Thermal spraying is a process used for coating metal parts. The process uses thermal energy to deposit a layer of protective material on the surface of another object. The result is a finish that is smooth and corrosion-resistant, which protects against moisture, abrasion, and other elements.
This protective coating also increases the aesthetic value of the object. In this blog post, you will learn more about thermal spraying as a protective metal coating and its different applications in industries such as mining, pulp and paper, construction, oil, and gas.
What is Thermal Spraying?
Thermal spraying, also known as flame spraying or flame deposition, is a process that uses a torch to coat an object with a protective material by charging the torch with fuel and aiming a metal alloy at the surface of the to-be-coated object. The torch emits an arc of very hot plasma that vaporizes and deposits the metal alloy on the object’s surface.
After spraying, heating the object hardens the coating and cools it down. Thermal spraying is a very versatile process that coats various materials. Thermal spraying is a very old and proven process that uses thermal energy to deposit a coating on a substrate.
The process deposits metals, ceramics, polymers, and glass into several useful coatings. We also know thermal spraying as flame spraying, plasma spraying, or plasma deposition.
The Thermal Spraying Process
They must prepare the product’s surface before the thermal spraying process begins. During the pre-treatment stage, the workpiece is prepared for coating in several ways, depending on the product. For example, if the product is a metal, it might be sandblasted or chemically treated.
Meanwhile, if it’s a plastic product, it might be cleaned and degreased. The workpiece is prepared and sent through a thermal spraying machine comprising a rotating drum by applying the coating. They heat the drum to a high temperature (typically between 500-1200 °F), causing the metal to form a small crust and break apart, which allows the resin to penetrate it.
Preheating and Pre-Treatment
Preheating the metal to temperatures between 250-350 °F before applying the coating softens it and making pliable, allowing the coating to penetrate the metal more easily. Depending on the metal, there are several ways to pre-treat the metal’s surface for the coating. A common pre-treatment process uses an abrasive material like sandpaper or an electrochemical etching solution.
Techs spray a heated coating—a combination of paint and resin—on the pre-treated metal surface during the coating. The resin has a low viscosity at room temperature but becomes very thick and viscous at high temperatures, meaning it doesn’t run or drip off the product’s surface as it cools down.
At the end of the coating process, the product cools down, helping the coating to cool down slowly and adhere to the product’s surface. After removing the product from the machine, techs scrap the excess coating off. The spraying process ends with an inspection, repeating the process if there’s damage.
Thermal spraying is a cost-effective way to coat metal parts. The process uses a thermal energy source, such as an electric arc or a torch, to coat the surface of the metal parts with a layer of protective material and improve corrosion resistance, hardness, and other properties.
Thermal spraying is used to coat a variety of different materials, such as metals, ceramics, polymers, and glass. Some benefits of thermal spraying include:
- Better quality coating: The high temperatures during the coating process ensure the coating completely covers the product, reducing the risk of defects, such as pinholes.
- Faster coating process: It has a short turnaround time, so they complete their products in a shorter time.
- Cost-Effective: It is efficient and cost-effective because it uses less paint than traditional coating methods, such as brushing and spraying.
- Environment-friendly: It produces less waste than other methods and does not require the use of harmful chemicals.
- Low energy consumption: It uses less energy than other coating methods.
- Adaptability: The thermal spraying process suits many products, including metal, plastics, wood, and concrete, but is common for coating metal, including steel, aluminum, copper, and stainless steel.
Thermal Spray Materials
Several materials can be thermally sprayed to form protective coatings. The materials include metals, ceramics, polymers, and glass. Thermal spraying is used to coat a wide range of different materials. Below are some of the most common materials used.
- Metals: companies widely use metallic materials to form protective coatings on various parts. The materials used include stainless steel, nickel, cobalt, and iron.
- Ceramics: Ceramic coatings are protective coatings that are used for wear and corrosion resistance. Some ceramic materials used include aluminum oxide, silicon carbide, and silicon nitride.
- Polymers: Polymers are a diverse group of materials that include plastics, rubbers, and other synthetic materials.
- Glass: Companies use glass materials in thermal spraying for their optical clarity.
Thermal Spraying Limitations
Although thermal spraying is a proven and reliable process, it has some limitations. Thermal spraying is not suitable for:
- All Materials: Materials such as wood and fabrics have limited thermal stability.
- Thick Parts: It’s unsuitable for thick parts with a large surface area. Thick parts have a high heat capacity and are difficult to be heated using a thermal energy source.
- High-Precision Parts: It’s not suitable for parts that require high precision.
- Highly Porous Materials: it’s not suitable for porous materials because it doesn’t cover the entire surface.
Thermal spraying is a proven and reliable process that uses thermal energy to deposit a layer of protective material on the surface of a metal part. The process uses a thermal energy source, such as an electric arc or a torch, to coat the part’s surface with a layer of protective material and improve corrosion resistance, hardness, and other properties.
Several materials can be thermally sprayed to form protective coatings, including metals, ceramics, polymers, and glass. Thermal spraying is a versatile process that coats a range of different materials.
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