What is coating?
From a surface engineering point of view, a coating is a layer of material deposited onto a substrate to enhance its surface properties for corrosion and wear protection.
Factors affecting the choice of a coating include service environment, life expectancy, substrate material compatibility, component shape and size, and cost.
There is a wide range of coating processes for depositing many different types of material at thicknesses ranging from just a few microns, up to several millimetres. The different types of coatings can be categorized in many ways.
One common approach is based on how the coating material is deposited on the substrate surface. This includes atomic deposition, particulate deposition, and bulk coating or cladding.
Types of Coatings
Different types of industrial coatings have different chemical and physical properties corrosion resistance, performance when exposed to UV, etc. but no coating provides all the protection a structure needs.
That’s why assets are coated with one or more coating types to form a total protective coating system, or a system providing all the chemical, physical, and galvanic protection required to protect the substrate from its environment.
Understanding the most common generic coating types and how they work together to form a total protective coating system allows designers and owners to choose the system best suited for their prevailing service location.
Before choosing the right coating, you must know about the different types of coatings.
#1. Epoxy Coatings.
Epoxy coatings are durable coatings that can be used for a variety of purposes from strong adhesives to durable paint and coatings for floors and metals. Epoxy coatings are created through the generation of a chemical reaction using an epoxide resin and a polyamine hardener.
When these two chemicals are combined, a process called “curing” results. This process can take anywhere from several minutes to several hours and turns the liquid epoxy coating into an extremely strong and durable solid.
Because of their ability to create a strong, durable, and chemically resistant substance, epoxy and epoxy coating compounds can be used for a variety of purposes.
You can find epoxy coatings used throughout industrial manufacturing plants, in composite materials such as carbon fiber and fiberglass, and in a variety of electrical, automotive, and marine applications.
Epoxy materials and epoxy coating compounds can also be used as durable adhesives in a variety of applications.
#2. Polyurethane Coatings.
A polyurethane coating is a polyurethane layer applied to the surface of a substrate for the purpose of protecting it. These coatings help protect substrates from various types of defects such as corrosion, weathering, abrasion, and other deteriorating processes.
Polyurethane itself is a type of polymer that is connected to a chemical compound group known as carbamates. This polymer material is also thermosetting in nature; in other words, it burns rather than melts when heated.
Another characteristic of polyurethane coatings is its customizability. These coatings can be formulated to be glossy, muted, opaque, or transparent.
While polyurethane coatings may appear to be visually similar to other coatings (e.g., epoxy), they possess several distinct properties that make them ideal for specific situations.
While polyurethane coatings are relatively durable, they are softer and more elastic than their epoxy counterparts.
This attribute makes polyurethane-coated floors ideal for moderate to heavy pedestrian traffic. The reduced stiffness gives polyurethane floors a slight springiness, allowing them to absorb sharp impact loading.
This durability also makes them more resistant to abrasion and less prone to dents and scratches.
Improved elasticity also means that polyurethane floors can maintain their shape and mechanical properties in temperatures lower than 30°F (-1°C).
#3. Polysiloxane Coating.
Polysiloxane Coatings are industrial protective and maintenance coatings that are used in services characterized by abrasion, chemicals, extreme UV, and high temperatures. The term polysiloxane refers to a polymer with a silicon-oxygen backbone.
The silicon-oxygen backbone is much more resistant to the effects of UV radiation than the carbon-carbon backbone of organic polymers. Polysiloxanes have excellent aesthetic weathering attributes in terms of gloss retention and chalk resistance properties.
They exhibit excellent abrasion and corrosion resistance, good chemical resistance, good anti-graffiti properties, and resilience to dirt pickup, and are formulated with low VOC‘s.
Advances in polysiloxane chemistry have resulted in the development of three major categories of this type of coating:
Inorganic Polysiloxanes: Typical inorganic polysiloxanes cure by hydrolytic polycondensation. Formulated with the proper selection of additives and pigments, coatings can resist temperatures of approximately 1,400°F (760°C). Variation of pigment creates coatings with excellent solvent resistance.
Epoxy-Polysiloxane Hybrids: Formulation with aliphatic epoxy resins, silicone intermediates, oxysilanes, and aminosilanes creates weather and corrosion-resistant hybrids. These coatings are cured by both hydrolytic polycondensation and more conventional epoxy-amine mechanisms, resulting in what are known as interpenetrating polymer networks. The resulting formulations provide improved resistance to weathering over conventional epoxy coatings.
Acrylic-Polysiloxane Hybrids: By combining acrylic and siloxane resins, a low VOC, highly weatherable topcoat is produced. These systems can be produced as one- or two-component systems.
New chemical variants in polysiloxane coating chemistry are continuing to be developed at a rapid rate. Each manufacturer of polysiloxane coatings makes a compatible primer and intermediate/tie coat.
PolySiloxane Coatings are used on structural steel, steel tanks, barges, refineries, petrochemical plants, power plants, railcars, pulp & paper mills, masonry surfaces, and others as recommended.
#4. Alkyd Coatings.
Alkyd coating is an enamel finish that has a similar consistency to oil paint. They usually have thinners made from either alcohol or mineral spirits.
However, alkyd quick-dry primers and topcoats can’t be thinned with mineral spirits. The type of thinner used will control how the paint flows as well as the drying time.
Because the binder in an alkyd coating is a strong resin, it is very resistant to damage. Therefore, many people use them in high-traffic areas of their homes such as hallways.
The resin binder is also resistant to moisture; therefore, it is a good coating for use in the kitchen or bathroom.
People with children often like alkyd coating in areas where the children will be playing. Latex paint coating isn’t quite as durable as many types of alkyd coating. Furthermore, alkyd coating retains its sheen for much longer than other types of Paint coatings.
Due to the strong adherence of the resin binder, you can actually apply alkyd coating over latex paint. You can also apply it over unfinished wood.
If you want to paint an area without as much preparation or without stripping the old paint, alkyd coating is your best option.
#5. Zinc-Rich Coatings.
A zinc-rich coating is a coating that contains a high percentage of zinc dust and acts sacrificially when in direct contact with steel.
Zinc-rich coatings are applied to protect steel surfaces from corrosion and extend the surface’s life. Zinc-rich coatings provide cathodic protection to metals similar to cold galvanizing.
Zinc-rich coatings are used by many industries to protect steel substrates from corrosion. They are used in highways and infrastructure, industrial and automotive applications.
Although a zinc-rich coating can be used as a standalone coating, it is often top-coated with paint or epoxy. This primer provides a backup or additional method to protect the steel from corrosion under a top coat of epoxy or urethane paint.
There are two types of zinc coatings:
- Inorganic: Inorganic zinc coatings must be applied by spraying. Inorganic zinc coatings provide better steel protection than non-top-coated organic zinc coatings when not using a top coat.
- Organic: Organic zinc coatings are normally applied by brush, roller, or spray. When not using a top coat, they do not protect the steel as well as an inorganic primer. Organic zinc coatings do provide the same degree of protection as inorganic coatings when the coating is top-coated. Organic zinc coatings can be a moisture-cured urethane zinc primer, which is easy to apply to a surface.
#6. Acrylic Coatings.
Acrylic coatings are one of the most common conformal coatings used today. The coatings are single-component materials; more specifically, they are pre-formed acrylic polymers that are dissolved in a solvent to be applied to surfaces.
Acrylics provide an excellent barrier to both moisture and humidity and have good fungus resistance; these properties are why acrylic coatings are so frequently used on electronic circuitry.
Acrylics conform to an electronic device’s shape, protecting the entire surface from moisture, electrical, and physical issues, including gases, UV exposure, humidity, condensation, and liquid.
In addition, the coatings give off minimal to no heat during the curing process, which is beneficial for heat-sensitive electronics.
Acrylic coatings are most widely used in architectural industries, decorative, industrial goods, and finishes. They can also be used in organic solvent-borne, radiation-curable formulations, powders, etc.
#7. Ceramic Coatings.
Ceramic coatings, also known as nano coatings, glass coatings and quartz coatings, are semi-permanent coatings applied on different surfaces to protect them against environmental damage and make them easier to clean & maintain.
Different variants of these nano coatings are used in different industries like automotive, textiles, marine, heavy equipment, construction and many more.
Ceramic coating for the car is a sacrificial layer that is applied on the car’s exterior paint (& other surfaces) in order to protect it from environmental debris, UV rays, dirt, and minor swirls and scratches.
#8. Intumescent Coatings
An intumescent coating is a coating that is specially formulated to protect vulnerable and flammable substrates. When in its natural state, intumescent coatings look smooth—just like most other paints.
However, when exposed to heat or flames, it quickly expands and forms a char that reduces the transfer of heat from the fire to the underlying substrate, thereby acting as an insulating layer and delaying the time it takes for the structure to fail.
The purpose of intumescent coatings is to slow the spread of a building fire, allowing more time for occupants to escape and for first responders to extinguish the fire.
Additionally, intumescent coating helps prevent damage and protect the structural integrity of the building itself during an emergency.
#9. Metallic Coating.
Metal coating refers to the process of covering metal and nonmetal objects with a metallic or other surface finish to protect the surface from rust and corrosion caused by different environmental exposures such as air, chemical exposure, and water.
This technique is used by many manufacturing companies to help protect their finished products from getting damaged or corroded.
Manufacturing industries, such as electronics, appliances, automotive, aviation/aerospace, structural metal buildings and other structures, and marine, to name a few examples, use coatings in their products.
#10. Teflon Coatings.
Teflon is not a product on its own, but a brand name of a product. It refers to a chemical coating known as polytetrafluoroethylene (PTFE).
It’s a type of plastic sprayed on various items and then baked to create a nonstick, waterproof, noncorrosive, and nonreactive surface. This way, it creates a barrier between the product and the external elements that can harm it.
PTFE coating is used in a variety of industries, but is most known for its use in bakeware, automotive, chemical, and oil and gas.
Some common end uses for PTFE coatings include slide gates, hinges, blades, AC pistons, springs, bearings, automotive components, steel, lawn and garden equipment, and guide rails.
#11. Excalibur Coatings.
Wherever extreme requirements for wear resistance are present Excalibur Coatings will exceed common fluoropolymer coatings by far.
This is achieved by a unique coating application achieving outstanding non-stick and release properties, combined with a very high resistance against abrasive wear.
Excalibur Coatings are the toughest, longest-lasting, most durable nonstick coating system – offers improved solutions within a wide range of industrial requirements.
In the food industry it leads to longer lifetime for cutting knifes, improved clean-ability for rollers in the printing industry or better release of glue in automotive assembly processes while the packaging industry benefits from higher speed in plastic welding processes.
#12. Xylan Coatings.
Xylan coating is an extreme performance coating, explicitly designed to improve the performance and extend the life of various industrial and consumer products. There are several advantages to using Xylan coatings, thanks to a long list of desirable properties.
Xylan coatings improve the functionality and longevity of many products, providing both chemical and corrosion resistance under demanding conditions, such as saltwater or road chemicals.
Products coated with Xylan are also resistant to extreme weather conditions and degradation from sunlight.
Xylan adheres to a variety of materials from metals and plastics, to ceramics and wood, making it a versatile coating for a diverse range of products.
Xylan coatings also have excellent non-stick and release properties, useful from cookware applications to industrial manufacturing.
#13. Fluoropolymer Coatings.
Fluoropolymer coatings are blends of high-performance resins and fluoropolymer lubricants. These coatings contain a superior dry film lubricant. The final product produces a smooth, hard, slick coating that provides excellent corrosion and chemical resistance.
Other benefits of fluoropolymer coatings include reduced friction, resistance to galling, non-stick, non-wetting, electrical resistance and abrasion resistance.
Fluoropolymer coating applications are extensive; the coatings are applied to fasteners and various OEM components to provide a longer life before replacement.
#14. Nitro Coat.
These coatings offer a distinctive blend of surface-enhancing properties that stand out in the industry.
They are engineered to withstand extreme temperatures, feature exceptional surface hardness, resist galling, and provide anti-friction benefits. Among high-performance options, Nitro coat is the preferred choice.
Nitro coat barrier coatings are chemically applied using cutting-edge technology. These coatings are effortlessly applied to most metallic substrates, resulting in thin, extremely uniform, and dense layers.
Components coated with the Nitro coat process consistently exhibit outstanding performance under both extreme field conditions and rigorous laboratory testing.
#15. Molybdenum Coatings.
These coatings are primarily designed to enhance material performance by increasing operating temperature, load-bearing capacity, and friction coefficient. They provide effective lubrication across a wide range of loads, often exceeding 250,000 psi.
By transferring lubricant between mating surfaces, moly coatings offer sacrificial lubrication, which helps reduce both friction and wear.
Molybdenum coatings combine high-performance resins with molybdenum disulfide lubricant. The coating is thermally cured to ensure a strong bond with the base metal of the coated part.
#16. PPS And Ryton Coatings.
These coatings are resin-bonded polymer systems known for their exceptional resistance to chemical reactions and thermal degradation. They remain virtually unaffected by solvents up to 500°F (260°C), making them a popular choice in the chemical processing industry.
PPS coatings can be used alone for excellent corrosion and chemical resistance or as a primer beneath a topcoat. In addition to their thermal and chemical benefits, PPS coatings offer outstanding abrasion and wear resistance.
#17. PVDF (Polyvinylidene Difluoride) Coatings.
PVDF is a pure fluoropolymer known for its exceptional strength, purity, and resistance to acids, solvents, heat, and bases. It also generates minimal smoke during fires.
At high temperatures, PVDF can dissolve in polar solvents like amines and organic esters, making it ideal for corrosion-resistant coatings and durable architectural finishes for building panels.
PVDF can be easily melted for extrusion or injection molding applications. It is widely used in high-purity semiconductor markets, the paper and pulp industry, nuclear waste processing, water treatment, and chemical processing.
Additionally, PVDF meets the stringent specifications required by the food and pharmaceutical processing industries.
#18. ECTFE (Ethylene And Chlorotrifluoroethylene) Coatings.
These coatings offer exceptional chemical resistance and reliable electrical properties. ECTFE coatings are ideal for applications requiring superior thermal and chemical resistance beyond what PVDF can provide.