Electroplating

Metals maybe electroplated for aesthetics protection or both. Aesthetics might involve making a metal shinier or giving it an attractive color by coating. For example, jewelry is often plated gold or silver. A metal coating can be used for protection as it may help resist corrosion rusting or just general wear and tear. Car rims are electroplated for both shininess and protection. Chromium commonly known as chrome, nickel, tin, zinc and cadmium are often used to play copper iron and steel objects.

An electric current is passed through a solution that conducts electricity, could an electrolyte to create this current. Two electrodes dipped into the electrolyte solution and connected to a battery or power supply. When the current is turned on, the electrodes gain a charge. The positively charged electrode is called the anode and the negatively charged electrode is called the cathode. The electrodes and electrolyte are carefully chosen based upon what metal you are plating with. If you want to copy plate another metal, you will use a copper based electrolyte solution and have a copper anode. The copper for the plating comes from the electrolyte solution which in turn has it stops replenished by the copper anode.

Look at copper plating as an example, we want to copy place and brass, so we have a copper anode, a brass cathode and a copper based solution for the electrolyte. Copper sulfate solution contains blue copper ions and colorless sulfate ions. The copper ions are positively charged and so attracted to the negatively charged brass cathode. The copper ions deposit onto the brass, producing the thin copper plate. The positively charged copper ions gain electrons, which is known as reduction. The sulfate ions are negatively charged and so are attracted to the positively charged copper anode. The current supplied to the anode causes the copper atoms to oxidize, which is lost electrons and then dissolve into the electrolyte solution. The copper ions move from the anode to the cathode in the solution, and the electrons move from the anode to the cathode but along the wire. The copper anode bug gradually dissolves to replenish the copper ions in the electrolyte solution. The solution stays at the same concentration if another matter was used at the anode, then the copper sulfate solution would get paler or less concentrated. Oxidation the loss of electrons takes place at the anode and reduction the gain of electrons take place at the cathode.

Types of Electroplating Methods

 

1.Mass 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.

2.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.

 

3.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.

4.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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