Laser engraving anodized aluminum from kitchen utensils and window frames to beer kegs and industrial applications like airplane parts, Aluminum is one of the commonest metals in both domestic and industrial applications. Some of its unique selling points include corrosion resistance, reflectivity, impermeability, electrical and thermal conductivity, as well as its lightweight nature.
There are two main types of aluminum – standard aluminum and anodized aluminum. Anodized aluminum has an extra oxide coat which makes it a very good material for laser engraving projects.
What is anodized aluminum?
The term “anodizing” refers to an electrochemical process that adds an oxide layer on aluminum. This is achieved by dipping the aluminum into an acid electrolyte solution and then passing an electric current through it.
A cathode is mounted to the anodizing while the standard aluminum acts as the anode. During this process, oxygen ions are released from the acid solution to combine with atoms located at the surface of the aluminum. The result is the formation of an oxide layer that integrates itself onto the existing material through a strong molecular compound.
Benefits of anodized aluminum
Anodization has made aluminum a widely used and respected material in the production of commercial, consumer, and industrial products. This is because of the following reasons:
- Extra protection: compared to its standard counterpart, anodized aluminum is less likely to rust when exposed to corrosion-inhibiting elements (salt, air, and moisture). The extra layer of oxide offers a higher level of corrosion resistance.
- Integrity: apart from corrosion-resistance, anodized aluminum cannot chip, peel, blister, or flake.
- UV resistance: anodizing finishes have better resistance to sunlight.
- Low-maintenance: it is relatively cheaper to maintain anodized aluminum over the years since it can be renewed by cleaning. The oxide layer can be effortlessly restored after long years of use.
- Decorative properties: anodized aluminum has a deep, rich metallic appearance that makes it highly decorative. The anodizing coating is translucent meaning the metal underneath is still visible through it.
- Increased adhesion: the oxide layer has deeper pores that offer greater adhesion. Primers, adhesives, and other liquids easily flow through the pores.
- Better lubrication: in addition to increased adhesion, the deep pores of anodized aluminum allow for better retention of lubricant film or oil.
- Eco-friendliness: anodized aluminum produces few (if any) harmful substances to the environment.
- Dyeing and pre-treatments: anodization lends aluminum to a number of processes. This includes dyeing and pre-treatments done to enhance the material further.
Laser engraving anodized aluminum
Laser engraving anodized aluminum results in high contrast patterns and this makes it ideal for making plaques, signs, machine tags, barcoding, and QR applications. A laser can be used to create nice, bright engravings.
Both fiber and CO2 lasers are effective in marking anodized aluminum. The best thing about laser engraving is that the surface is not chipped during the process. Basically, the laser beam bleaches the dye and uncovers the white hue of the anodized layer.
During the engraving process, the protective anodic layer (usually ranging between 8-30um) is partially removed. The color contrast is a result of the laser engraving and that of the anodized aluminum.
Some lasers can mark different grey to black shades but in most cases, the engravings are nice and bright. The process of laser engraving anodized aluminum in black utilizes short pulse durations that don’t create any damage on the surface of the material. This is because the anodized coating is not removed but rather repainted. The results look somewhat like those of annealing colors on a stainless steel material.
Anodized aluminum can be laser engraved to create beautiful and permanent marks on promotional tags and signs. You can use your laser to engrave your company’s brand or logo on promotional items such as bottle openers, pens, and key chains.
What is the best laser engraver for anodized aluminum?
Laser engraving on anodized aluminum is a tricky job that requires an equally powerful engraver. Most projects utilize 60-watt CO2 laser or 30W Fiber Laser. However, with slower speeds and more laser passes, a 10-watt diode laser will get the job done. That said, it is a good idea to use a laser engraver that handles aluminum well.
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Types of anodized aluminum for laser engraving
The exact type of anodized aluminum used will influence exactly how the engraving is done. This includes influencing parameters such as speed, exposure time, and aftercare. Here are the three main types of anodized aluminum that can be used for laser engraving projects.
- Type I and II anodized aluminum
Typically, Type 1 and Type II anodized layers are the easiest materials to engrave on. These layers are very thin (less than 1/1000inch) and can be engraved with minimal contact time and energy. The ablation process alters the surface of the parent material rather than breaking the molecular bond between the aluminum and anodized layers.
This leads to scattering of light that produces a color that falls somewhere between clean and white. To create an even better contrast with the engraved section, a dark-colored dye can be used on the anodized layer.
- Type III anodized aluminum
When working with a thicker anodized coating (called type III layer), you will need a laser with a higher power output. You can achieve the same results with a less powerful laser as long as you increase the number of the passes or elongate the exposure time.
The first pass, also referred to as the damage pass, gets rid of the anodized layer. The second one, cleanup pass, brightens up the engraved section and removes the residue left behind after the damage pass.
- Clear anodized aluminum
For a clear coating, increasing the exposure time and power output will deliver a dark engraving. Later, a metal finishing solution can be added to the material to concentrate the color on the engraved area.
The solution could be Birchwood Casey, Auma Black, and others. If you can’t get your hands on this solution, focus on changing your laser parameters to enable you to mark varied shades from grey to black on the material.
Why use a laser to engrave aluminum
Creating marks on metals can be achieved through various techniques. However, laser engraving has some distinct advantages. Here are some of the benefits of laser engraving aluminum.
- Permanent marks
laser engraving on aluminum delivers marks that can withstand mechanical stress, repeated abrasion, UV exposure, and temperature stress. This is a very important feature if you are creating marks to be used for quality control and traceability as in the case of aircraft and automotive parts. This also holds true if you are looking to create promotional items that will stand the test of time.
laser engraving doesn’t use chemicals and inks. This means zero handling and waste disposal issues.
with zero consumables, laser engraving aluminum is a cost-effective marking option. Additionally, lasers require less maintenance and parts replacement which means more savings.
laser engraving is essentially a non-contact technology making it a very flexible process. You can use it to create myriad shapes and sizes. Since you don’t need to clamp the part before engraving, you can save a lot of time working with your laser.
- Maintains the initial properties of aluminum
laser engraving doesn’t strip the parent material of its protective anodized layer. This means that its corrosive resistant properties are kept intact unlike other technologies such as salt spray testing which gets rid of the layer.
- High resolution images
With a laser engraver, you can engrave images and designs of up to 1200 dpi.
Anodized aluminum is a versatile material with awesome properties. Engraving on it is an equally fun and versatile process. The trick is in knowing the type of material you are working with and how to adjust your laser parameters accordingly. As long as you have good material and a good laser engraver, you should get good results.