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Finishing Treatment

Surface finishing can improve the appearance and properties like corrosion resistance, tarnish resistance, chemical resistance, wear
resistance, and hardness, modifying electrical conductivity, removing burrs or applying specific colors to the machined components. It usually through adding a layer of metal or non-metal coating on the exterior of a metallic workpiece.

We can provide several different surface finishing options for CNC machining, including aluminum anodizing, plating, sandblasting, Passivation, Polishing, Powder Coating, Black Oxide coating, heat Treatment, etc. 

Hi quality surface finishing treatment

We will introduce our most common used metal finishes at the following page, if your required surface finishing not included here, just contact us for more detail.

red black clear color anodizing

Anodizing is one of the most common finishing options, using electrochemistry to create a layer of aluminum oxide film on the surface of aluminum or aluminum alloy, to improve corrosion resistance, wear resistance and hardness, and protect the parts surface. Additional, anodizing makes the parts very easy to color and get very smooth surface, thus, anodized parts are very popular in the consumer electronics industry, where the smooth and beautiful appearance is very important.

Available anodizing color: Clear, black, blue, gold, grey, red, etc.
Applied raw material: Aluminum, magnesium, copper, titanium, zinc, etc. Most commonly used at aluminum material.

Design Considerations
• Anodizing coating layer is non-conductive, so anodized parts have weak electrical conductivity.
• All edges and corners on the workpiece should be rounded with a radius of no less than 0.5 mm, and no burrs are allowed.
• For very high precision CNC machining parts, be cautions to use anodizing, because the anodizing layer can slightly change parts dimensions

Chromium plating, Nickel plating, Zinc plating

Plating is a process where a conductive surface is covered with a very thin metal coating layer. Plating is commonly used to prevent corrosion, increase durability, alter surface friction, and improve appearance.

Plating type: Chromium plating, Nickel plating, Zinc plating.

Material: Aluminum, Brass, Stainless Steel, Steel, etc

Design Considerations
• Plating thickness should be taken into consideration at where dimensions tolerance is critical
• Due to the very thin plating coating layer, plating does not get the parts surface smoothly obviously.
• Plating materials should be chosen based on the desired characteristics of the final part: corrosion resistance, strength, etc.

Abrasive Blasting, Bead Blasting, Sandblasting

Bead blasting also named abrasive blasting or sand blasting, is the process shooting small abrasive material composed of high-velocity sand-sizes particles against the metal surface under high pressure with blast equipment to remove surface contaminants, clean metals or increase a texture, then change the smoothness or roughness of surface.

Bead blasting is primarily used for aesthetic applications that require good visual qualities.

Material: Most metal and plastic, like ABS, Aluminum, Brass, Stainless Steel, Steel.

stainless steel passivation finishing process

Passivation is a widely-used metal finishing process to prevent corrosion.

Passivation main process:
• Cleaning: Grease, coolant or other shop debris must be thoroughly cleaned from the surface to obtain the best possible corrosion resistance.
• Passivating acid bath: After cleaning, the part is ready for immersion in a passivating acid bath. Any one of three approaches can be used—nitric acid passivation, nitric acid with sodium dichromate passivation and citric acid passivation. Which approach to use depends on material and specification requirement.

Material available for passivation:
Stainless steel, Aluminium, Ferrous materials, Titanium, Nickel, Silicon.
Most common material we use for passivation finishing is stainless steel. Stainless steels are corrosion-resistant, but they are not completely impervious to rusting.
For stainless steel, the passivation process uses nitric acid or citric acid to remove free iron from the surface. The chemical treatment leads to a protective oxide layer that is less likely to chemically react with air and cause corrosion.

polishing surface finishing

Buff polishing creates a smooth near-mirror uniform surface by physical rubbing or chemical interference. Polishing can improve the appearance of new or used metal parts.

Material: Aluminum, Brass, Stainless Steel, Steel, etc
Polishing type: Mechanical polishing, chemical polishing

Design Considerations
• Plastic material is not suitable for polishing treatment.
• Polishing surface finishing is not suitable for the CNC machined components with very complicated structures
• Very tight tolearance components is not suitable for polishing.
• Harder metal can get better polishing efficience, but cost much more.
• It is possible polishing may not be effective on parts that contain sharp, intricate, recessed, or fragile features.

CNC machining powder coating surface finishing

Powder coating is a finishing process that applying a thin dry powdered plastic layer to the machined part to improve strength, wear-resistance and durability.

Powder coating is compatible with all machining metals, and this process also allows wide range of color options, which bring great flexibility to designers

Color: Blue, Orange, Red, Purple, Pink, Green, Brown, Tan, Yellow, etc

Design Considerations
• Powder coating adds 0.001″ – 0.003″ to each surface and slightly rounds edges will exist, and this might affect the dimensional tolerances of the finished machined parts.
• Deep pockets and inside corners may not be coated due to the electrostatic process.

Black Oxide cnc machining parts surface finishing

Black oxide is a low-cost finishing treatment. Black oxide is the process that submerging ferrous parts into a hot alkaline aqueous salt solution bath, a chemical reaction happend and create a black magnetite coating. The black oxide coating can improve corrosion resistance, minimize light reflection and improve appearance of the CNC machined parts

cnc machining heat treatment

Heat Treatment is the process through utilizing heating or chilling usually under extreme temperatures to make the metal achieve a certain state or change some characteristics

Heat treatment type: Annealing, tempering, hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching.

Hi Quality Precision Machining support 20+ surface finishing for CNC machined parts, not limited of above mentioned type. Please contact us for more details.

Online service

Skype: suel1981@gmail.com Alan@hqmachining.com