Secondary Processes

What Are Secondary Machining Processes?

What Are Secondary Machining Processes?

September 6, 2023

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What Are Secondary Machining Processes?

Blog ➔ Secondary Processes

 

What Are Secondary Machining Processes?​

Depending on the type of part being manufactured, there are many steps in the process from raw material to finished part. Parts with various surface features or unique shapes often use multiple machines and machining processes. 

For example, a CNC machine might cut and form the general shape of the part. Then another machine may form threads on the parts. Then a grinder machine durburrs the part. And after that, the parts are washed and engraved.

Modern CNC machines have advanced capabilities, but they can’t do everything.

Secondary machining processes form the features that weren’t done in the initial machining of the part. This includes things like deburring, engraving, sub-assembly, and surface treatments like anodizing, heat treatment, and powder coating.

The secondary processes are less extensive than the initial machining. They’re used to add the specific final touches to the parts and components. 

Here are four examples of common secondary processes that we provide.

Engraving

Parts are engraved for a variety of reasons. One of the most common reasons is to keep track of different lot numbers and help identify parts that look similar. Engraving parts can also help identify different metal alloys since they usually look the same.

After parts are machined, we use in-house CNC engravers and laser engravers to add part numbers, lot numbers, AISI numbers, and more to parts.

Laser engravers are more accurate and can be used for smaller text, or more complex designs like a QR code. The CNC engraver will provide a more durable engraving.

Deburring

Deburring is a secondary process used to remove small imperfections from parts. Deburring isn’t always necessary, but sometimes the machining process creates small burrs on parts—especially when there are small slots, threads, or sharp edges.

During the deburring process, a spinning brush, grinding wheel, or belt is used to remove the burrs and smoothen out the part. 

A burr is a small protrusion on a part and they’re usually sharp. For certain parts, deburring is a necessary process for parts to function properly and ensure safe handling.

Sub-Assembly

Sub-assembly is a process where two or more separate parts are attached together by the manufacturer. The term “sub-assembly” refers to components that are first assembled together and then integrated into a larger assembled unit. So, a sub-assembly isn’t the final product. Some more complex parts or components are machined as separate parts to speed up the production process, and then assembled.

In some cases, the assembled parts are two different materials, like attaching a rubber o-ring to a metal part.

When sub-assembly operations are outsourced to the manufacturer, it saves time and allows the customer to scale their operations.

Surface treatments

Various things can be done to the surface of the part. This includes heat treatment, anodizing, plating, and powder coating. These are usually to add durability to the part.

Different surface treatments are used for different types of parts and use cases. Metals that are more susceptible to rust or scratches are more likely to benefit from surface treatments.

Steel parts are the most common for plating, when a thin layer of zinc, nickel, or chromium is added to the part. Many steel parts are also heat treated, which makes the steel harder and stronger, but also more brittle.

Aluminum parts are often anodized, which adds a thin layer of oxidized aluminum so that its surface is no longer reactive. The layer of oxidation offers protection from scratches and mechanical wear, as well as chemical protection from water and oxygen.

Primary vs. Secondary Machining Processes

When we talk about machining, it’s crucial to differentiate between primary and secondary processes.

Primary Machining Processes

These processes form the foundation of the machining world. 

It’s where a raw material undergoes substantial transformations to emerge as a product resembling its final form. Think of this as sculpting a rough statue out of a marble block. Here, substantial material is removed, and the basic structure of the part is established. Primary processes include operations like turning, milling, and drilling.

  • Objective: The primary goal is to form the main structure of the part. This involves turning a raw material into a component that closely resembles the final product in shape and size.
  • Techniques: These often include processes like milling, turning, and drilling, where significant material removal occurs.
  • Machinery: Primary machining typically uses machines like CNC milling machines, lathes, and drill presses.
  • Outcome: At the end of this stage, the part will have its main shape but might lack finer details, specific finishes, or refined edges.

Secondary Machining Processes

Once the basic form is established, we shift to refining and enhancing.

The secondary processes are like the final touches to the statue, where intricate details are carved, rough edges are smoothed, and the piece is polished to perfection. These operations, which include deburring, engraving, and surface treatments, are crucial for functional efficacy, aesthetics, and safety.

  • Objective: The goal here is refinement. After primary machining gives the part its general shape, secondary processes enhance its function, appearance, and specificity.
  • Techniques: These can range from deburring (removing rough edges) to engraving specific codes or information on the part. Other processes can include heat treatment or surface finishing.
  • Machinery: This could involve more specialized equipment, such as grinders, engravers, or machines for specific surface treatments.
  • Outcome: The final product, ready for use or assembly, emerges after these processes. It meets all quality standards, functional specifications, and aesthetic requirements.

Secondary processes impact on project lead times

Understanding the timing of a project, especially when lead time is critical, requires a grasp of how secondary processes fit into the overall production timeline:

Integration with Primary Processes: In some cases, secondary processes can be integrated seamlessly with primary ones. For instance, a modern CNC machine might mill a component and then immediately engrave a serial number, all in one go. This reduces additional setup and handling time.

Complexity and Specificity: The more complex or specific the secondary process, the longer it might take. For example, a simple deburring process might add minimal time, while multi-step surface treatments could extend the lead time.

Batch Processing: Some secondary processes, especially those related to finishing, might be done in batches. If your project is part of a larger batch, it could influence the lead time.

Efficiency Enhancements: Many manufacturers, aware of the potential time added by secondary processes, invest in technologies or methodologies to speed these up. For instance, automation and robotics can drastically reduce the time taken for certain secondary operations.

Feedback and Revisions: If there’s a need for adjustments after the secondary processes (maybe a logo isn’t engraved clearly), this can add to the project’s duration. However, regular quality checks reduce these delays.

While secondary processes generally increase lead times, their impact varies based on the project, the processes involved, and the manufacturer’s capabilities. It’s always good to discuss lead time expectations upfront, especially if you’re working on a tight schedule.

Spex has served as a local manufacturer since 1946. We provide a wide range of manufacturing services. If you want to learn more about our precision machining capabilities or secondary machining services, reach out to one of our team members to get a custom quote.

FAQs

Are there any materials that particularly benefit from secondary processes?

  • All materials can benefit from secondary processes depending on the application. For instance, steel parts often undergo surface treatments to prevent rust, while aluminum parts might be anodized to increase surface durability.

How do I know if my part requires secondary processes?

  • It depends on the design, application, and the desired finish of your part. If a part has sharp edges, requires specific markings, or needs additional surface treatments, it will probably require secondary processes.

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Heat Treating Aluminum Parts: Benefits and Methods

Heat Treating Aluminum Parts: Benefits and Methods

March 29, 2023

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Heat Treating Aluminum Parts: Benefits and Methods

Heat Treating Aluminum Parts

Heat treating is a process used to alter the physical and mechanical properties of metals. Aluminum is a popular material choice for many industries because it’s lightweight and corrosion resistant. Heat treating aluminum parts is a common practice to increase the strength, hardness, and ductility of the metal.

Heat treating aluminum parts involves heating the material and holding it at a specific temperature for a certain period of time. This process can achieve different results depending on the desired outcome. 

For example, heat treating can be used to soften the metal for easier machining or to harden it for increased strength and durability.

Heat treating can significantly improve the properties of the metal and make it more suitable for a variety of applications. Proper heat treatment can also extend the lifespan of the parts and reduce the risk of failure. This article will help you understand the basics of heat treating aluminum parts.

Why Heat Treat Aluminum Parts

Aluminum parts are often heat treated to improve their strength, durability, and resistance to wear and tear.

Here are some of the benefits of heat treating:

  • Improved strength: Heat treating can significantly increase the strength of aluminum parts, making them more resistant to bending and cracking. This is especially important in the aerospace, automotive, and construction industries, where parts need to withstand high stress and loads.
  • Better wear resistance: Heat treating improves the wear resistance of aluminum parts, making them less prone to damage from friction, abrasion, and corrosion. This is important in applications where parts are exposed to harsh environments, such as marine and offshore industries.
  • Enhanced machinability: Heat treating can make aluminum parts easier to machine by reducing the hardness and improving the surface finish. This saves time and manufacturing costs, and also improves the accuracy and precision of the finished parts.
  • Controlled distortion: Heat treating can also be used to control the distortion of aluminum parts, which happens due to uneven cooling or thermal stresses. By controlling the heating and cooling process, the distortion is minimized, resulting in parts that are more accurate and consistent in shape and size.

Heat Treating Process

The heat treatment process can be explained in several subsections: preparation, heating, soaking, quenching, and aging.

Preparation

Before the heat treatment process begins, the aluminum parts must be cleaned and prepped. This involves removing any surface contaminants, such as oil or grease, and ensuring that the parts are free from any defects or cracks. The parts are then placed in a furnace or heat treating oven.

Heating

Once the parts are in the furnace, they are heated to a specified temperature. The temperature and duration of the heating process will depend on the aluminum alloy and desired outcome. During the heating process, the aluminum parts will begin to soften and become more malleable.

Soaking

After the parts have been heated to the desired temperature, they’re “soaked” at that temperature for a specific amount of time. The heat penetrates the entire part and ensures that the desired properties are achieved. For smaller parts, this can take 10 minutes, and up to 12 hours for larger parts.

Quenching

After the soaking process, the parts are rapidly cooled by quenching them in a liquid or gas. This rapid cooling process is essential to lock in the desired properties and prevent the aluminum from returning to its original state.

Aging

Finally, the parts are “aged” by bringing them to a lower temperature for a specific amount of time. This aging process allows the aluminum to reach its final properties and improves its strength and hardness.

Applications of Heat Treated Aluminum Parts

Heat treating is an essential process for aluminum parts used in various industries, including aerospace, automotive, construction, and electronics. Heat treatment enhances the mechanical properties of aluminum, making the parts stronger, more durable, and resistant to wear. Here are some common applications of heat-treated aluminum parts:

Aerospace

Aluminum is commonly used in the aerospace industry for its lightweight, high strength, and corrosion resistance. Heat-treated aluminum parts are used in various aerospace applications, including:

  • Structural components such as frames, wings, and fuselage
  • Engine components such as fan blades, compressor blades, and turbine disks
  • Interior components such as seats, overhead bins, and galleys

Heat-treated aluminum parts are critical for the safety and performance of aircraft, as they must withstand extreme temperature changes, pressures, and loads.

Automotive

Aluminum is increasingly used in the automotive industry because it’s lightweight and improves fuel efficiency. Heat-treated aluminum parts are used in various automotive applications, including:

  • Engine components such as cylinder heads, pistons, and connecting rods
  • Transmission components such as housings and gears
  • Suspension components such as control arms, knuckles, and spindles

Using heat-treated aluminum parts in vehicles helps reduce weight, improve performance, and increase fuel efficiency.

Construction

Aluminum is also used in the construction industry for its lightweight, corrosion resistance, and aesthetic appeal. Heat-treated aluminum parts are used in various construction applications, including:

  • Windows, doors, and curtain walls
  • Roofing, siding, and decking
  • Structural components such as beams, columns, and trusses

Heat-treated aluminum parts in construction provide durability, strength, and design flexibility.

Overall, heat-treated aluminum parts are essential for various industries and applications, providing strength, durability, and performance. The heat treating process ensures that aluminum parts meet the required mechanical properties and standards, enhancing their reliability and value.

Heat Treated vs Anodized Aluminum

Anodizing aluminum is a different finishing process that has similar benefits to heat treating. The anodizing process creates a thin layer of oxide on the part’s exterior. The oxide layer acts as a stronger, corrosion-resistant, and visually-appealing surface.

The primary difference between heat treating and anodizing parts is how the structure changes. Heat treating changes the entire structure of the part, while anodizing only adds a layer of protection to the outside of the part.

The treatment process that you choose depends on the purpose of the part and the environment it’s being used in.

Which aluminum finish should you choose?

Your choice of finish ultimately depends on how your part and product is going to be used. Heat treating, anodizing and powder coating are both great finishing options for aluminum parts.

Heat treatment is often used for cast aluminum parts and cold rolled parts. This is ideal for increasing the strength of the parts, and benefits the entire part, rather than just treating the part’s surface. 

Anodizing is ideal if you need to add a layer of protection while maintaining tight dimensions. You’ll get excellent corrosion and wear resistance, and have an attractive metallic look without increasing the size of your part too much. Anodizing is also the better choice when your part needs to dissipate heat, or if you’ll be using any glue or primer on it.

Powder coating is the better option when you want vibrant colors and unique textures that will last. The coating will last even when exposed to the outside elements. Powder coating also offers good protection at a lower cost than anodizing.

Spex is an ISO 9001:2015 certified precision machine shop in Rochester, NY. We machine thousands of unique metal and polycarbonate parts every month for different industries around the world. Reach out to our team to see if we can help with your next project. 

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Laser Engraving vs CNC Engraving: How Should You Mark Your Metal Parts?

Laser Engraving vs CNC Engraving: How Should You Mark Your Metal Parts?

June 18, 2022

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Laser Engraving vs CNC Engraving: How Should You Mark Your Metal Parts?

Laser Engraving vs CNC Engraving

After they’re machined and cleaned, many parts are engraved or marked. Engraving is commonly used to identify the metal alloy of the part, track part lot numbers, or add specific part numbers.

For example, a stainless steel component might be engraved with:

SS303
#002

That would indicate to people that the part is 303 stainless steel, and is the second lot of parts. 

Anything can be engraved on metal parts, but it is a secondary process that happens after machining, so it adds to the manufacturing time and costs. You only want to engrave information that’s necessary.

The two most common ways to engrave metal parts are laser engraving, and CNC engraving. The same general principles apply, but they are two different machines, and mark the parts differently. In some cases, laser engraving is better, and other times CNC engraving is best.

We’ll explain how each process works, and what its recommended use cases are.

Quick comparison

The biggest difference between laser engraving and CNC engraving is the actual engraving process. They both achieve similar results. 

A laser engraver uses a high-power laser to heat and vaporize a tiny amount of material off the surface of a part. Because there’s no contact, the part generally doesn’t need to be fixed.

A CNC engraver uses a sharp cutting tool that touches the surface of the part to remove material. This process usually engraves a single part at a time, and the part is secured in a vice.

CNC Engraver | Laser Engraver

How does laser engraving work?

The first laser engraving machine was purchased over 40 years ago, in 1978. Since then, the technology has improved drastically, and laser engravers are more accessible. Laser engravers use heat to burn and permanently mark a surface. 

They can be used to create artwork on a piece of wood, glass, or metal. The machine works similarly to a CNC machine. You use a computer program to upload the image and text you want engraved, hit go, and the laser moves around, etching your design onto the surface.

Different settings can be adjusted depending on the material you’re engraving and increase or decrease the intensity of the laser marking. If you want a more prominent marking, the speed can be slowed down, so the laser burns the material for longer.

Setting up the laser engraver can take some time, and you might need to make adjustments if the marking isn’t clear enough. It can also be challenging to mark a curved or uneven surface. But, once you get the right settings right, laser engraving is a quick process. And a tray of 100+ parts can be set in the engraver to be marked simultaneously. 

Laser engraving is used for simple part numbers, and more complex engravings like a barcode or QR code.

How does CNC engraving work?

A CNC engraver setup is more like a drill press. There is a sharp, pointy cutting tool that’s dragged across the part surface to mark the surface of the part. The engraver is connected to a computer program where the marking details are entered. 

Generally, this engraving process is used specifically for hard metal parts.

The parts are held in a vice attached to the engraving table while the cutting tool moves around to mark the part or lot numbers. Unlike a laser engraver, a CNC engraver usually works on one part at a time. The engraving takes a few seconds, and then the cutting tool resets and is ready for the next part. Because the parts need to be switched out one by one, this engraving requires more human attention.

CNC engraving is commonly used in the automotive, aerospace, healthcare, and oil and gas industries. It’s used to add simple numbers to parts, and not ideal for more complex engravings.

Pros and cons of each method

These part marking processes are similar, but they both have specific pros and cons. 

Pros and cons of laser engraving

  • Laser engraving can be used on a wider variety of materials.
  • The parts being engraved don’t need to be held in a vice.
  • Laser engraving can be faster than CNC engraving, especially for large quantities of parts.
  • Laser engraving makes a clear and crisp finish even for intricate and small markings.
  • Laser engraving can wear off softer metals over time.

Pros and cons of CNC engraving

  • CNC engraving can provide a deeper, longer-lasting engraving.
  • CNC engraving provides comparatively greater material flexibility.
  • CNC engravers can offer a simpler and faster set up. 
  • CNC engravers require the parts to be more secured during the engraving.

Engraving parts is a common secondary process. Both laser engraving and CNC engraving are great ways to add important numbers and markings to your parts. This can help with inventory management and tracking parts. Reach out to our team to learn more about our secondary manufacturing operations.

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Anodizing vs Powder Coating: Choose the Best Aluminum Finish

Anodizing vs Powder Coating: Choose the Best Aluminum Finish

May 19, 2022

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Anodizing vs Powder Coating: Choose the Best Aluminum Finish

Anodizing vs Powder Coating

Aluminum is one of the most commonly used metals for precision parts. Aluminum is lightweight, strong, and easy to machine. 

Oftentimes, manufacturers use a secondary process like anodizing or add a powder coating to increase the durability of the aluminum parts. These processes also add visual appeal to the parts.

These two processes have their own pros and cons, and use cases. This post will help you decide which finish is best for your aluminum parts.

What is anodizing?

Naturally, aluminum doesn’t rust, but it does corrode over time. Over time, a thin layer of oxidation forms on the outside of aluminum. This layer provides some protection from corrosion.

Anodizing is a chemical process that increases the layer of oxidation. The parts are placed in an electrolytic solution like sulfuric acid, and an electrical current is passed through the part. The increased oxidation layer increases the resistance to wear and corrosion, increases heat dissipation, and improves glue and primer adhesion.

Anodized aluminum usually has a matte finish. Natural dyes can also be added during the anodizing process, so different colors can be added to the parts. When the parts are colored, they have a more metallic finish. The color is also added under the surface of the part, so it can’t be scratched off.

What is powder coating?

Powder coating is a dry paint process done to add a decorative and durable coating to parts. After the parts are machined, they’re sprayed with a powder that attaches to the metal. Then the parts are heated or baked in an oven to cure the powder coating.

Powder coating offers a strong layer of protection, and the amount can be adjusted to add more or less. Powder coating is a very environmentally friendly form of finishing.

You can also adjust the look and color of powder coating, making it more or less glossy, and more or less textured.

Anodizing vs. Powder Coating

Both of these finishing options provide great physical and visual benefits. They do have some key differences that make them better for specific uses. Usually a part can’t be anodized and powder coated, so it’s best to choose one or the other. 

In some cases, anodized parts can be painted, but it’s not ideal.

Anodized Powder Coating
The anodized layer can be very thin, and only slightly change the part dimensions.
It’s very difficult to obtain a thin layer of powder coating.
Offers a variety of metallic colors and smooth finishes.
Offers a wide variety of colors and various textures.
With proper recycling processes, anodizing is very environmentally friendly.
No solvents are used in the process, making it very environmentally friendly.
Anodizing provides excellent wear, scratch, and corrosion resistance.
Good corrosion resistance, but it is more subject to wear and scratches than anodizing.
Resistant to color fading as long as the dye is UV resistant and it’s sealed properly.
Very resistant to color fading, even when exposed to constant UV light.
Anodizing makes the aluminum non-conductive.
Has limited electrical conductivity compared to bare aluminum.
Anodizing can be more expensive.
Powder coating is more cost-effective.

Is anodizing or powder coating cheaper?

Powder coating parts is usually less expensive than anodizing. Both processes are cost-efficient, and the coating lasts a long time. There are many factors that impact the price of both services. The part shape and size, coating thickness, dyes, and quantity of parts are all important to consider. Because anodizing won’t scratch off like powder coating, the costs can even out over time. 

Most companies will charge a minimum for anodizing and powder coating parts.

Common uses for each finish

Because these finishes offer great protection, you’ll see them both used on most aluminum consumer goods. Aluminum is a great metal to use, but adding a finish increases the longevity of the parts.

Anodized Powder Coating
Automotive parts
Automotive parts
Aerospace parts
Appliances
Appliances
Lawn equipment
Electronics
Playgrounds
Sporting goods
Outdoor equipment and furniture
Furniture
Jewelry and artwork

Which aluminum finish should you choose?

Your choice of finish ultimately depends on how your part and product is going to be used. Anodizing and powder coating are both great finishing options for aluminum parts.

Anodizing is ideal if you need to maintain tight dimensionals. You’ll get excellent corrosion and wear resistance, and have an attractive metallic look without increasing the size of your part too much. Anodizing is also the better choice when your part needs to dissipate heat, or if you’ll be using any glue or primer on it.

Powder coating is the better option when you want vibrant colors and unique textures that will last. The coating will last even when exposed to the outside elements. Powder coating also offers good protection at a lower cost than anodizing.

Spex is an ISO 9001:2015 certified precision machine shop in Rochester, NY. We machine thousands of unique metal and polycarbonate parts every month for different industries around the world. Reach out to our team to see if we can help with your next project. 

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What is Plated Steel?

What is Plated Steel?

November 3, 2021

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What is Plated Steel?

What is plated steel

Plating metal has been done for hundreds of years. Plating is done for a number of reasons, and it’s an essential part of modern industries. Plating steel parts allows us to use them in a much wider variety of industries and use cases.

Plating steel with Zinc or Chromium has similar benefits to anodizing aluminum, and the process can be similar.

In this article, we’ll share the benefits of plating steel, different methods we use to plate steel parts, and more.

Benefits of plating steel

Steel is the most commonly used metal in the world. But on its own, steel has some significant disadvantages. The main issue with steel is that it’s subject to rust and corrosion when it’s exposed to moisture. 

Plating steel parts reduces corrosion, increases the hardness, improve wearability, reduces friction, and can alter conductivity. There are a few different types of plating, and they each have unique pros and cons. 

Increased resistance

One of the primary benefits of plating steel is the increased resistance to wear. Steel is a hard metal with high yield and tensile strength, but it’s more subject to corrosion. When steel parts are plated with a protective material, the longevity and durability increases. 

Metal plating protects steel parts from chemical damage, friction, and corrosion.

Appearance

Another benefit of plated steel is a better aesthetic appearance. After machining the steel parts, they can be electroplated, or plated with zinc or chromium. The plating process reduces minor imperfections and scratches, and prevents future rust. Plating steel also makes parts easier to clean making routine maintenance faster and easier.

Zinc Plated Steel

Zinc is one of the most common materials used in plating processes. Zinc plating, also called electro-galvanizing, involves adding a thin layer of zinc to the outside of a steel part. Zinc plating can still rust and doesn’t prevent all corrosion, but it rusts at 1/30th the rate of steel.

The parts are immersed in a chemical solution of zinc and an electrical current is used to apply the layer of zinc. Zinc plating usually adds a thickness between 5μm and 25μm (0.005mm-0.025mm).

There’s also a process called cold galvanizing. Essentially, this process adds a layer of zinc-rich primer. This does offer some protection against rusting, but as soon as it’s scratched, moisture can reach the underlying steel causing rust and corrosion.

Chrome plated steel

Chrome plating (also called chromium plating) adds a hard and shiny layer of nickel to steel parts. This technique uses electroplating to add chromium to the outside of the steel. 

The layer of chromium is used to add aesthetic appeal, reduce corrosion, increase the hardness of the parts, and make cleaning easier. If the plating is done for pure aesthetic reasons, a cheaper imitator of chrome is used.

Most of the car parts that are referred to as “chrome”, are steel parts that have been plated several times. This ensures that the chrome plating can withstand temperature changes and weather that a car is subject to. Triple plating is the most durable process. This plates the steel with copper and then nickel before the chromium plating.

Electroless Nickel plating

Electroless nickel plating, also known as enickel or NiP, offers many advantages. This process results in a more uniform layer over more complex part surfaces. This plating is commonly used for ferrous metals steel, and offers better corrosion resistance compared to electroplating.

Electroless Nickel plating is commonly used in the aerospace and automotive industries, but the cost of plating is usually higher than electroplating.

Galvanized steel

Galvanizing is another plating process that adds a layer of zinc to the steel parts. This is typically done by hot galvanizing, where the parts are dipped into a bath of molten hot zinc.

The hot dip leaves a thicker coating of zinc compared to electro-galvanising. This plating offers better durability, but it’s not suitable for all parts. Smaller nuts, bolts, and threaded parts need a thinner layer of zinc to maintain their original features and function. The protection provided by hot-dip galvanizing is insufficient for products that will be constantly exposed to corrosive materials such as acids, including acid rain and outdoor uses.

This graphic compares the amount of material added to steel parts using different plating processes:

Comparison of Zinc Galvanization

Plated Steel vs Stainless Steel

Is plating better than stainless steel?

Chrome plating looks similar to stainless steel, but how do they compare side-by-side? 

Stainless steel is an alloy mix of chromium and nickel; it needs to contain at least 10.5% chromium to be considered stainless steel. Stainless steel is also resistant to corrosion and staining. It’s low maintenance and very durable.

Stainless steel is more durable than chrome plating, but it’s also heavier and more expensive. 

Plated steel may be able to replace stainless steel in certain applications, but it depends on what the part is being used for. The resistance level of plated steel mostly depends on the thickness of the plating, and the environment the part is being used in. 

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Anodizing Aluminum

Anodizing Aluminum

November 1, 2021

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What is Anodized Aluminum?

What is Anodized Aluminum

The use of anodized finishes has helped make aluminum one of the most commonly used materials in the world today. You’ll find anodized aluminum in thousands of consumer, commercial, and industrial products.

Aluminum is used because it’s lightweight, resistant to corrosion, and easily malleable. Aluminum can be cast into any shape, and complex part features can be easily machined. 

When aluminum is anodized, it maintains the lightweight properties and machinability while adding strength and durability. Aluminum is the most common metal that’s anodized, although other nonferrous metals such as magnesium and titanium can be anodized.

In this article, we’ll explain how the anodizing process works, as well as the benefits and uses of anodized aluminum. 

How is aluminum anodized?

The main reason aluminum is anodized is to protect it from corrosion and wear. The process also allows manufacturers to add a layer of color to the aluminum, which enhances its aesthetic value even as it protects the metal.

Anodizing aluminum is an electrochemical process, which simply means it involves a mixture electricity and chemical reactions. The process actually changes the aluminum rather than adding a layer of paint or protective spray that wears off. Because it is integrated into the metal rather than just applied to the surface, it cannot peel or chip.

Before the aluminum is anodized, the parts are throughly cleaned and rinsed. Then the parts are immersed in a conductive solution with lots of positive and negative ions floating around. Then, a positive electric charge is applied to the aluminum, making it the “anode”, while a negative charge is applied to plates suspended in the solution. The electric current causes positive ions to be attracted to the negative plates, and negative ions to attach to the aluminum part.

When the part is dipped in the acid bath, the high electrical currents that cause surface oxides to “grow”.  This oxide growth is called anodize. 

The anodizing process adds a layer of oxidized aluminum so that its surface is no longer reactive. Anodized aluminum is still very conductive, but the surface is much harder than un-anodized aluminum. The layer of oxidation offers mechanical protection, ie. protection from scratches and mechanical wear, as well as chemical protection from water and oxygen. 

Here is a graphic of what anodized aluminum looks like:

Anodized Aluminum

Does anodizing wear off?

Anodizing provides a thin aluminum oxide layer, which will deteriorate over time. Depending on the thickness and quality of the anodization, the surface will last between 10-20 years. 

Because of its longevity, anodizing is one of the best ways to improve the durability of aluminum. The anodized layer can be removed in a Sodium Hydroxide acid wash. You could also remove the anodizing with rough sandpaper if you want to get back to the unfinished aluminum. 

Does anodizing add thickness?

When aluminum is anodized it adds a small amount of material to the part. In the graphic below, you can see how some of the thickness of the coating is ingress into the material and some of the thickness is added to the material. For most alloys, the anodized coating is approximately 50% ingressed and 50% growth.

Anodized Aluminum

How much thickness is added? Anodized coating thickness may vary depending on the aluminum alloy and the specific anodizing process.

Typical coating thicknesses are as follows:

  • Up to 5µm for chromic acid anodizing
  • 5-15µm for clear (natural) sulphuric acid anodizing
  • 10-25µm for dyed (colored) sulphuric acid anodizing
  • 20-70µm for hard anodizing, with thicknesses up to 100µm on some alloys.
100µm is 0.1 millimeters, so the added thickness would be unnoticeable to the human eye. And when you’re ordering parts, the anodization process would be factored into the dimensions. 

Types of anodizing

There are a few different types of anodizing that each have different uses and purposes. The end result of each process will look similar. The main differences will be the thickness of the oxidation layer.

Chromic acid anodizing

Chromic acid was used in the early 1900s to anodize parts. The process adds a thin layer of oxidation to the parts.

Sulfuric acid anodizing

The Sulfuric acid anodizing process looks the same as the Chromic acid, other than a different acid is used. Sulfuric acid adds a thicker layer of oxidation and is more suitable for adding color, so it’s used more often than Chromic acid.

Hard anodizing

Hard anodizing also uses a sulfuric acid, but produces a thicker anodized layer that is also suitable for adding color.

Should every part be anodized?

Aluminum doesn’t always need to be anodized, but we find that in most cases it’s the best choice. The choice to anodize parts depends largely on the environment the part will be in. The cost of anodizing aluminum is similar to painting the parts, and anodizing offers greater durability and long-lasting color. 

Spex offers anodizing as an additional service when you order precision aluminum parts. Reach out to our team to learn more about our precision machining services, and secondary manufacturing services.

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