Common Surface Treatments for CNC Machined Parts

Surface treatments form a layer of one or more special properties on the surface of the material by physical or chemical means. Surface treatment can improve the appearance, texture, function, and other aspects of the product.

In the machining industry, anodizing, rust, or other conditions may appear on the surface during processing, transportation, storage, use, etc. Therefore, we often do another layer of surface treatment on the surface of the CNC parts to ensure good performance and corrosion resistance of the product and prolong its service life. Of course, some surface treatments may also be decorative – helping provide easy identification of parts, or camouflage for more discreet application, or even just to make them more aesthetically pleasing.


Different materials and products will use different surface treatments. At Weimi, we often use the following surface processing methods for our client’s products:

Anodizing: There are many anodizing methods for aluminium alloy – this process produces a hard, protective layer on the surface of aluminium parts, that can add colour to the parts and be used for decoration or achieve a functional benefit. Anodizing requires high-quality products as different materials have different surface textures and this can create different decorative effects on the surface of the parts. The most commonly-used aluminium materials are 6061, 7075, 6063. We’ve recently used this process in the manufacture of switch panels, aluminium electronic cigarette cases, and communication equipment parts that we make for customers in the electronics industry. There is no limit to the colours we can create using this method – making it one of the most versatile surface treatments we offer.

Black coating: a black coating is a common means of chemical surface treatment that produces a layer of anodizing film on the metal surface to isolate air and achieve greater rust prevention. If our client does not specify their requirements for the outer appearance of the parts, we generally recommend black coating as standard as it’s the most efficient for use on iron parts.

Brushing: surface brushing is a kind of surface treatment that creates line patterns on the surface of the CNC parts and is achieved by grinding the product to give a decorative effect. As the surface brushing treatment can provide a very uniform matte texture on metal materials, it has become more and more popular and widely is used by our customers. Compared to other surface treatments, brushing can make the metal surface obtain non-specular metallic lustre, which has a wonderful decorative effect like silk satin.


In the construction industry, there are elevator door plates and escalator decorative plates that use this treatment, and in the construction hardware industry, we use this treatment on hinges, handles, locks and more for a modern look that is very popular in some markets.


We recently customized various 3C digital products for customers, such as laptop panels, keyboard panels, mobile phone panels, LCD frames, battery cover plates, camera protection slide covers, digital camera lens slide cover plates, and lots more. There are other kinds of electronic products, such as music players, projectors, and others that are made from aluminium alloy and stainless steel – making them very suitable for this type of brushing, and very popular in the industry.

Polishing: the function of polishing is to remove the oxide and corrosion from the product’s surface and restore the cleanness of the paint surface. It can also reduce the surface roughness of the CNC parts and obtain a bright, flat surface that is more appealing to the touch. Generally, if the customer uses stainless steel materials, they will also request a polishing treatment at the end – this is mostly performed on stainless steel components to improve their appearance. After mechanical polishing and electropolishing, aluminium parts can develop a mirror-like effect that is increasingly becoming more popular around the world.

Sandblasting: this kind of surface treatment is commonly used for aluminium to overcome defects in the machining process of aluminium alloy – recently, we used this method for a client’s order to help meet their requirements for the product’s aesthetic appearance. We can use glass sand, carborundum, tungsten sand, and others to give different effects on the machined parts, including matte or shiny finishes. Generally, we will use this kind of surface treatment on aluminium products to help customers achieve a beautiful matte effect on the product surface.

Electroplating: electroplating is the process of plating a layer of other metals or alloys on the metal surface, to prevent metal anodizing (e.g. rusting), improve wear resistance and conductivity, make the metal more resistant to corrosion, and enhance aesthetics. (Fun fact: the outer layer of many coins is also electroplated!)



In addition to metal, plastic products can also be electroplated, however, the process involves additional steps. These processes may vary, as will the needs and functions of electroplating:


  • Copper plating is used for backing to improve the adhesion and corrosion resistance of the plating layer. (Copper is easy to anodize, after which it turns green and loses conductivity. Therefore copper-plated products must undergo a protection procedure for the copper surface).


  • Nickel plating is used for backing or appearance, to improve corrosion resistance and wear resistance.


  • Gold plating to improve conductive contact resistance, improve signal transmission (gold is the most stable and most expensive).


  • Zinc plating is a surface treatment technology that plates a layer of zinc on the surface of the materials for aesthetic reasons or to prevent rust. Generally, the main method is hot galvanizing.


  • Silver plating improves conductive contact impedance and enhances signal transmission.


  • Spraying powder coating refers to using a layer of fine dust and can help achieve specific colour properties, or for protection. This process is often used in our customized sheet metal parts but can also be used when coating plastics to form a solid continuous coating layer on the surface.


Weimi can provide a range of CNC services and we would welcome the opportunity to discuss your project needs and requirements. Contact us to find out more.

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