Metal finishing process is a topic that can’t be left untreated as almost everything around us are made of some types of metal or contains metal part on them. metal has play a key role in our lives for thousands of years till date and its benefits have effect in every technological innovation. Life would have been very hard and boring without metals, starting from automobiles, jewelry, planes, doors, windows, bolts and nuts etc. are made with metals.
Due to the fact that metals are used to produce decorative items, the final appearance must be appealing. In some situation where the final appearance of item made of metal is considered finishing process must be perform. In addition to metal finishing process, it plays an important role in adding to the property of a metal, covering the surface with a thin layer.
Today we’ll be looking at the definition, considerations, types, applications as well as the advantages of metal finishing process.
Contents
What is metal finishing process?
Metal finishing process is the process of placing or applying some type of metal coating on the surface of a metallic part. It is used to treat the exterior of metal products by applying a thin complementary layer to its surface. Metal finishing can also be said to be the implementation of a process for cleaning, polishing or enhancing metal surfaces.
Read: Different types of sheet metal forming processes
Things to Consider before choosing a Metal Finishing Process
There are few things to be consider when selecting metal finishing techniques for your project. The following stated below are the factors:
- Production speed: how fast will the finishing technique be performed.
- Cost-effectiveness: some finishing machine like vibratory tumblers are very expensive but will offers faster cycle rates.
- Potential for vulcanization is also one factor to be considered.
- Metal properties: if the material is hard metals an intense finishing method like grinding maybe required.
Various types of metal finishing processes
The following stated below represent the various techniques of metal finishing:
Electroplating:
This metal finishing process is also known as electrodeposition, which is achieve by depositing metal or metal alloy onto the surface of a substrate. An electric current is passed through a liquid that contains dissolved ion and the substrate. This object serves as a cathode and attracts the metal ions in the plating bath. A pretreatment process such as cleaning, rinsing and stripping is performed be the electroplating process.
Electroless Plating:
The electroless plating is similar to the electroplating finishing method in that the substrate is placed in liquid solution containing the desired metal, often copper or nickel. Their major difference is the way in which the deposition occurs; the metal coating is applied via chemical reaction instead of electricity. The plating bath normally includes a complexing agent to maintain the metal solution and various which helps to maintain stability. It also increases the bath life.
Vibratory Finishing:
The finishing process is effective for removing rough edges and some other surface imperfections from metal parts. The parts are placed inside of a bowl or tub which contains a pellet-shaped media. The activation of the bowl aid the vibration action that causes the media and the parts to rub against each other. Vibratory finishing process ideal for smaller parts with applications such as edge-breaking, cleaning, descaling, burnishing or polishing.
Read: Everything you need to know about metalworking
Passivation:
Passivation is a post-treatment plating process helping to provide additional corrosion protection. It is achieved by using a metal oxide coating that can lengthen the time in which the onset of rust occurs. It also enhances the appearance of the finished part as it is available in variety of colors.
Cladding:
Cladding is a mechanically process that uses heat and pressure to create bond between the substrate and the metal coating. it requires the use of specialized equipment which makes it more costly than other metal finishing process. However, cladding provide a thicker metal coating than either electroplating or electroless plating.
Electrocoating:
Electrocoating which is also known as e-coating also uses the electrodeposition principle like the electroplating process. The parts are soak in a solution containing the coating before the introduction of an electric current. But instead of metal ions, the solution contains electrically charged paint or epoxy particles that are deposited on the substrate surfaces. E-coating is often used as a primer coat on metal surface before the painting in order to promote paint adhesion. It is sometimes used to enhance the appearance of metal parts as it works well on any type of metal.
Hot blackening:
this is used to produce black matte finish mostly on automotive parts and firearms, as well as military applications where a protective dark coating is required. it is done by applying a thin black oxide coating on the surface of a substrate which helps to increase the abrasion resistance of the metal part. This metal part is allowed to travel through a series of tanks containing various cleaning agents, caustic materials and coolants. Hot blackening finishing process is generally performed in large batches, making perfect for smaller parts.
Powder Coating:
This is the application of dry power coating on metal parts instead of using liquid coating. A powder coating provides greater thickness than a liquid coating. this metal finishing process is achieved by combining some list of ingredients that includes pigments, curatives, flow modifiers, leveling agents and other additives to create the powder. The powder is then electrostatically deposited onto the surface of the substrate which is then cure in a specially designed oven. The oven produces a chemical reaction that result to high-link density. This finishing process is also applied to some plastics and other non-metallic substrates.
Electropolishing:
Electropolishing is an electrochemical metal finishing process which is the opposite way of electroplating. As electroplating involves the deposition of metal irons onto the surface of a substrate, electropolishing is the removing of metal ion from the substrate. It offers a smooth, streamlined surface texture to the workpiece. It is accomplished by dipping the objects into an electrolyte bath which serve as the anode. The object is also exposed to a terminal that provides a DC power supply that serves as the cathode. This process is ideal for removing burrs or small amount of debris from part surface and eliminating peaks and valleys.
Read: Everything you need to know about CNC machine
Abrasive Blasting:
This is also known as sand blasting or bread blasting which combine cleaning and finishing process together. Abrasive blasting saves time and money. The cleaning, polishing and finishing action is achieve when high-pressure compressed air is used to project a medium onto the surface of the parts. A wide variety of media such as sand, silicon carbide, glass beads, aluminum steel grit or shot, or organic materials like walnut shells or corn cobs. Typically, harder media is used when more aggressive cleaning action is required while soft materials are used on surfaces that are more susceptible to damage. The pressure control can also prevail in order to adjust accommodate the specific cleaning or finishing requirements.
Buff Polishing:
Buff polishing is performed to clean and smooth the surface of a substrate just as the electropolishing. But it does not involve used of any type of electrochemical reaction instead, machine equipped with a cloth wheel is used to buff the surface. The process is similar to the buffing done in automobile parts after waxing. The finishing process is applied to provide a glossy, decorative finishing to metallic parts.
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Mass Finishing:
Mass finishing is also known as mechanical surface finishing, offering a cost-effective way to polish parts in bulk. This finishing process is employ on wide range processes in order to provide uniform cleaning, edge-breaking, smoothing and polishing smaller components at once. This helps to decrease the production time and also obtain uniform surface finish on the components. The process also includes tumble finishing and vibratory finishing.
Shot Peening:
This finishing process is done to reduce metal fatigue and stress, preventing failure caused by corrosion and increase the durability and lifespan of the parts. The process is achieved by using the ball-peen hammer on the metal object which will dimple the surface. The resulting compression stress will actually strengthen the surface of the material. a special equipment is used to blast small projectiles which is known as shot. This projectile can be made of ceramic, metal, glass or other material.
Soda Blasting:
This finishing process works in a similar way to abrasive blasting. The major difference is that baking soda is applied onto the surface of the material instead of abrasive media. This process is effective in removing grease, oil, rust, paint and other surface contaminants. Soda blasting also offers a gentler cleaning action than abrasive blasting. For these reasons, it is usually employed on surfaces that are vulnerable to scratching.
Case Hardening:
This process helps to protect a metal surface and makes it harder. It is a metallurgical process that adds protection through surface modification which can be achieved by one of many techniques such as carburizing, nitriding and micro-casting. All of these processes can offer desired hard case to a metal while the underlying metal remains relatively soft. Case hardening helps to increase the durability and wear resistance of the underlying workpiece.
Tumble Slurry Blasting:
The tumble slurry blasting is also called wet blasting due to the fact that it uses hot water to provide the desired cleaning or surface preparation outcome. It is a three-part process that involves the application of an alkali hot water to prepare the surface, the blasting of an abrasive slurry onto the surface. Finally using another alkali hot water application to rinse the part. This process is totally different from other blasting processes as a high speed-blast wheel used to drive the slurry instead of compressed air.
Read: Different types of hammer used in various field
Parts Cleaning:
Parts cleaning is a very important process necessary for removing contaminants before the implementation of other industrial metal finishing process. ultrasonic washing is one of most common cleaning method where high frequency sound waves are used to produce an intensive scrubbing action. This action help to remove stubborn contaminants and debris.
Industrial Applications of metal finishing processes
The following listed below represent the applications of metal finishing process:
- Automotive
- Electronics
- Aerospace
- Hardware
- Jewelry
- Heavy equipment
- Appliances
- Telecommunications
Read: Different types of sheet metals work tools
Advantages
The following stated below represent the benefits of applying finishing treatment to metal product:
- Cleaning, polishing and removing surface defects
- Increased durability
- Reduce impact of corrosion
- Improved decorative appeal
- Enhanced electrical conductivity
- Increasing solderability
- Higher electrical resistance
- increasing wear resistance
- Higher chemical resistance
- Reducing friction effects
- Higher tarnish resistance
- Potential for vulcanization
- Strengthening the substrate
That’s it for this article “Everything you need to know about industrial metal finishing processes”. I hope you enjoyed the reading, if so, kindly comment and share. Thanks!
