Spray Coater: Working Principles and Uses
Jump to: How Does A Spray Coater Work? | Spray Coaters in Industry | Spray Coaters in Research | Spray Coating Systems | Spray Coating Advantages
A spray coater is a piece of equipment that facilitates the coating of a solution onto a surface using spray coating methods. Spray coating involves breaking up a coating solution into tiny droplets and directing this spray towards a coating surface using pressurized gas. As the droplets hit the surface, they coalesce to form a continuous film.
Spray coaters are versatile and can be used to coat large area substrates with relative ease. These techniques are regularly and reliably used in industry for protective, aesthetic and functional coatings. Spray coating offers several advantages over other deposition techniques including flexible coating of curved or irregular substrates, and relatively low levels of material waste compared to processes like spin or dip coating.
How Does A Spray Coater Work?
Spray coaters usually consist of three main components:
- Spray coating head
- Head movement System
- Solution and gas delivery system
The specifics of these components differ significantly between different systems, but they all need to co-ordinate well together to form an efficient spray coating system.
The spray formation process occurs within the spray coating head. This process has two steps:
- Break up or atomize the coating liquid into suitable droplets
- Shape and direct the newly formed “spray” towards the coating surface
These steps are done almost simultaneously and transform the spray coating solution into a mist or spray that's shaped into a controllable jet of atomized liquid.
Throughout this process, a continuous stream of both coating liquid and gas must be delivered to the head, requiring a controlled fluid delivery system. Additionally, there must be controllable XYZ movement of either the spray coating head or the coating surface to coat over the entire surface area.
By optimizing the coating head speed, distance between the head and substrate and the solution flow rate you can tailor your process to get a good spray-coated film. Depending on the type of head you are using, you will also need to optimize either the ultrasonic frequency or the rate of gas flow in order to change your spray.
Spray Coater Applications in Industry
Spray coating is used in many industrial sectors due to its scalability and flexibility. Some example applications include:
- Manufacturing: Throughout various industries, spray coated films improve the durability, wear resistance, and corrosion resistance of many machines and components that need to last for years in factory settings.
- Electronics & Display Coatings: Spray-coated conductive polymers can form transparent, flexible electrodes used in touchscreens and displays.
- Functional and Protective Layers: Spray coating techniques are used in the creation of smart windows, sensors, and surface treatments where custom shapes and rapid deposition is very important.
- Automotive Industries: Spray coating processes are great for coating the curved surfaces of car parts.
- Energy Sectors: Spray deposition methods are used to coat wind turbine blades and it is also used for specialized protective coatings on pipelines and valves.
Spray Coater Applications in Research
At some stage, any researcher working on thin film devices or coating layers must consider how their materials can be produced on a large scale. This is known as scalability and some techniques are much more scalable than others.
The most common technique used in wet film research is spin coating. However, this technique can’t coat large areas easily and isn’t suitable for large scale manufacturing. Spray coating is a well-established deposition method used in many industrial processes. Therefore, the ability for researchers to experiment with spray coating on a laboratory scale helps to make early prototypes of exciting new technology, taking research from the lab to market more quickly.
Different Spray Coating Systems
The method spray coaters use to break solutions into tiny droplets, or the atomization process, is important. Example atomization methods include:
- Air-assisted spray coating: Where compressed gas shears the liquid into droplets. This can happen:
- Within the spray coating head (internal mixing)
- Outside of the spray coating head (external mixing)
- Hydraulic spray, where the solution is forced through a narrow nozzle at high pressure.
- Ultrasonic spray, where high-frequency vibrations generate a fine, uniform mist.
Choice of method influences droplet size, distribution, and ultimately, film quality.
Once droplets land on the substrate, film quality depends on solvent evaporation, droplet coalescence, substrate wetting, and spray parameters such as nozzle settings and spray distance.
Why Use A Spray Coater?
There are many advantages of using a spray coater. Some of these include:
Reliable coating over large areasSuitable for coating irregular or curved surfacesCompatible with roll-to-roll processingPlenty of parameters to optimizeHigh levels of deposition controlQuick deposition speeds
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