The Guide to Sheet Metal Fabrication Finishes
Bended, plated, galvanised, or something else? See which finish is best for your sheet metal fabrication project.
How do you know which finish is best for your sheet metal fabrication project? Various surface finishing options and processes are available to enhance the appearance, durability, mechanical properties, and functionality of a wide range of sheet metal components and metal surfaces.
Surface finishing is a critical step in the manufacturing process, involving various finishing processes to achieve the desired surface finish for sheet metal components.
The decision on which sheet metal finishing process to use depends on your project requirements, with factors such as aesthetics, environmental exposure, and intended use playing significant roles. The sheet metal finishing process can enhance durability, improve mechanical properties, and modify the part’s surface for specific applications such as industrial equipment, automotive components, and precision instruments.
This guide examines some of the most popular surface finishes used in sheet metal fabrication. Surface finishes such as matte finish, smooth finish, and wear-resistant coatings are selected based on the requirements of the sheet metal surface and the intended use of the mechanical parts.
Examples include metal plating, powder-coated finishes, and organic coatings, which can improve both appearance and functional qualities, including electrical conductivity. Non-woven abrasive materials are sometimes used to achieve specific surface textures, and oxide layers, such as anodic oxide, can be formed through electrochemical processes involving electric current and metal ions.
Protective and decorative finishes can also be applied to the substrate surface, and dry powder is used in powder coating, which is an alternative to traditional liquid paint. Sacrificial metal coatings, such as zinc, provide corrosion resistance, and surface roughness is an important quality metric for metal surfaces.
Bead blasting is another finishing process where glass beads or tiny beads are propelled by compressed air to create a uniform finish, and passivation removes free iron to improve corrosion resistance.
Understanding Sheet Metal Finishes
Sheet metal finishes are crucial aspects of the manufacturing process, as they can significantly impact a part’s appearance, performance, and lifespan.
A sheet metal finish is a surface treatment or coating applied to a sheet metal part to enhance its properties, such as corrosion resistance, durability, and aesthetics. There are various types of sheet metal finishes, each with unique characteristics, advantages, and disadvantages. Understanding the different types of sheet metal finishes is essential to selecting the right one for a specific application.
Adding a surface finish to sheet metal parts can provide numerous benefits, including:
Improved Corrosion Resistance: A surface finish can protect the sheet metal part from corrosive environmental elements, extending its lifespan.
Enhanced Aesthetics: A surface finish can improve the appearance of a sheet metal part, making it more visually appealing.
Increased Durability: A surface finish can provide protection against physical damage, such as scratches and abrasions.
Improved Functionality: A surface finish can impart certain physical properties on a sheet metal part, such as conductivity or reflectivity.
Surface Preparation for Finishing
Surface preparation is a critical step in the sheet metal finishing process. It involves cleaning and preparing the surface of the sheet metal part to ensure a strong bond between the part and the finish. Common surface preparation techniques include deburring, grinding, sanding, and polishing.
The surface preparation method will depend on the type of finish being applied and the desired outcome.
Bending
As a forming operation, bending shapes the metal without removing any material. The process induces a variety of bends, including V-bends, U-bends, and channel bends. Excessive bending can lead to work hardening, possibly resulting in cracks.
Bending is a standard process in sheet metal fabrication that serves a functional purpose and can contribute to the part’s aesthetic appeal. The process is versatile and allows you to create complex geometries that would otherwise be challenging.
When to use this: Use bending when your project involves creating intricate, angular designs. But remember, the complexity of your design may influence the cost and time required for fabrication.
Brushed
Brushing is an excellent choice if you’re looking for a satin-like finish. The process uses a series of abrasive belts or brushes to create a unidirectional texture on the metal surface, effectively reducing surface defects and enhancing aesthetic appeal.
Aside from aesthetics, brushing helps hide fingerprints and minor scratches that may occur during the product’s lifespan. However, this process offers no significant protective layer against corrosion or rust.
When to use this: When the visual look of the part is essential.
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Painted
Painting your fabricated sheet metal part can dramatically improve its visual appeal. It allows for almost unlimited colour choices and is an added protective layer against corrosion, mainly used with primers. High-quality industrial paints can provide a durable surface finish that withstands extreme conditions, including high temperatures, UV exposure, and moisture.
Unlike powder coating, which uses a dry powder, traditional liquid paint is applied as a liquid suspension and typically uses solvents, making powder coating a more environmentally friendly and durable option.
When to use this: Consider painting when you want a wide colour selection and an additional protective layer. Organic coatings can also be applied over painted surfaces to enhance further the surface finish and longevity of sheet metal parts. However, complex geometries may complicate the painting process and affect the final result.
Galvanized
If you’re concerned about corrosion, galvanization is an excellent option. The process involves applying a protective zinc coating to prevent rust. The zinc acts as a sacrificial metal, corroding in place of the underlying substrate surface to protect it from damage. Additionally, the zinc forms an oxide layer on the sheet metal surface, further enhancing its corrosion resistance. It’s prevalent for outdoor applications, where the elements pose a significant risk of corrosion.
Galvanised finishes are less versatile regarding aesthetics, as the zinc coating typically gives a dull grey appearance.
When to use this: The protection it offers makes it an excellent choice for pieces that will be exposed to harsh environments.
Plated
Plating involves depositing a metal coating on the sheet metal part. Metal plating is an electrochemical process that uses electric current to deposit metal ions onto the surface of the sheet metal part. Certain plating processes, such as anodising, can create an anodic oxide layer, which enhances corrosion resistance and wear-resistant properties. Plating can also improve the mechanical properties and surface finish of mechanical parts.
Passivation is a related finishing process that removes free iron from the surface to further enhance corrosion resistance. It can serve functional and aesthetic purposes, enhancing corrosion resistance, reducing friction, improving paint adhesion, altering conductivity, and providing a decorative shine.
When to use this: Consider the plated finish to enhance specific properties of your sheet metal part. The plating material, such as gold, silver, nickel, and chrome, has a significant impact on the result. However, the process can become expensive depending on the materials used.
Choosing the Right Finish
The right finish can greatly enhance your part’s appearance, durability, and functionality, so choose wisely.
Whether you need a brushed, painted, galvanized, plated finish or complex bending operations, MakerVerse is here to help. Our experts can help you determine the most appropriate finishing process.
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