The mil profile chart for aluminum oxide grit blasting helps one understand how different grit sizes affect the surface roughness or texture. They guide users in choosing the right abrasive for the task.
The Role of Aluminum Oxide in Surface Preparation
Aluminum oxide is well known for its dependability and accuracy. It has a focus that goes beyond just cleaning. It ensures the surface is textured precisely for optimal results in later stages, such as coating application or adhesion processes.
How Grit Size Impacts Surface Texture
Every grain size molds the surface in its own individual manner. Aluminum oxide is the top choice for abrasives due to its ability to produce precise and uniform textures. Texture plays an important role in optimal coating adhesion. The variety of grit sizes ranges from harsh coarse grits that deeply etch a surface to softer grits that produce a smoother, more polished surface.
The Importance of Profile Roughness (Mils)
When discussing mils, we are talking about the tiny ridges and depressions created on the surface of the material. Mils, measured in thousandths of an inch, provide insight into the extent of the surface texture. A higher mil profile means more surface roughness, which is essential for applications requiring strong adhesion. A lower mil profile is suited for finer applications, where a sleek, smooth finish is preferred but still with enough texture to allow for a solid bond.
The Science Behind Aluminum Oxide Grit Blasting
The aluminum oxide particles under pressure will blast against the material and chip away microscopic bits. They leave behind a trail of roughened surfaces. The mil profile chart, then, becomes your map to guide you through the ideal grit size for the task at hand.
Versatility of Aluminum Oxide Abrasive
This abrasive is not just for heavy-duty jobs; it’s versatile enough for fine applications as well. From coarse, thick layers of surface preparation to subtle texturing, aluminum oxide grit blasting can do it all.
Below is a generalized chart that finds use in aluminum oxide grit blasting:
| Grit Size | Typical Profile (mils) | Application |
| 24–36 | 3.0 – 5.0 | Heavy-duty applications, removal of thick coatings, creating deep anchor patterns for industrial-grade coatings. |
| 36–60 | 2.5 – 4.0 | Moderate coating removal, creating profiles for thick epoxies or urethanes. |
| 60–80 | 1.5 – 3.0 | Light coatings removal, surface preparation for moderate coatings, often used on steel and aluminum surfaces. |
| 80–120 | 0.8 – 2.0 | Fine profile for thin coatings, primers, and sealants; ideal for smoother finishes. |
| 120–220 | 0.5 – 1.0 | Very fine finishing; used for delicate surfaces or minimal profiling before thin films or lacquers. |
Notes:
- Profile Depth (mils): Refers to the depth of the peaks and valleys on the blasted surface. Measured in thousandths of an inch (mils).
- Factors Influencing Profile:
- Blasting Pressure: Higher pressure creates deeper profiles.
- Nozzle Angle and Distance: Adjusting the angle or distance affects the uniformity and depth of the profile.
- Material Hardness: Softer substrates (like aluminum) may achieve lower profiles than steel.
- Surface Preparation Standards: Aluminum oxide grit blasting can achieve various standards, including SP-6 (Commercial Blast) or SP-10 (Near-White Metal Blast), depending on the application.
- Selection of Grit Size: Always consider the coating thickness or surface treatment to ensure the correct grit size is used for optimal adhesion.
Quite some time ago, we posted a blog about Anchor Profile. This post explained what that is and why it is important.
The picture above clearly demonstrates the differences in anchor or etch profile using different mesh sizes of Aluminum Oxide Grit. All of these coupons are aluminum metal.
The top left was blasted with a 36 Mesh grade. This produces a rough looking and rough feeling surface finish. While all these blasted parts will look like sharp peaks and low valleys on the micro scale, on this coupon you can see that with just a simple 10x jewelry lens.
The upper right was etched with 120 Mesh. While you can still see some etching on this example, the surface feels much smoother and more uniform.
While still etched, the bottom example which was blasted with 220 Mesh has a very uniform, frosted finish. This is a finish often seen on frosted glasses, signs, and windows.
Selecting the proper grade of abrasive media is important to ensure you get the proper surface profile based on either next steps, such as a coating, or simply just an aesthetic finish.
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