The aluminum extrusion industry has seen a lot of changes over the past few years. There are more and more companies using aluminum, including those who never used it before, all because there is a demand for this type of product.
Aluminum extrusions can be produced in many ways – from cutting to bending – and each process will give you a slightly different type of result. There are also many finishes available that will enhance the way your work looks when finished. In this blog post we’ll go through eight types of aluminum finishes that stand out among others as being particularly popular with customers today.
What are aluminum extrusion profiles?
Aluminum extrusions come in many different shapes and sizes, they are made by pushing aluminum bars through extrusion dies on the extruder to acquire the required shapes. The most recognizable aluminum profiles are standard profiles such as U-channels, round tubes and square tubes, they are often used for construction and structure applications. Other popular aluminum profiles include flat bar, L-channel, H-channel, I-beam, T-bar and trim. There is either hot rolled extrusion or cold rolled extrusion. Hot rolling results in a longer grain structure that is stronger than extrusion that has been cold rolled. Extrusions are chosen based on their strength characteristics and cost.
Why anodized finish is commonly applied on aluminum extrusions?
One of the most popular finishes for aluminum extrusions is anodizing. Anodized aluminum has several benefits. It helps protect your product from scratches and corrosion, it can be applied in many colors, and it comes with functional properties too. Anodizing is available in both clear and colored versions.
Most aluminum extrusions are anodized to protect them from corrosion. The porous structure of the anodic film acts as a barrier between your product and oxygen in water, creating an environment where corrosion is less likely to occur.
Anodizing can be done in many different colors, this gives you the ability to change the color of your product without adding another process. This is particularly useful for companies who want to use different colors in different designs, or perhaps when they update their logo and need a new color scheme that matches their look and feel.
Color can also be used as a form of coding. You could apply one color to indicate standard parts, and another color to signify the change in spec or size.
Color coding also helps improve safety. When workers can see that there's a difference in part type by the color, it will make their job easier. Also, different colors might be required for environmental reasons (e.g., red is often used at customer sites to indicate fire equipment).
Anodizing not only protects your product, but it can also be used to achieve other functional properties too. One classic example is that the porous structure of the anodic film allows for dielectric properties to be achieved, meaning your product will interact better with electrical components. The pores in the anodic coating are so small that they cannot be seen with the naked eye.
Dielectric strength is improved by an additional layer of clear varnish that can be painted onto your aluminum extrusion after it has been anodized. Clear varnish protects the porous structure of the anodic film and prevents contaminants like dust, dirt, oils, and other elements from getting under the anodic coating and causing corrosion.
Types of Several Finishes for Aluminum Extrusions
Below are list of eight types of surface finishes that enhance the appearance and properties of aluminum extrusions.
- Mill Finish
Mill finish is the natural finish that aluminum extrusions are made. It remains raw extrusions even after secondary machining such as cutting, bending, drilling, pressing and welding. In some applications there is no special requirement on finish for the extrusions, the mill finish can be the most economic finish that people choose to reduce the cost on their projects.
- Mechanical Finish
Mechanical finishes are done via mechanical processes, such as brushing, glass bead blasting, milling, grinding and embossing. These finishes provide a unique surface pattern on the aluminum extrusion. The pattern will either be cut into the metal, or it will be stamped onto the surface. Patterns are created by cutting or etching the material with tools. They are used for functional reasons or aesthetical purposes to create patterns or designs on your product.
Pretreatment is the process by which raw materials are exposed to a chemical, heat, pressure, argon gas or other treatment to create a desired surface. The process can be used on both ferrous and non-ferrous metals. The most common use is galvanizing. It often follows hot-dip galvanization. Pretreatment may also include acid pickling, zinc electroplating and phosphatizing.
- Chemical Process
Chemical processes transform a surface by applying a chemical agent. The agent can be sprayed, dipped, or brushed onto the metal to create a specific look. It is then either air dried or baked onto the material in an oven.
Anodizing creates an anodic film on aluminum metal or alloy. The process changes the surface of the metal by oxidizing it chemically with oxygen. Anodizing increases corrosion resistance and improves adhesion for paint primers. It can create porous structures that increase dielectric strength, improve appearance, allow sealing of parts against moisture and other elements, and make the surface harder.
- Liquid paint
Liquid paint is often used to color aluminum extrusions. The surface of the metal must first be pretreated with a primer, which adheres the liquid paint better than bare metal does. Liquid paint offers good protection against corrosion and chips. It's also easy to repair if it gets scratched or scraped.
- Powder coating
Powder coating creates a more durable, long-lasting finish than liquid paint by using an electrostatic process that coats the product with fine particles of colored powder. The surface is pretreated with a base coat followed by multiple layers of clear powder until you achieve the desired color or design.
Sublimation creates a dyed finish on aluminum extrusions. It starts with an inkjet printer, which prints the design you want onto paper. The paper is then pushed into a dye tank, where it is soaked in dye under high pressure to transfer the imprinted image onto the metal. Water-based dyes are used for colors that are darker and deeper than the base aluminum material. Sublimation is used on products like computer cases, automotive accessories, home furniture and graphic designs.
Why should you consider adding aluminum finish?
Adding a finish to your aluminum extrusion will not only enhance its appearance, but it can also increase the life of your product by protecting your aluminum from elements that would corrode it. Corrosion resistance is important to consider when you are designing products that will be exposed to wet or humid climates or saltwater. Aluminum manufacturers can coat their metal with a finish that increases corrosion resistance and adhesion. A protective finish also makes it easier for secondary finishing operations, such as painting, or powder coating can be applied to aluminum extrusions.
Optimal benefits of aluminum extrusions faced with the choices for anodizing, liquid paint, powder coating and sublimation finishes? Each type of aluminum finish has its own set of benefits and limitations, as well as unique uses. Consider your product design needs carefully to determine which aluminum finish can make the most beneficial impact on your final product.
How to choose right finish for your aluminum extrusion?
You should consider the following factors to help you choose an aluminum finish that best fits your product.
Aluminum alloy make sure you select a finish that is compatible with the alloy of aluminum that will be used in your extrusion. A wide variety of finishes are available for various kinds of alloys, so it's easy to find one that matches your aluminum. For example, liquid paint has been used on aircraft parts for years because the dark finish provides a high degree of antioxidative protection to keep it from being corroded by exposure to water vapor and other environmental factors.
Durability different finishes provide different levels of durability. Liquid paint provides a more durable finish than powder coating does, although not as long lasting as anodizing or sublimation. Powder coating is a popular choice because it's not only durable, but it also offers additional protection against corrosion and chips compared to liquid paint.
Corrosion resistance liquid paint provides the best corrosion resistance of any finish for aluminum parts. Anodizing is close behind, followed by powder coating. Sublimation is not as good at corrosion resistance, but the right kind of dye can provide effective protection against corrosion.
Scratch and Chip Resistance
Scratch and chip resistance powder coating offers a durable scratch and chip resistant finish. Liquid paint tends to scratch more easily than powder finishes do, so it's best used for aluminum extrusions that won't be scratched or handled roughly.
Cost some finishes are more expensive than others, depending on the aluminum alloy you're getting it for, the quality of finish and any extra metal plating required. Anodizing is typically the most expensive, while powder coating falls in the middle, followed by liquid paint and sublimation which are both cheaper options.
Aluminum finish is an important consideration to make when you are designing your product. Your choice of aluminum finish determines the durability, corrosion resistance and other factors that impact how well your metal will hold up over time. These finishes also affect cost because they can require additional materials or processes to apply them properly. Make sure you consider what type of finishing process best suits the needs of your design before finalizing a decision on which one would be right for it.