as an alternative to gold when the focus is on conductivity. Palladium alloys are also commonly used as protective coatings on electronic equipment and components.
Medical industry: The medical equipment industry often uses metal electroplating to improve the biocompatibility of components, especially implants. Gold, silver and titanium are commonly used in this industry for their biocompatibility, corrosion resistance, hardness and wear resistance, all of which are essential for implants and joint replacements.
Aerospace industry: The aerospace industry frequently uses titanium for aircraft manufacturing due to its high strength-to-weight ratio. Nickel plating is also commonly used in this industry to protect against corrosion and wear, while copper is used to improve heat resistance.
Oil and gas industry: Corrosion protection is a primary concern of the oil and gas industry due to the nature of petrochemicals. Electroless nickel plating is often used in this industry to help protect piping and other components from corrosion, which helps improve the longevity of parts.
Many other industries, including the firearms, military and defense industries, also use electroplating in various applications. All of these industries favor electroplating for its functional capabilities, as well as its low cost and flexibility of application.
ELECTROPLATING EXAMPLES
There are many specific examples of electroplating applications across various industries. Some of these are detailed below:
Copper plating of semiconductors: Various metal plating options are used in the electronics industry. Copper plating is commonly used to increase the ability of semiconductors and circuits to conduct electricity.
Nickel plating of hard drives: Nickel is a magnetic metal, which is an essential property for hard drives. Hard drives require magnetism to improve disc reading, so hard drives are commonly electroplated with nickel during the manufacturing process.
Palladium plating of catalytic converters: Palladium plating is commonly used in the automotive industry, specifically on catalytic converters. Palladium absorbs excess hydrogen during the manufacturing process, an element that negatively impacts the functionality of catalytic converters. Plating with palladium absorbs this excess hydrogen, improving catalytic converter performance.
Electroless nickel plating of aerospace components: Black electroless nickel plating is capable of absorbing light and energy. This is an essential quality in the manufacturing of various types of defense vehicles. Many defense and aerospace industry manufacturers choose to use this plating option to ensure compliance with industry standards, including the Department of Defense guidelines.
How electroplating works
Electroplating
There's no such thing as alchemy—magically changing common chemical elements into rare and valuable ones—but electroplating is possibly the next best thing. The idea is to use electricity to coat a relatively mundane metal, such as copper, with a thin layer of another, more precious metal, such as gold or silver. Electroplating has lots of other uses, besides making cheap metals look expensive. We can use it to make things rust-resistant, for example, to produce a variety of useful alloys like brass and bronze, and even to make plastic look like metal. How does this amazing process work? Let's take a closer look!
Photo: Electroplating in action—an exhibit at Think Tank (the science museum in Birmingham, England). These two forks are the electrodes and the blue solution (copper sulfate) is being used to copper-plate one of them.
What is electroplating?
Photo: Gold-plated: When astronaut Ed White made the first American spacewalk in 1965, he was wearing a gold-plated visor on his helmet to protect his eyes from solar radiation. Photo by courtesy of NASA on the Commons.
Electroplating involves passing an electric current through a solution called an electrolyte. This is done by dipping two terminals called electrodes into the electrolyte and connecting them into a circuit with a battery or other power supply. The electrodes and electrolyte are made from carefully chosen elements or compounds. When the electricity flows through the circuit they make, the electrolyte splits up and some of the metal atoms it contains are deposited in a thin layer on top of one of the electrodes—it becomes electroplated. All kinds of metals can be plated in this way, including gold, silver, tin, zinc, copper, cadmium, chromium, nickel, platinum, and lead.
Electroplating is very similar to electrolysis (using electricity to split up a chemical solution), which is the reverse of the process by which batteries produce electric currents. All these things are examples of electrochemistry: chemical reactions caused by or producing electricity that give scientifically or industrially useful end-products.
How does electroplating work?
First, you have to choose the right electrodes and electrolyte by figuring out the chemical reaction or reactions you want to happen when the electric current is switched on. The metal atoms that plate your object come from out of the electrolyte, so if you want to copper plate something you need an electrolyte made from a solution of a copper salt, while for gold plating you need a gold-based electrolyte—and so on.
Next, you have to ensure the electrode you want to plate is completely clean. Otherwise, when metal atoms from the electrolyte are deposited onto it, they won't form a good bond and they may simply rub off again. Generally, cleaning is done by dipping the electrode into a strong acid or alkaline solution or by (briefly) connecting the electroplating circuit in reverse. If the electrode is really clean, atoms from the plating metal bond to it effectively by joining very strongly onto the outside edges of its crystalline structure.
Now we're ready for the main part of electroplating. We need two electrodes made from different conducting materials, an electrolyte, and an electricity supply. Generally, one of the electrodes is made from the metal we're trying to plate and the electrolyte is a solution of a salt of the same metal. So, for example, if we're copper plating some brass, we need a copper electrode, a brass electrode, and a solution of a copper-based compound such as copper sulfate solution. Metals such as gold and silver don't easily dissolve so have to be made into solutions using strong and dangerously unpleasant cyanide-based chemicals. The electrode that will be plated is generally made from a cheaper metal or a nonmetal coated with a conducting material such as graphite. Either way, it has to conduct electricity or no electric current will flow and no plating will occur.
Artwork: Copper-plating brass: You need a copper electrode (gray, left), a brass electrode (yellow, right), and some copper sulfate solution (blue). The brass electrode becomes negatively charged and attracts positively charged copper ions from the solution, which cling to it and form an outer coating of copper plate.
We dip the two electrodes into the solution and connect them up into a circuit so the copper becomes the positive electrode (or anode) and the brass becomes the negative electrode (or cathode). When we switch on the power, the copper sulfate solution splits into ions (atoms with too few or too many electrons). Copper ions (which are positively charged) are attracted to the negatively charged brass electrode and slowly deposit on it—producing a thin later of copper plate. Meanwhile, sulfate ions (which are negatively charged) arrive at the positively charged copper anode, releasing electrons that move through the battery toward the negative, brass electrode.
It takes time for electroplated atoms to build up on the surface of the negative electrode. How long exactly depends on the strength of the electric current you use and the concentration of the electrolyte. Increasing either of these increases the speed at which ions and electrons move through the circuit and the speed of the plating process. As long as ions and electrons keep moving, current keeps flowing and the plating process continues.
Electroplating
Electroplating is the process of plating one metal onto another by hydrolysis, most commonly for decorative purposes or to prevent corrosion of a metal. There are also specific types of electroplating such as copper plating, silver plating, and chromium plating. Electroplating allows manufacturers to use inexpensive metals such as steel or zinc for the majority of the product and then apply different metals on the outside to account for appearance, protection, and other properties desired for the product. The surface can be a metal or even plastic.
Introduction
Sometimes finishes are solely decorative such as the products we use indoors or in a dry environment where they are unlikely to suffer from corrosion. These types of products normally have a thin layer of gold, or silver applied so that it has an attractive appeal to the consumer. Electroplating is widely used in industries such as automobile, airplanes, electronics, jewelry, and toys. The overall process of electroplating uses an electrolytic cell, which consists of putting a negative charge on the metal and dipping it into a solution that contains metal salt (electrolytes) which contain positively charged metal ions. Then, due to the negative and positive charges, the two metals are attracted to each other.
The Purposes of Electroplating:
Appearance
Protection
Special surface properties
Engineering or mechanical properties
Background
The cathode would be the piece to be plated and the anode would be either a sacrificial anode or an inert anode, normally either platinum or carbon (graphite form). Sometimes plating occurs on racks or barrels for efficiency when plating many products. Please refer to electrolysis for more information. In the figure below, the Ag+ ions are being drawn to the surface of the spoon and it eventually becomes plated. The process is undergone using silver as the anode, and a screw as the cathode. The electrons are transferred from the anode to the cathode and is underwent in a solution containing silver.
History of Electroplating
Electroplating was first discovered by Luigi Brugnatelli in 1805 through using the electrodeposition process for the electroplating of gold. However his discovery was not noted as he was disregarded by the French Academy of Science as well as Napolean Bonaparte. But a couple of decades later, John Wright managed to use potassium cyanide as an electrolyte for gold and silver. He discovered that potassium cyanide was in fact an efficient electrolyte. The Elkington cousins later in 1840 used potassium cyanide as their electrolyte and managed to create a feasible electroplating method for gold and silver. They attained a patent for electroplating and this method became widely spread throughout the world from England. Electroplating method has gradually become more efficient and advanced through the use of more eco-friendly formulas and by using direct current power supplies.
Choosing the Electrolytes
There are many different metals that can be used in plating and so determining the right electrolyte is important for the quality of plating. Some electrolytes are acids, bases, metal salts or molten salts. When choosing the type of electrolyte some things to keep in mind are corrosion, resistance, brightness or reflectivity, hardness, mechanical strength, ductility, and wear resistance.
Preparing the Surface
The purpose of preparing the surface before beginning to plate another metal onto it is to ensure that it is clean and free of contaminants, which may interfere with the bonding. Contamination often prevents deposition and lack of adhesion. Normally this is done in three steps: cleaning, treatment and rinsing. Cleaning usually consists of using certain solvents such as alkaline cleaners, water, or acid cleaners in order to remove layers of oil on the surface. Treatment includes surface modification which is the hardening of the parts and applying metal layers. Rinsing leads to the final product and is the final touch to electroplating.Two certain methods of preparing the surface are physical cleaning and chemical cleaning. Chemical cleaning consists of using solvents that are either surface-active chemicals or chemicals which react with the metal/surface. In physical cleaning there is mechanical energy being applied in order to remove contaminants. Physical cleaning includes brush abrasion and ultrasonic agitation.
Types of Electroplating
There are different processes by which people can electroplate metals such as by mass plating (also barrel plating), rack plating, continuous plating, and line plating. Each process has its own set of procedures which allow for the ideal plating.
Table 1: Electroplating methods Mass Plating It's not ideal for items that are detailed as it is not effective in preventing scratches and entanglement. However, this process plates a mass amount of objects efficiently. Rack Plating More expensive than mass plating, but effective for either large or delicate parts. Often has parts submerged in solutions with "racks". Continuous Plating Parts such as wires and tubes are continuously passing anodes at a certain rate. This process is a bit cheaper. Line Plating Cheaper, as fewer chemicals are used and a production line is used to plate parts.
The Plating Metals
Most electroplating coatings can be separated into these categories:
Sacrificial Coating Decorative Coating Functional Coatings Minor Metals Unusual metal Coating Alloy Coatings is used primarily for protection. The metal used for the coating is sacrificial, being used up, in the reaction. Common metals include: zinc and cadmium (now forbidden in many countries). is used primarily for appeal and attractive purposes. Common metals include: copper, nickel, chromium, zinc and tin. are coatings done based on necessity and functionality of the metal. Common metals include: gold, silver, platinum, tin, lead ruthenium, rhodium, palladium, osmium, and iridium. are normally iron, cobalt, and indium because they are easy to plate, but are rarely used in plating. are metals that are even more rarely used for plating than the minor metals. These include: As, Sb, Bi, Mn, Re, Al, Zr, Ti, Hf, V, Nb, Ta, W, and Mo. An alloy is a substance that has metallic properties and is made up of two or more elements. These coatings are made by plating two metals in the same cell. Common combinations include: gold–copper–cadmium, zinc–cobalt, zinc–iron, zinc–nickel, brass (an alloy of copper and zinc), bronze (copper–tin), tin–zinc, tin–nickel, and tin–cobalt.
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