Coatings are layers of material applied to a substrate to improve its surface qualities for wear and corrosion resistance, according to surface engineering. Several pairs of factors affect the choice of coating, including component size and shape, life expectancy, substrate material compatibility, service environment, and cost.
There are many coating methods for adding different kinds of material at thicknesses that run from a few microns to several millimeters. These coatings can be classified in numerous ways. One typical approach is coating material deposition on the substrate surface. This covers bulk coating or cladding, atomic deposition, and particle deposition.
In this reading, we’ll explore several types of coating and discuss their uses.
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Types of Coating
While there are a variety of industrial coatings available, each with its own set of physical and chemical properties (e.g., resistance to corrosion, UV performance, etc.), no one coating can meet a structure’s protective requirements. This is why assets are often covered in multiple layers of protective coating to create a system that offers complete chemical, physical, and galvanic protection to the substrate.
Polyurethane Coatings
A polyurethane coating is a protective layer of polyurethane that is applied to a substrate’s surface. These coatings aid in preserving substrates from a wide range of damage, including weathering, corrosion, abrasion, and more.
The polymer polyurethane itself is linked to a group of chemical compounds called carbamates. Also, this polymer does not melt but rather burns when heated, making it thermosetting. The adaptability of polyurethane coatings is another quality that sets them apart.
It is possible to formulate these coatings to be opaque, transparent, glossy, or muted. Even while polyurethane coatings seem a lot like other coatings (like epoxy), they have a lot of unique qualities that make them perfect for certain uses.
Coatings made of polyurethane are more elastic and softer than epoxy ones, but they are still more enduring. Because of this quality, floors coated with polyurethane are great for areas with moderate to heavy foot activity.
Floors made of polyurethane are slightly springy due to their reduced rigidity, which makes them resilient to impacts. They are less likely to have dents and scratches because of how durable they are. Because of their enhanced flexibility, polyurethane flooring can keep their form and mechanical qualities down to temperatures as low as -30°F (-1°C).
Epoxy Coatings
Epoxy coatings are long-lasting paints and coatings for both flooring and metals; they are also strong adhesives. An epoxy coating is created by combining an epoxide resin with a polyamine hardener, which causes a chemical reaction.
A “curing” process is the end effect of combining these two substances. The epoxy coating goes from a liquid to a solid in a matter of minutes to hours. This transformation makes the coating very sturdy and long-lasting.
Epoxy and epoxy coating compounds have several uses due to their ability to form a product that is strong, long-lasting, and resistant to chemicals. Many electrical, automotive, marine, composite, and industrial manufacturing plants use epoxy coatings. Epoxy coating compounds and epoxy materials have several uses as long-lasting adhesives.
Ceramic Coatings
Ceramic coatings, sometimes referred to as nano coatings, glass coatings, or quartz coatings, are semi-permanent coatings that can be applied to various surfaces to prevent environmental damage and to make cleaning and maintenance simpler.
Many industries, including the automotive, textile, maritime, heavy equipment, and construction industries, use several kinds of these nano coatings. Applying a ceramic coating to the car’s exterior paint (and other surfaces) serves as a sacrificial layer to shield it from dirt, UV rays, environmental debris, and small scratches and swirls.
Polysiloxane Coating
Industries that deal with abrasion, chemicals, intense ultraviolet light, and high temperatures regularly use polysiloxane coatings for protection and maintenance. Polysiloxane is shorthand for polymers that contain a silicon-oxygen backbone.
Organic polymers’ carbon-carbon backbone is much more easily damaged by UV light than silicon-oxygen backbone. In terms of chalk resistance and gloss preservation, polysiloxanes offer outstanding aesthetic weathering qualities.
Due to their low volatile organic compound formulation, they are resistant to abrasion, corrosion, chemicals, and dirt pickup, and they also have good anti-graffiti qualities.
Polysiloxane chemistry has led to the development of three major categories of coatings: inorganic polysiloxanes, epoxy-polysiloxane hybrids, and acrylic-polysiloxane hybrids. Inorganic polysiloxanes can resist temperatures up to 1,400°F, while epoxy-polysiloxane hybrids offer weather and corrosion resistance.
Acrylic-polysiloxane hybrids combine acrylic and siloxane resins for a low VOC, highly weatherable topcoat. Polysiloxane coatings are used in various industries, including structural steel and power plants.
Anodizing
The electrochemical process of anodizing is primarily used to coat aluminum and other metals. An electrolytic solution and electric current generate a protective oxide layer on the metal’s surface.
If you want a decorative finish, you can dye this layer in different colors. This coating is only appropriate for aluminum and can be more costly, but it improves the metal’s inherent resistance to corrosion, adds a decorative touch, and protects it from UV rays.
Acrylic Coatings
One of the most widely used conformal coatings nowadays is acrylic. The coatings consist of a single component, namely pre-formed acrylic polymers that are applied to surfaces after being dissolved in a solvent.
Acrylics have exceptional fungal resistance and are a great barrier against moisture and humidity, which is why electronic equipment often uses acrylic coatings. They take on the shape of an electronic device, shielding the whole surface from physical, electrical, and gaseous problems as well as UV rays, humidity, condensation, and liquid.
Furthermore, the coatings generate little to no heat when curing, which is great for electronics that are sensitive to heat. Acrylic coatings are mostly employed in architecture, decor, industry, and finishing. They are also applicable to powders, formulations, and radiation-curable materials that contain organic solvents.
Zinc-Rich Coatings
A coating with a high concentration of zinc dust, known as a zinc-rich coating, serves as a protective layer for steel when the two materials come into direct touch. The use of zinc-rich coatings prolongs the life of steel surfaces and prevents corrosion.
Similar to cold galvanizing, zinc-rich coatings offer metals cathodic protection. Many industries employ zinc-rich coatings to prevent corrosion on steel substrates. They are used in industrial, automotive, highway, and infrastructure applications.
Zinc-rich coatings are frequently top-coated with paint or epoxy; however, they can be an independent coating. Under a top coat of epoxy or urethane paint, this primer offers an extra or backup way to prevent corrosion on the steel.
Zinc coatings come in two types: inorganic, which requires spraying and offers better steel protection, and organic, which can be applied using a brush, roller, or spray. Organic coatings provide similar protection when top-coated and can be a moisture-cured urethane primer.
Powder Coating
A lot of people like powder coating metals since it lasts a long time, does not harm the environment, and comes in a variety of colors and finishes. This dry finishing method entails coating the metal surface with powdered paint that is heated and dried to provide a protective coating.
Durable, eco-friendly coating for architectural metalwork, outdoor furniture, appliances, and automotive parts, available in various colors and finishes, but may be expensive and not suitable for all metal types.
Galvanizing
Galvanizing is the process of treating metal with a layer of zinc to prevent corrosion. The two most common methods for doing this are electro-galvanizing, which applies the zinc coating using an electric current, and hot-dip galvanizing, which involves dipping the metal into a bath of molten zinc.
This product is long-lasting, reasonably priced, and provides good corrosion protection. It can be powder-coated or painted for aesthetic purposes, but it is not suitable for other metals.
Electroplating
The process of electroplating entails applying an electric current to a metal surface in order to deposit a thin layer of metal, such as chrome, nickel, or gold. This can improve the metal’s wear and corrosion resistance while also adding a cosmetic finish.
Nitro Coat
These coatings stand out in the industry thanks to their unique combination of surface-enhancing qualities. They have outstanding surface hardness, are resistant to galling, have anti-friction properties, and can tolerate extremely high temperatures.
Nitro coat is the best option among high-performance choices. Modern technology is used to chemically apply nitrocoat barrier coatings. These coatings generate dense, thin, and incredibly homogeneous layers on the majority of metallic substrates with ease.
The Nitro coat system ensures that components operate exceptionally well in both harsh field circumstances and thorough laboratory testing.
Intumescent Coatings
An intumescent coating is a type of coating that is specifically designed to protect combustible and susceptible substrates. When in their natural form, intumescent coatings appear smooth, exactly like most other paints.
It acts as an insulating layer and delays the time it takes for the structure to fail because it rapidly expands and creates a char when exposed to heat or flames, which lessens the passage of heat from the fire to the underlying substrate.
By slowing the development of a structure fire, intumescent coatings give first responders more time to put out the fire and provide inhabitants more time to flee. Furthermore, in an emergency, intumescent coating aids in preventing damage and safeguarding the building’s structural integrity.
Metallic Coating
Metal coating is the process of applying a metallic or other surface finish to metal and nonmetal items to prevent rust and corrosion brought on by exposure to various environmental factors, including water, chemicals, and air.
Many manufacturing organizations utilize this technology to help prevent corrosion or damage to their finished products. Many different manufacturing industries use coatings in their products.
Some examples include electronics, appliances, automotive, aviation/aerospace, structural metal buildings and other structures, and marine.
Related: What is Galvanization? Its Application, Types & How it Works
E-Coating
E-coating, also known as electrophoretic coating, is a technique that applies paint to a metal surface by submerging it in a water-based paint solution and then using an electric current to apply the paint.
As a result, the finish is consistent and resistant to corrosion. It offers a uniform, corrosion-resistant finish with low VOC emissions but has limited color options and durability compared to powder coating.
PVDF (Polyvinylidene Difluoride) Coatings
One of the most notable properties of PVDF—a pure fluoropolymer—is its resistance to heat, acids, solvents, and bases, in addition to its great strength and purity. When there is a fire, it also produces very little smoke.
PVDF is perfect for corrosion-resistant coatings and long-lasting architectural treatments for building panels since it dissolves in polar solvents like amines and organic esters at high temperatures. Melting PVDF for use in injection molding or extrusion is simple.
Water treatment, nuclear waste processing, the paper and pulp industry, high-purity semiconductor markets, and chemical processing all make extensive use of it. PVDF also satisfies the exacting standards needed by the pharmaceutical and food processing sectors.
Teflon Coatings
Teflon is more of a brand name than an actual product. It refers to the chemical coating polytetrafluoroethylene (PTFE). This type of plastic is sprayed on a variety of objects and baked to provide a surface that is nonreactive, waterproof, noncorrosive, and nonstick.
In this manner, it establishes a protective barrier between the product and potential hazards from the outside world. Although PTFE coating finds application in many other industries, its most well-known uses are in the automotive, chemical, oil and gas, and bakeware sectors.
Slide gates, hinges, blades, AC pistons, springs, bearings, steel, lawn and garden equipment, and guide rails are a few examples of end uses for PTFE coatings.
Fluoropolymer Coatings
Fluoropolymer coatings are mixtures of fluoropolymer lubricants and high-performance resins. A high-quality dry film lubricant is present in these coatings. The result is a glossy, strong, smooth coating with superior chemical and corrosion resistance.
Also, fluoropolymer coatings reduce friction, galling, non-stick, non-wetting, electrical resistance, and abrasion. Fluoropolymer coatings are used on a wide range of OEM components and fasteners to extend their lifespan before needing to be replaced.
Excalibur Coatings
Excalibur Coatings will significantly outperform conventional fluoropolymer coatings anywhere there are severe wear resistance requirements. A special coating application provides excellent non-stick and release properties and strong abrasion resistance.
When it comes to nonstick coating systems, Excalibur Coatings are the strongest, longest-lasting, and most durable option. They provide better solutions for a variety of industrial needs.
It improves plastic welding speed in the packaging industry, cutting knife lifespan in the food industry, roller cleanability in the printing industry, and adhesive release in automotive assembly processes.
Xylan Coatings
The purpose of xylan coating, an extreme performance coating, is to increase the functionality and lifespan of a variety of consumer and industrial goods. Xylan coatings provide a plethora of beneficial qualities, which makes them an attractive option.
In harsh environments like saltwater and road chemicals, xylan coatings improve product functionality and durability by preventing corrosion and chemicals. Additionally, Xylan-coated products withstand deterioration from sunlight and harsh weather.
Xylan is a versatile coating for a wide range of items since it sticks to several materials, including wood, ceramics, metals, and plastics. Additionally, xylan coatings have outstanding non-stick and release qualities that make them beneficial for industrial manufacturing as well as cookware applications.
PPS And Ryton Coatings
The resin-bonded polymer systems that make up these coatings are renowned for their remarkable resistance to thermal deterioration and chemical reactions. Up to 500°F (260°C), they are essentially unaffected by solvents, which makes them a preferred option in the chemical processing sector.
PPS coatings work well as a primer under a topcoat or as a stand-alone coating for superior chemical and corrosion protection. PPS coatings provide exceptional abrasion and wear resistance in addition to their thermal and chemical advantages.
ECTFE (Ethylene And Chlorotrifluoroethylene) Coating
These coatings provide dependable electrical properties and outstanding chemical resistance. If your application requires more heat and chemical resistance than PVDF can provide, then an ECTFE coating is the best option.
Molybdenum Coatings
The main purpose of these coatings is to improve material performance by raising the friction coefficient, operating temperature, and load-bearing capacity. They frequently surpass 250,000 psi and offer efficient lubrication across a broad variety of loads.
Moly coatings provide sacrificial lubrication, which lowers wear and friction by moving fluid between mating surfaces. Molybdenum coatings blend molybdenum disulfide lubricant with high-performance resins. Thermal curing ensures that the coating forms a firm bond with the coated part’s base metal.
Types Of Coating By Application/Purpose
Coatings are useful for more than just looking good; they also protect the substrate (the area that gets coated). Here are the types of coatings by their application or purpose:
Protective Coatings
Protective coatings are the initial line of defense for materials in the face of mechanical and environmental wear. Coatings like this protect materials against rust and scratches and keep them in good condition for a longer period.
The two most common coating types in this area are epoxy and polyurethane. Industrial floors and metal structures are ideal subjects for epoxy coatings due to their high adherence and exceptional chemical resistance.
Automotive finishes and industrial applications frequently make use of polyurethane coatings due to their long-lasting nature and resilience to ultraviolet radiation. Protective coatings play an essential role in the infrastructure industry.
They protect structures, pipelines, and bridges from deterioration and rust. Coatings like this are also vital to the automotive industry, which uses them to keep vehicles looking good and prevent rust.
Protective coating technology is always evolving to make these coatings last longer and work better, even in the most challenging environments.
Functional Coatings
Coatings with improved electrical conductivity, reduced friction, or increased hardness are examples of functional coatings. Glasses and screens with anti-reflective coatings, for instance, make things more comfortable and easy to see by reducing the amount of reflections and glare.
Hydrophobic coatings prevent fouling and are easy to clean since they do not allow water to penetrate. Optical and electrical fields cannot function without effective coatings. They make electronics more reliable and enhance the functionality of lenses and screens.
Frequently, they supply the essential features that are required by technological applications. This field has seen a dramatic shift due to the application of nanotechnology. Coatings with hitherto unseen qualities and performance levels are now within reach.
Decorative Coatings
Coatings do more than only protect; they can modify an object’s visual appeal. Paints and lacquers are decorative coatings that add gloss, texture, and color to products. When it comes to branding and product differentiation, these coatings are crucial.
Coatings add visual appeal, brand identification, and tactile sensation to consumer goods like electronics and home decor. The decorative coatings business is experiencing a period of rapid innovation as a result of shifting consumer preferences towards more sustainable and environmentally friendly solutions, as well as personalized finishes.
Specialty Coatings
Applications that call for a unique blend of aesthetic, protective, and practical qualities are the ones that inspire the creation of specialty coatings. Equipment can have insulation coatings put on them to keep heat in and fire-retardant coatings applied to building materials to stop the spread of fire. Aerospace and marine industries are two industries that make use of these coatings.
Types Of Coating By Application Method
The following are the types of coating based on application method:
Roll Coating
Coatings are applied to big, flat surfaces using paint rollers. In a coating trough, the rollers rotate, collecting a specific quantity of coating material. It creates a roller-surface wet film of a specified thickness. The coating substance is smoothly applied to the substrate’s surface as the roller rotates and makes contact with it, producing consistent coating finishes.
Roll coating works incredibly well for UV and baking coatings, which require coatings with superior adhesion, leveling, and wetting properties. The coating should ideally cure quickly and produce a film in a short amount of time.
Roll coating greatly increases efficiency and streamlines continuous production operations. Roll coating, on the other hand, works best on large, flat surfaces and cannot guarantee a high-quality coating finish on objects with varying shapes.
Spray Coating
Spray coating is carried out by propelling a stream of air through the central orifice of the spray gun with compressed air at a pressure of 0.2 to 0.5 MPa. By doing this, a negative pressure zone is formed at the front end of the nozzle, which draws the coating material from the container.
The coating substance is subsequently expelled from the nozzle and quickly enters the compressed airflow. This atomizes the liquid, creating a paint mist that flies toward and sticks to the covered object, creating a continuous covering film.
Dip Coating
Dipping is an old-fashioned coating process that works well with streamlined workpieces that have straight lines, flat surfaces, and no recesses or paint pockets because of its adaptable operation and minimal equipment requirements. That said, it will not work well on surfaces that have blind holes, deep grooves, or places where excess paint is tough to wipe off.
The process of dip coating involves submerging the entire component in a tank of liquid paint. The workpiece is taken out of the paint after a brief soaking time, which causes the paint to stick to the surface and create a coating. Excess paint drips back into the paint tank.
Brush Coating
Brush coating is a way to put paint on by rubbing the substrate’s surface directly with a paintbrush. This makes sure that the surface is evenly wet and coated to form a paint film. It is ideal for coating items of any shape and is one of the most straightforward painting techniques.
Brush coating has several benefits, such as ease of use, paint savings, low tool requirements, and broad applicability. It works with a variety of materials and shapes. Brush coating is quite versatile and works well with nearly all paint types, with the exception of those that dry too quickly.
The mechanical motion of the brush allows for effective wetting of the substrate’s surface, entering small pores and increasing the adhesion of the paint coat. Nonetheless, brush coating is significantly less efficient than other coating methods.