In the world of metal fabrication, many processes require high precision. These processes often involve expensive materials, and any time an operator handles something at a high cost, it’s important to have safeguards in place to prevent costly mistakes or damaged property.
Anodizing is one such safeguard. Often used on aluminum surfaces to create corrosion-resistant layers, anodizing creates a protective layer, helping mitigate natural degradation from oxidation or other environmental factors. Anodizing can be as simple as dipping the surface in an acidic solution or as complicated as using a specific voltage and current combination for one second at a time for up to several hours.
We’ll explore exactly what anodizing is, its common uses in the metal fabrication industry, and some helpful best practices when working with it yourself!
What is Anodizing?
Anodizing is a process that creates a corrosion-resistant and dye-able metal surface on aluminum, copper, and other metals. It’s used for everything from making drinking fountains to aircraft frames, corrosion-resistant cookware, and everything in between. Anodized coatings have many applications because anodizing provides aluminum with protective properties.
Here is a three-minute video illustrating the anodizing process.
Anodized aluminum has various properties depending on the type of anodizing process used. It increases resistance to chemicals and natural substances that would otherwise damage or corrode the surface of the aluminum. There are five main types of anodizing: Type 1, Type 2, Type 3, Type 4, and Hard Anodizing.
Types of Anodizing
Anodizing immerses an aluminum or aluminum alloy substrate in an electrolyte solution and applies voltage. The voltage causes the aluminum to oxidize and changes the surface color of the aluminum to green or black, where the current is most concentrated. There are five types of anodizing:
Anodizing is a coating used on aluminum or aluminum alloys, creating a protective barrier on the aluminum surface. It looks like a dull green or black color because it is a porous structure. The chemical changes during the anodization process create an oxide coating with multiple layers. The coating is usually non-conductive and provides protection against corrosion, adhesion to other surfaces, and wear.
- Type 1 Anodizing: the most common type used for decorative finishing, corrosion protection, and wear resistance. It is hard, dense, and opaque.
- Type 2 Anodizing: Type 2 anodizing increases corrosion and wear resistance with a more porous structure than Type 1.
- Type 3 Anodizing: Used for decorative finishing, increased corrosion resistance, and electrical insulation properties.
- Type 4 Anodizing: Used for decorative finishing and corrosion resistance.
- Hard Anodizing: Increases hardness and electrical insulation properties.
Anodized Aluminum Advantages
There are six chief advantages to anodized aluminum:
Appearance: Available in a variety of colors. Anodizing can produce vibrant and attractive colors like blue, red, green, yellow, and black, created during the anodizing process. Anodized aluminum can create decorative architectural items like railings, fences, doors, and panels.
Strength: Has increased strength compared to un-anodized aluminum. Anodized aluminum’s strength is because of the dense oxide coating formed during the anodizing process.
Stiffness: Has increased stiffness compared to un-anodized aluminum. The stiffness of anodized aluminum is because of the dense oxide coating formed during the anodizing process.
Wear Resistance: Has increased wear resistance compared with un-anodized aluminum. Anodized aluminum’s wear resistance is because of the dense oxide coating formed during the anodizing process.
Chemical Resistance: Has increased resistance to many chemicals compared with unanodized aluminum. Anodized aluminum’s resistance to chemicals is because of the dense oxide coating formed during the anodizing process.
Electrical Resistance: Has increased electrical resistance compared to un-anodized aluminum. The electrical resistance of anodized aluminum is because of the porous oxide coating formed during the anodizing process.
Disadvantages of Anodized Aluminum
Here are five primary disadvantages to anodized aluminum when compared to unanodized aluminum:
Cost: It’s more expensive because of the anodizing process.
Stiffness & Hardness: The increased stiffness when compared to un-anodized aluminum causes some issues in the design of certain types of products.
Weight: Anodized aluminum is heavier because of the dense oxide coating formed during the anodizing process
Electrical Resistance: Too much electrical resistance of anodized aluminum causes issues in the design of certain types of products.
Is Anodized Aluminum Safe?
Aluminum is a highly reactive metal that can corrode in air and water. It has high specific gravity and is relatively soft. The corrosion resistance of aluminum varies depending on the surface finish. The surface finish of an anodized aluminum surface is porous, impregnated with various chemical substances, and has a high electrical resistance.
The anodized aluminum surface is highly corrosion-resistant. The anodic coating on the aluminum surface is a barrier that protects the base metal from the outside environment. Engineers use anodized aluminum in architecture, transportation, and food service because of its low cost, lightweight, strength, and durability.
How to Care for Your Anodized Metal
If exposing your anodized metal in high-traffic areas, following proper and consistent maintenance schedules ensures a longer life for your project. Care methods include:
- Use non-abrasive cleaning and cleaning products
- Cleaning non-abrasive products can clean anodized aluminum using a soft cloth or sponge to wipe off the dirt.
- Avoid harsh chemicals
- Do not use harsh chemicals like acids and alkaline cleaners; these chemicals can etch the anodized aluminum surface and remove the anodic coating.
- Avoid scratching the surface.
- Do not use scouring pads or rough sponges.
- Avoid scratching the anodic coating.
- Always keep anodized aluminum away from sharp or abrasive objects.
- Avoid scratching the electrical connections.
- Always keep anodized aluminum connectors away from sharp or abrasive objects.
When considering anodizing as a protective metal coating, you’ll find many advantages (disadvantages, too!) the process offers. However, one thing limiting its effectiveness: not all metal fabrication projects call for aluminum substrates!
However, anodized aluminum is as ubiquitous as it comes. At the end of a walk down a city block, you’ll miss more examples of anodizing then you’ll see.