BRIGHTSTAR
PROTOTYPE CNC CO., LTD
+86 137 5010 5351
EN
May. 21, 2026
After a CNC machined part is completed, it often needs to go through surface finishing before it can be put into use. Surface finishing not only affects the appearance of the part but also relates to important properties such as corrosion resistance, wear resistance, and cleanliness.
Among the many surface finishing methods, sandblasting, polishing, and brushing are the three most common. Each has its own characteristics and is suitable for different materials and applications. However, many people are not clear about the differences between these three methods. What is the difference between a sandblasted surface and a polished surface? What kind of parts is brushing suitable for? Which finishing method will give my product a better texture?
These are questions that almost every customer who needs CNC machined parts will ask. This article will compare sandblasting, polishing, and brushing in detail from multiple perspectives, including principles, effects, applicable scenarios, and costs, to help you make the most suitable choice for your CNC machined parts.
Before diving into the comparison of the three methods, let us first understand why CNC machined parts need surface finishing.
The surface of a part after CNC machining typically has tool marks left by cutting tools, minor burrs, or residual cutting fluid. If used directly, the appearance is not attractive enough, and the exposed metal surface is prone to oxidation and discoloration.
Surface finishing has three main purposes:
Remove machining marks and achieve a uniform, aesthetically pleasing surface texture. For consumer products, medical devices, high-end equipment, etc., appearance is a very important indicator.
Many metal materials gradually oxidize in air. Aluminum becomes dull and dark, and steel rusts. Appropriate surface finishing can form a protective layer on the metal surface to delay corrosion.
Certain surface finishing methods can change the physical properties of the surface, such as increasing hardness, reducing friction coefficient, or improving cleanliness.
Sandblasting, polishing, and brushing focus primarily on appearance improvement while also providing some degree of protection.
Sandblasting uses compressed air to propel fine abrasive particles at high speed onto the part surface. When the particles impact the metal surface, they create tiny craters, forming a uniform matte effect.
Different media produce different effects. Common media include glass beads, aluminum oxide sand, steel shots, and ceramic sand. Glass beads produce a relatively smooth surface with a matte silver appearance. Aluminum oxide sand produces a rougher surface with a uniform sandblasted texture. Steel shots produce a surface with some luster but less uniformity.
After sandblasting, the part surface has a uniform matte or sandblasted texture with no directionality, appearing consistent from all angles. This texture is understated and restrained, with no reflection, making it suitable for parts where a shiny surface is not desired.
Sandblasting can hide CNC machining marks and minor imperfections. If your part surface has slight tool marks, they will be basically invisible after sandblasting. This is a clear advantage of sandblasting over polishing and brushing.
Sandblasting is suitable for most metal materials, including aluminum alloys, stainless steel, titanium alloys, copper, and magnesium alloys. It is also suitable for plastics, but specialized plastic media must be used to avoid damaging the surface.
Typical applications include electronic device housings, medical device housings, automotive interior parts, tool handles, and decorative parts.
Sandblasted surfaces tend to attract dust and fingerprints and require frequent cleaning. The corrosion resistance of sandblasted surfaces is generally moderate. If higher corrosion protection is needed, anodizing or passivation is typically performed after sandblasting.
Sandblasting cannot produce high-gloss or mirror effects. If you need a part to reflect light like a mirror, sandblasting is not the right choice.
The equipment cost for sandblasting is moderate, and the operation is relatively simple. For small to medium batch parts, sandblasting is a low-cost surface finishing method. However, if the part has complex internal cavities and small holes, the residual abrasive needs to be carefully cleaned out after sandblasting, which adds some cost.
Polishing uses rotating polishing wheels or abrasive media to perform micro-cutting on the part surface, gradually removing microscopic protrusions to make the surface smooth and reflective.
Polishing is divided into mechanical polishing and electropolishing.
Mechanical polishing uses polishing wheels and polishing compounds to smooth the surface through physical friction. Mechanical polishing can achieve brightness levels ranging from matte to mirror, depending on the polishing wheel material and compound grit size.
Electropolishing involves immersing the part in an electrolyte solution and using an electric current to preferentially dissolve microscopic surface protrusions, resulting in a smooth surface. Electropolishing is only suitable for a few materials such as stainless steel and copper.
After polishing, the surface is very smooth and reflects light. Depending on the degree of polishing, it can achieve a semi-gloss, high-gloss, or mirror effect. A mirror-polished surface reflects images clearly like a mirror.
Polished surfaces do not easily attract dust and dirt and are very easy to clean. For parts that require frequent cleaning, such as food equipment and medical devices, polishing is a very suitable choice.
The disadvantage of polishing is that it amplifies imperfections. If the part surface has tool marks, scratches, or pores, they will become more noticeable after polishing. Therefore, polishing typically requires that the surface quality after machining is already very good.
Polishing is suitable for stainless steel, copper, aluminum alloys (which need protection after polishing), titanium alloys, etc.
Typical applications include medical devices (surgical instruments, implants), food processing equipment, architectural decorative parts, consumer electronic products, and mold cavities.
Polishing requires relatively high skill from operators, especially mirror polishing. Automated polishing equipment can reduce the dependence on manual labor, but the equipment investment is larger.
Mechanical polishing leaves microscopic polishing lines on the surface. Although they may be invisible to the naked eye, they still exist under a microscope. Electropolishing can achieve a more uniform, directionless surface, but the equipment investment is larger.
The labor cost for polishing is relatively high, especially for mirror polishing. For high-volume parts, using automated polishing equipment can reduce the per-part cost. Electropolishing has a larger equipment investment but lower labor cost, making it suitable for high-volume production.
Brushing uses abrasive belts or brushes to create uniform, continuous linear patterns on the part surface. These patterns can be straight or curved, depending on the brushing method.
Brushing typically uses abrasive belts of different grits, progressing from coarse to fine. Coarse belts produce deeper patterns, while fine belts produce more delicate textures.
After brushing, the surface has clear linear patterns with a distinctive industrial aesthetic. This texture has directionality, creating different reflective effects when viewed from different angles.
Brushing can hide minor scratches and imperfections because the new texture covers the original marks. However, if the imperfection is deep, brushing cannot completely eliminate it.
Brushed surfaces are more resistant to dirt than sandblasted surfaces because the consistent pattern direction does not easily trap dirt. However, the corrosion resistance of brushed surfaces is generally moderate, so anodizing or coating is typically applied after brushing for protection.
Brushing is suitable for aluminum alloys, stainless steel, copper, and other materials. Aluminum parts are typically anodized after brushing, while stainless steel parts can be used directly after brushing.
Typical applications include electronic product housings (laptops, mobile phones), home appliance panels, automotive interior parts, nameplates, and decorative trim.
Brushing can only be used on relatively flat surfaces. Complex curved surfaces, deep cavities, internal corners, and other areas are difficult to brush.
Brushing has directionality. If a part has multiple faces, the brushing direction needs to be carefully planned so that the textures on different faces are coordinated. If the directions are inconsistent, the appearance will look messy.
If a brushed surface is scratched, it is very difficult to repair because the texture of the repaired area cannot completely match the surrounding area.
Brushing can be done with automatic brushing machines or manually. For high-volume parts, automatic brushing has a lower cost. For low-volume or complex-shaped parts, manual brushing has a higher cost.
Sandblasting provides a uniform matte or sandblasted texture with no directionality, no reflection, understated and restrained.
Polishing provides a bright or mirror-like effect with strong reflection, showy and eye-catching.
Brushing provides a linear texture with directionality, an industrial aesthetic, somewhere between matte and glossy.
Sandblasting has the strongest imperfection hiding capability. Machining marks and minor scratches are basically invisible after sandblasting.
Brushing can hide minor scratches, but deeper imperfections remain visible.
Polishing amplifies imperfections and has the highest surface quality requirements from previous processes.
Polished surfaces are the smoothest, do not easily attract dirt, and are the easiest to clean.
Brushed surfaces have texture but with consistent direction, making cleaning moderately easy.
Sandblasted surfaces are the roughest, easily attract dust and fingerprints, and are more difficult to clean.
Sandblasting is suitable for most materials including aluminum, stainless steel, titanium, copper, and plastics.
Polishing is suitable for stainless steel, copper, aluminum (requires protection), titanium, etc.
Brushing is suitable for aluminum, stainless steel, copper, etc.
Sandblasting has the lowest cost, simple operation, and is suitable for small to medium batches.
Brushing has moderate cost, with automatic brushing having lower cost for high-volume production.
Polishing has the highest cost, especially mirror polishing, with high labor costs.
Recommend brushing or sandblasting.
Consumer electronic products such as laptops, mobile phones, and smart watches typically pursue understated and delicate appearances. Brushing can give the product a unique metallic texture, while sandblasting provides a uniform and fine matte effect. Both are very common. Polishing is too shiny and not suitable for such products.
Recommend polishing.
Medical devices such as surgical instruments and implants require extremely high cleanliness and biocompatibility. Polished surfaces are smooth, do not easily trap dirt, and are easy to disinfect and clean. Sandblasted surfaces are rough and can retain bacteria, making them unsuitable.
Recommend sandblasting.
Industrial equipment parts do not require showy appearances but need to hide machining marks and achieve a uniform look. Sandblasting has low cost and good effect, making it the most economical choice.
Recommend brushing or polishing.
Architectural decorative parts such as door and window handles, railings, and decorative panels need to be attractive and durable. Both brushing and polishing are common, depending on the design style. Brushing is understated, while polishing is showy.
Recommend polishing.
Food equipment needs to be cleaned frequently, and the surface must be smooth with no dead corners that can trap dirt. Polishing is the most suitable choice.
Recommend sandblasting.
In the prototype phase, appearance is not the most important factor, but machining marks need to be hidden to make the sample look professional. Sandblasting has low cost and good effect, making it the most suitable choice for prototypes.
In practice, sandblasting, polishing, and brushing are not mutually exclusive. Often, multiple surface finishing methods are combined on a single part.
Combination 1: Sandblasting + Polishing
First sandblast the entire part to achieve a uniform matte base, then polish specific areas to create a contrast between glossy and matte surfaces. This combination is common in high-end consumer products, such as the cases and bezels of high-end watches.
Combination 2: Brushing + Polishing
First brush to obtain linear texture, then polish edges or local areas to add a sense of layering. This combination is common in laptop housings, mobile phone frames, etc.
Combination 3: Sandblasting + Anodizing
For aluminum alloy parts, anodizing is typically performed after sandblasting. Sandblasting provides a uniform matte surface, and anodizing provides color and corrosion protection. This is the most classic surface finishing combination for aluminum alloy parts.
Q: Will sandblasted parts rust?
Sandblasting itself does not provide rust protection. For steel parts, the exposed surface after sandblasting is actually more prone to rust. Steel parts need to undergo rust protection treatment such as zinc plating, black oxide, or painting as soon as possible after sandblasting. Aluminum parts are recommended to be anodized after sandblasting.
Q: How long will a polished part maintain its brightness?
It depends on the usage environment. Stainless steel polished parts exposed to air will gradually oxidize and darken but will not rust. Aluminum parts polished without a protective layer will quickly oxidize and lose their luster. It is recommended to apply clear anodizing or clear coating to aluminum parts after polishing for protection.
Q: Can the direction of brushing patterns be customized?
Yes. The direction of brushing can be straight, diagonal, or curved, depending on the brushing equipment settings. However, brushing on complex curved surfaces is very difficult and is recommended only for relatively flat surfaces.
Q: Which surface finishing method is the cheapest?
Sandblasting is typically the cheapest due to simple equipment, fast operation, and low material cost. Brushing is the next cheapest. Polishing is the most expensive, especially mirror polishing.
Q: Do you offer these surface finishing methods?
Yes, Brightstar offers sandblasting, mechanical polishing, electropolishing, brushing, and many other surface finishing services. We can recommend the most suitable method based on your part material and application requirements.
Q: Does surface finishing affect part dimensions?
Yes. Sandblasting and brushing remove very little material, typically only a few microns, which is negligible for most parts. Mechanical polishing removes more material, especially when going from matte to mirror, which may remove 0.01 to 0.05 millimeters. If dimensional accuracy is critical, stock must be reserved during machining.
Sandblasting, polishing, and brushing are the three most commonly used surface finishing methods for CNC machined parts. Each has its own characteristics and is suitable for different scenarios.
Sandblasting provides a uniform matte sandblasted texture, has strong imperfection hiding capability, low cost, and is suitable for industrial equipment parts and prototypes.
Polishing provides a bright, mirror-like effect, has a smooth surface that is easy to clean, and is suitable for medical devices, food equipment, and high-end decorative parts.
Brushing provides a unique linear texture with industrial aesthetics and is suitable for consumer electronic product housings and architectural decorative parts.
Choosing the right surface finishing method depends on your part material, usage environment, appearance requirements, and budget constraints. If unsure, you can consult with a professional machinist who can provide recommendations based on experience.
Brightstar provides one-stop services from CNC machining to surface finishing. Whether you need sandblasting, polishing, or brushing, we can complete it for you, ensuring that both the appearance and performance of your parts meet your requirements.
Ready to Choose a Surface Finish for Your CNC Machined Parts?
Whether you need understated sandblasting, showy polishing, or brushing with industrial aesthetics, Brightstar can provide professional surface finishing services.
Email Amy: amy@brightstarprototype.com
Call or WhatsApp: +86 13750105351
Send us your CAD files and drawings for a free surface finishing recommendation and quote.
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