Complete Guide to Surface Treatments for CNC Milled Parts
Surface treatments play a vital role in enhancing the performance, durability, and appearance of CNC milled parts. Whether you are producing components for aerospace, automotive, medical devices, or industrial machinery, the right surface treatment can improve corrosion resistance, reduce wear, and even add a visually appealing finish.
In this guide, we explore the most common types of surface treatments, explain how to choose the right one for your application, and highlight meviy’s capabilities for applying high-quality surface finishes to steel and aluminium CNC milled parts.
What Are Surface Treatments?
Surface treatments refer to processes applied to the exterior of a part to enhance its properties. Unlike coatings, which are often applied over a protective layer, surface treatments can alter the material itself or add a functional layer.
The main purposes include:
- Improving corrosion resistance
- Increasing wear and fatigue resistance
- Enhancing surface aesthetics
- Reducing friction or improving adhesion for paints and coatings
Choosing the right surface treatment is crucial, as it directly affects the lifespan and performance of your CNC milled parts.
Common Types of Surface Treatments for CNC Milled Parts
Mechanical Surface Treatments
Mechanical treatments involve physically altering the surface of a part. Examples include:
- Polishing: Produces a smooth, reflective finish.
- Brushing: Creates a uniform directional texture.
- Shot peening: Introduces compressive stresses to increase fatigue resistance.
- Sandblasting: Cleans the surface and provides a matte finish.
These treatments improve surface finish, reduce micro-cracks, and can enhance the mechanical performance of the component.
Chemical Surface Treatments
Chemical processes modify the surface at a microscopic level. Common methods include:
- Anodising: Creates a protective oxide layer on aluminium.
- Phosphating: Provides corrosion protection and improves paint adhesion.
- Chemical passivation: Enhances the natural corrosion resistance of stainless steel.
Chemical treatments are often chosen for their ability to provide uniform protection and prepare surfaces for additional coatings.
Electrochemical Surface Treatments
Electrochemical methods use electrical or chemical processes to deposit or alter a surface. Typical examples are:
- Electroplating: Deposits a thin metal layer for corrosion resistance or decoration.
- Electroless nickel plating: Provides uniform coating without electricity, ideal for complex geometries.
- Hard chrome plating: Adds wear resistance and reduces friction.
These treatments are particularly useful when surface hardness, corrosion protection, and visual appeal are critical.
Thermal Surface Treatments
Thermal processes modify the surface through heat treatment. Examples include:
- Nitriding: Increases surface hardness without affecting core properties.
- Carburising: Enriches the surface with carbon for wear resistance.
- Induction hardening: Hardens specific areas while preserving the part’s overall toughness.
Thermal treatments are ideal for components subjected to high stress or friction.
Coatings and Paints
- Powder coating: Provides a durable, protective finish.
- Liquid paints: Offer corrosion protection and aesthetic appeal.
- PTFE coatings: Reduce friction and improve chemical resistance.
Coatings are often applied after surface treatment to combine functional and decorative benefits.
meviy’s Main Surface Treatments for CNC Milled Parts
meviy offers a range of surface treatment options specifically designed for steel and aluminium CNC milled parts, allowing engineers to select treatments during the quotation process. This ensures compatibility with part geometry, material, and functional requirements.
Steel:
- Black Oxide
- Electroless Nickel
- Trivalent Chromate (Clear)
- Trivalent Chromate (Black)
- Hard Chrome Plating (Flash Plating)
- Nitriding
- Phosphating (Manganese)
- LTBC – Surface Treatment
| Surface Treatment | Technical Features | Benefits | Typical Applications |
|---|---|---|---|
| Black Oxide | Chemical conversion coating | Corrosion resistance, reduced glare, minimal dimensional change | Fasteners, gears, tool components |
| Electroless Nickel | Uniform nickel layer without electricity | Corrosion resistance, wear protection, uniform coverage on complex geometries | Valves, aerospace parts, mould components |
| Trivalent Chromate (Clear) | Passivation layer | Corrosion resistance, environmentally friendly | Automotive, machinery, general metal parts |
| Trivalent Chromate (Black) | Black passivation layer | Corrosion resistance, aesthetic finish | Screws, brackets, visible components |
| Hard Chrome Plating (Flash Plating) | Thin hard chromium layer | High wear resistance, low friction | Hydraulic parts, shafts, industrial machinery |
| Nitriding | Thermochemical diffusion of nitrogen | Increased surface hardness, fatigue resistance | Engine parts, gears, bearings |
| Phosphating (Manganese) | Chemical phosphate coating | Corrosion protection, improves paint adhesion | Automotive components, coated metal parts |
| LTBC – Surface Treatment | Proprietary treatment | Enhanced corrosion resistance and surface durability | Custom applications requiring high performance |
Aluminium:
- Clear Anodise
- Clear Anodise (Matt)
- Black Anodise
- Black Anodise (Matt)
- Hard Anodise (Clear)
- Hard Anodise (Clear, Matt)
- Gold Anodise
- Red Anodise
- Electroless Nickel
| Surface Treatment | Technical Features | Benefits | Typical Applications |
|---|---|---|---|
| Clear Anodise | Thin, transparent oxide layer | Corrosion resistance, aesthetic glossy finish | Enclosures, housings, consumer electronics |
| Clear Anodise (Matt) | Thin matte oxide layer | Corrosion protection with non-reflective surface | Decorative components, visible housings |
| Black Anodise | Thin black oxide layer | Corrosion resistance, enhanced aesthetics | Consumer electronics, automotive trim |
| Black Anodise (Matt) | Matte black oxide layer | Corrosion protection, reduced glare | Architectural components, visible parts |
| Hard Anodise (Clear) | Thick, hard oxide layer | High wear resistance, corrosion protection | Industrial parts, aerospace components |
| Hard Anodise (Clear, Matt) | Thick matte oxide layer | Wear and corrosion resistance with matte finish | Heavy-duty parts, mechanical assemblies |
| Gold Anodise | Decorative anodised layer | Corrosion resistance, premium aesthetic | Consumer products, decorative parts |
| Red Anodise | Decorative anodised layer | Corrosion resistance, vibrant aesthetic | Consumer products, visible housings |
| Electroless Nickel | Uniform nickel coating | Corrosion protection, wear resistance, uniform coverage | Aerospace, machinery, precision components |
meviy streamlines the process, allowing engineers to receive instant quotations with the desired surface treatment applied, ensuring faster and more efficient procurement of high-quality CNC milled parts.
How to Choose the Right Surface Treatment
Selecting the optimal surface treatment depends on several factors:
- Material compatibility: Steel and aluminium have different treatment options.
- Functional requirements: Consider corrosion resistance, wear resistance, friction reduction, and aesthetics.
- Cost and production scale: Some treatments are more economical for high-volume production.
- Environmental and regulatory compliance: Ensure treatments meet relevant standards and environmental regulations.
By carefully evaluating these factors, engineers can select a treatment that balances performance, longevity, and cost.
Industry Applications
Surface treatments are widely used across industries:
- Automotive: Hard chrome plating for engine components, anodising for aluminium parts.
- Aerospace: Electroless nickel plating and hard anodising for lightweight, durable parts.
- Medical devices: Electroless nickel and anodising for corrosion-resistant, biocompatible surfaces.
- Electronics: Phosphating and coatings to protect against oxidation and wear.
Surface Treatment Standards and Quality Control
Ensuring quality and consistency requires adherence to standards such as ISO, ASTM, or JIS. Key inspection methods include:
- Visual inspection
- Thickness measurement
- Hardness testing
Implementing robust quality control helps prevent defects, ensures compliance, and maintains the performance of CNC milled parts.
FAQs
Q: Can aluminium CNC milled parts be electroless nickel plated?
Yes, meviy supports electroless nickel plating for aluminium parts, providing uniform corrosion protection and wear resistance.
Q: What is the difference between anodising and powder coating?
Anodising chemically modifies the aluminium surface to form a protective oxide layer, whereas powder coating applies a separate protective and decorative layer.
Q: Are all surface treatments suitable for all CNC milled materials?
No, treatments must be chosen based on material compatibility. For example, nitriding is only suitable for steel, not aluminium.
Q: How does meviy simplify surface treatments for CNC parts?
meviy allows engineers to upload 3D CAD models, select the desired surface treatment, and receive instant quotations with manufacturability checks, reducing procurement time and ensuring precision.
What is meviy
meviy is an AI-powered on-demand manufacturing platform from MISUMI. Engineers can upload 3D CAD models to receive instant quotations, manufacturability checks, and lead time estimates. The platform delivers bespoke components to exact specifications across CNC milling, CNC Turning and Sheet Metals. With no minimum order quantity, teams can order from a single part upwards. By streamlining procurement and accelerating product development, meviy enables engineers to bring designs to life faster. Its AI also supports part recognition, interactive design editing, and compatibility with a wide range of materials – making it a smart and reliable tool for modern product development. Backed by MISUMI’s quality standards, customers can expect consistent precision with every order.
