Plasma coating is a process involving the use of plasma to activate the surface of components and parts during product production, facilitating chemical bonding between various atoms and forming a polymer or glassy coating. Manufacturers in the aerospace, automotive, medical devices and electronics industries use this process to modify or optimize the surface properties of base materials.
Beyond helping manufacturing companies enhance the performance and reliability of their products, integrating plasma coating into their operations can unlock the potential for innovations. Learn more about plasma surface coating and its various applications.
How Does Plasma Coating Work?
Before looking at how plasma coating works, it is helpful to understand what plasma is. Also known as the fourth state of matter, plasma is a neutral and ionized gas consisting of both negative and positive ions and free electrons. It is made by directing energy toward a gas, triggering the separation of electrons from the atomic shell and ionization of the gas.
In plasma coating, monomers are combined with the plasma feed gas. Monomers are tiny molecules that, when provided with the correct conditions, bond together to create polymers. Plasma establishes the optimal conditions on the material’s surface, quickly and efficiently facilitating bonding.
Manufacturers will use plasma to apply a thin film of around 10 nanometers to 10 microns of coating to a base material, such as a part or component. While this coating is colorless and odorless and does not impact the look or feel of the material, it produces a significant change in the physical and chemical performance of the material. Different monomers are used to give materials specific properties, such as producing hydrophilic and hydrophobic surfaces.
Which Applications Is Plasma Coating Used For?
By enhancing the characteristics of materials and transforming surface properties, manufacturers can improve their components’ capability and applicability. Additionally, product development engineers innovate and create new products that were once considered unachievable.
Here are some of the desirable characteristics that manufacturers can produce or enhance with plasma coating, as well as common applications:
- Creating hydrophobic surfaces: Materials with hydrophobic coatings result in surfaces that are resistant to water, oil, dust and aqueous solutions. Hydrophobic surfaces have many applications, like protecting plastics, ceramics, textiles, electronics and medical devices from organic contaminants and moisture.
- Creating hydrophilic surfaces: Materials with a hydrophilic coating have an extremely high surface energy, allowing water to spread evenly. These coatings increase wettability, which is a prerequisite for good adhesion. Manufacturers use plasma coatings to achieve better bond strength, helping ensure electrical parts and printed circuit boards stay in place. Hydrophilic coatings are also often applied to implantable biomedical devices.
- Creating scratch-resistant surfaces: Materials with surfaces resistant to scratches are made with a coating similar to hard glass. Manufacturing companies use scratch-resistant coatings in the production of optics-related products and components, such as lenses.
- Reducing surface friction: Manufacturers often use low-friction coatings in the production of seals, O-rings or components with tacky surfaces. These coatings are also used to avoid friction in medical devices such as artificial hips.
What Are the Different Plasma Coating Processes?
Plasma vacuum coating and plasma spray coating are two common processes used in manufacturing.
Plasma Spray Coating
The plasma spray coating process involves injecting gas feedstocks or monomers into an atmospheric plasma system, creating an atomized material stream. As plasma is essentially a superheated gas, its energized state allows it to generate extreme heat and conduct electricity. This intense heat is used to melt materials that are sprayed onto surfaces, forming a coating.
Air plasma spray is a type of plasma spray process that is complex and demands precise control. It typically comprises the following steps:
- Preparing the materials: Manufacturers begin the process by prepping the materials that will be coated, often through cleaning, to ensure proper adhesion. In addition to coating, plasma is used for various manufacturing applications, including surface cleaning.
- Generating the plasma: A fundamental aspect of this procedure revolves around creating the plasma, achieved by introducing a gas like argon to ionize the gas and produce the fourth state of matter.
- Spraying the coating: Manufacturers use various materials in plasma spray coating processes, such as ceramics, metals and polymers, selected based on the desired properties. For example, polymers are often used to achieve a low-friction coating. In a powdered form, coating materials are fed into the plasma jet, where they melt and are propelled onto the substrate. Achieving the correct speed and temperature is vital for a high-quality coating.
Upon contact with the substrate’s surface, the molten substance cools and quickly solidifies, resulting in an adherent and robust coating. Because the coating procedure takes place at an atmospheric pressure, manufacturers can produce consistent results without relying on a vacuum.
Plasma Vacuum Coating
In contrast, the plasma vacuum coating process works by introducing gas feedstocks or monomers into a plasma vacuum source. Plasma coating under a vacuum involves:
- Cleaning the surfaces: The first step is to prepare the surface that will be coated, ensuring the successful adhesion of the plasma coating to the base material. Impurities are converted into atomic particles using plasma cleaning methods and are then removed with extra gas feedstock from the vacuum chamber.
- Activating the surface: In the plasma vacuum coating procedure, activation is an extension of the cleaning step, transitioning from one stage to the next within the vacuum chamber. Plasma activation prepares the substrate by increasing its surface energy, improving its adhesion properties to support the coating more effectively.
- Coating the surface: The coating step begins by injecting a vaporized monomer or bottled flas feedstock into the vacuum, which serves as the coating material. Next, manufacturers apply an electric charge to create gas ions, radicals and molecules in an energetic state, which is the plasma. The interaction between the monomer and plasma results in monomer activation and subsequent polymerization — the monomers turn into polymers that adhere to the substrate’s surface.
Plasma Spray Coating vs. Vacuum Coating: Which Is Best?
While manufacturers have traditionally favored implementing coating procedures in vacuum chambers, the ion bombardment that is intrinsic to this method can damage fragile components and materials. This poses a significant challenge to industries where plasma coating is key to production processes. For example, there is the risk that ion bombardment roughens the surface or dislodges a piece of the substrate being coated.
Additionally, as this method requires a vacuum environment, manufacturers may be restricted in the shape and size of substrates that they can coat, as well as how many. They may also be limited in the thickness of the coating they’re able to achieve, as vacuum coating is commonly used for applying thin films.
In comparison, the plasma spray coating method offers precise control over the thickness of the coating, allowing for customization to specific application needs. The coatings produced via this process also tend to be extremely dense, decreasing porosity and enhancing the protective characteristics of the coating. As a result, spray coating is ideal for the automotive, aerospace, electronics and medical device industries.
Since spray coating occurs under atmospheric pressure conditions, parts or components do not need to be added to a vacuum in batches for coating, allowing for processing in a continuous line. With more process control, manufacturers typically experience increased uptime. Without the potential for party damage and the downtime associated with vacuum coating, implementing spray coating processes can help companies reduce losses and operating expenses.
Implement Spray Coating Processes With Surfx Technologies
Surfx Technologies offers argon plasma to global manufacturing companies that specialize in automotive and aerospace technology, medical devices, electronics and semiconductors. Our plasma is atmospheric, so it eliminates the need for a chamber. It is also weakly ionized, meaning it is safe for coating sensitive parts, such as microelectronics. With our plasma treatment machines, you can streamline your surface preparation procedures, too.
Request a demo to experience our industry-leading plasma solutions, or contact us if you have any questions.