Home 9 Design Guide 9 A Practical Guide to Surface Treatments in Machining

A Practical Guide to Surface Treatments in Machining

Author: Yaozu Deng
Published on: 2023-03-22

Performing powder coating finish with a spray gun for steel parts

Surface treatment process

The surface quality of machined parts is essential in manufacturing regarding their functionality, durability, and aesthetic appeal. Most parts or products need surface treatment procedures to achieve the desired finish because the machined surface often contains tool marks, burrs, chips, or other flaws.

A suitable surface treatment technique can address all surface defects, providing a longer lifespan for the parts. So, it is an essential aspect of manufacturing in several industries, including automotive, aerospace, and medical, where precision and dependability are essential.

This article will explore the importance of surface treatments, various finishing techniques, and procedures to choose the suitable surface finish for your machined parts.


What Is a Surface Finish?

Surface finish refers to a surface’s texture, roughness, and overall quality after manufacturing. Moreover, it can be defined as a surface’s condition after being subjected to different surface treatment processes, such as polishing, grinding, sandblasting, or coating.

The surface finish can be expressed with different mathematical parameters, including roughness, waviness, and flatness. These parameters are often measured with various metrological instruments and measurement principles.

The following are some commonly used techniques in surface finish measurements.

These techniques measure the height and spacing of surface features (such as waviness and flatness).


The Value of Surface Finish: Why it should Not Be Overlooked

The quality of the surface finish can significantly impact a product’s performance. For instance, a rough surface cause friction, wear, and tear on moving parts, whereas a smooth surface can increase the product’s durability and prevent wear.

Now, let’s discuss some key points regarding why surface finish cannot be overlooked in the manufacturing industry.

  1. It affects the functionality of the final product.

The surface quality of machining parts affects the measurement accuracy, friction, wear, tear, and other factors related to the functionality of individual parts or products. For example, a poor finish surface degrades over time, causing high friction and low functionality.

  1. Product durability

The surface finish of a product can also affect its durability. Because of microscopic fissures and pores that can collect moisture, dirt, or other impurities, a product with a rough surface is more prone to corrosion, cracking, or degradation over time. However, a smooth surface is more corrosion-resistant and less likely to trap pollutants, extending the product’s lifespan.

  1. Appearance and brand image

The surface finish of a product influences its appearance, which is especially essential in industries like automotive, aerospace, and consumer goods.

A product with a high-quality surface finish appears more professional, which can promote brand image and customer perception. Furthermore, a high-quality surface finish can drive sales by making a product more attractive to customers.

  1. Compliance with industry standards

Many industries have surface finish or surface roughness standards to ensure that parts or products meet specific performance and durability criteria. For example, the aerospace industry has stringent surface finish criteria to ensure the safety and reliability of aircraft components.

Therefore, a high-quality surface finish is fundamental to several specific criteria across different industries.

  1. Cost-effectiveness of a product

High-quality surface finishes are less likely to require repairs or replacements due to wear or corrosion, lowering maintenance costs and improving product longevity. Furthermore, a high-quality surface finish can eliminate the need for additional coatings or finishes, lowering manufacturing costs.


Classification of Surface Treatment Approaches

There are several surface treatment approaches for machining parts or products, each with its own set of benefits and drawbacks. However, mechanical, Chemical, heat treatment, and coating surface treatments are the most popular in manufacturing. Let’s discuss each of them in detail.

Mechanical surface treatments

The mechanical surface treatment process involves using mechanical force to modify the surface of machined parts. It can be carried out in various ways, such as grinding, polishing, shot peening, sandblasting, and brushing.

The mechanical surface treatment is ideal for removing surface flaws, creating a smooth surface, and improving the material’s wear and tear resilience. The method can generate a specific surface texture or finish to improve the aesthetic attractiveness of the material.

Chemical surface treatments

As the name suggested, chemical surface treatment involves using suitable Chemical solutions to modify the surface of machined parts. The chemical solution reacts with the parts and creates a protective layer that improves resistance to corrosion, oxidation, and wear.

The standard techniques for achieving Chemical surface treatments include etching, anodizing, electroplating, and passivation.

Coating surface treatments

The coating treatment process entails the development of a thin protective layer on the material surface to enhance its corrosion and abrasion resistance. It can be carried out with different techniques, such as powder coating, electroplating, Alodine Coating, Chemical vapor deposition, and painting.

Heat treatments

The heat treatment process involves using heat to alter a material’s properties by customizing microstructures in the material. It can be achieved through techniques such as annealing, quenching, tempering, and case hardening.

A heat treatment finish is suitable for improving the material’s mechanical properties, such as its strength, toughness, and ductility, to improve its performance in specific applications.


Let’s Start A New Project Today

What Are the Different Types of Surface Finishes Available?

In CNC machining or other manufacturing, surface finishes play a significant role in creating a high-quality final product. Various techniques are available to achieve the desired surface quality, including plating, powder coating, galvanization, anodizing, and laser cladding. Let’s discuss each of these finishing options in more depth.

Plating finish

Steel parts after electroless-nickel plating

Nickel plated parts

The process of depositing a thin layer of metal onto a substrate to create an attractive and corrosion-resistant surface is known as a plating finish. The plating metal can be anything from gold to nickel and zinc.

The plating of metal is not only used in decorative items and jewelry, but it also provides a protective cover for electronics, automotive, and aerospace components.

Powder coating

Powder coating finish parts with various colors

Powder coated parts

Powder coating is a popular coating approach in manufacturing that involves the application of a dry and finely ground powder onto a metal surface through an electrostatic deposition. Firstly, the machined parts are dipped into dye powder. Then, the parts are baked in an oven where it melts and forms a durable and protective layer. As a result, a smooth and even finish is created that is resistant to chipping, cracking, and fading.

Powder coating finish can be employed on metallic and non-metallic parts. However, it is a preferred choice for metal surface finishing.

Galvanization finish

Galvanization finish refers to the process of coating metal parts with a zinc layer to prevent rusting and corroding. It is used in various industries such as construction, automotive, and marine, where metals are exposed to harsh environments and require protection to maintain their structural integrity.

Drying steel structural parts after galvanization

Galvanized parts

The galvanization process involves two major steps; cleaning the metal surface and coating with different techniques (hot-dip, electro-, and spray galvanization). In addition, the coating thickness depends on the application and can range from a few microns to several millimeters.

Anodizing finish

Aluminum part with anodizing surface finish

Anodized parts

Anodizing is another surface finishing process used to optimize the durability and appearance of machined parts or products, particularly those used in industrial and aerospace applications.

The process involves the creation of a protective oxide layer on the metal surface using electrochemical deposition. The anodizing finish particularly applies to aluminum. However, it can be used for other metals such as titanium, zinc, and magnesium.

Anodizing is the best alternative to powder coating for surface finishing of machining parts with intricate shapes. It offers exceptional color retentions for finished parts over a long time.

Laser cladding finish

Laser cladding refers to creating a coating layer on the material surface by melting and fusing metallic powders using a laser beam. The coating formed by laser cladding methods improves the substrate material’s abrasion resistance, corrosion resistance, strength, and surface hardness.

A schematic diagram describing the working of laser cladding finish

Laser cladding finish

In the laser cladding process, the surface finish quality is affected by several factors, such as laser power, powder feed rate, beam size, scanning speed, and layer thickness. For example, higher laser power and slower scanning speed result in a smoother surface finish.


How to Choose the Perfect Surface Finish for Your Machining Parts?

Choosing the suitable surface finish for your machining parts is essential for achieving the desired functionality and appearance of the component. However, there is no such perfect surface finish technique for your machining project because it entirely depends on the specification of a particular part or product.

Let’s discuss the step-by-step procedure for selecting surface finishing techniques for any machined parts or products.

Step 1: Determine the function of the part

The first step in choosing the surface finish is to determine the function of the part. Different applications require different surface finishes to achieve the desired performance. For example, parts used in high-wear environments (like bearings and gears) require a smooth surface finish to reduce friction. On the other hand, parts used in corrosive environments, such as marine and chemical industries, require a highly corrosion-resistant surface finish.

Consideration: The function of the part determines the surface finish requirements, and choosing the wrong surface finish can result in premature failure of the product or low performance.

Step 2: Identify the part’s material

The second step is to identify the part’s material since the requirement of surface finishing also depends on their properties, such as hardness, ductility, and thermal conductivity. For example, softer materials such as aluminum require a smoother surface finish than harder materials such as steel.

Consideration: The part’s material determines the surface finish requirements, and choosing the wrong surface finish can damage the part or cause poor performance.

Step 3: Determine the machining process

Determine which machining process is used in manufacturing parts, such as conventional milling, CNC machining, EDM, or others. The as-machined surface finish depends on the machining process used to create the parts. Furthermore, it helps to analyze which surface finishing approach is suitable for achieving the desired finish.

Consideration: The manufacturing process determines the surface finish requirements, and choosing the wrong surface finish can result in poor quality or inconsistent performance.

Step 4: Specify the Surface Finish Requirements

The surface finish is typically specified in terms of roughness, which is the surface deviation from a perfect plane. The roughness is measured in units of micrometers (µm) or microinches (µin). The surface finish requirements are usually specified in engineering drawings or specifications.

Consideration: The surface finish requirements should be realistic and achievable with the chosen manufacturing process, material, and intended application.

Step 5: Choose the surface finish method

The final step is to choose the surface finish method. There are several methods to achieve the desired surface finish, including grinding, polishing, sandblasting, and chemical treatments. The choice of method depends on the surface finish requirements, the part’s material, and the manufacturing process used.

Consideration: The surface finish method must be repeatable, cost-effective, and consistent according to the part’s specifications.



The surface treatments are essential for any machining parts in terms of their functionality, performance, durability, and aesthetic appearance. However, choosing the suitable surface finish for your machining parts requires thoroughly understanding the part’s function material, machining method, and finish requirements.

At ProleanTech, we provide various surface finishing services based on your needs and consultation from expert engineers. Therefore, contact us, and we will provide a suitable finish for optimal performance and aesthetic of your parts.


Why is surface finish essential in manufacturing?

The quality of the surface finish can significantly impact a product’s performance, measurement accuracy, friction, wear, and tear. A high-quality surface finish can increase a product’s durability, prevent wear, improve appearance, promote brand image, and drive sales.

What are the different types of surface treatment approaches?

The types of surface treatment approaches for machining parts or products are mechanical, chemical, heat treatment, and coating surface treatments.

What are the different types of surface finishing?

Various techniques are available to achieve the desired surface quality, including plating, powder coating, galvanization, anodizing, and laser cladding.


Submit a Comment

Your email address will not be published. Required fields are marked *

You may also like


Get Your Parts Made Today


  All uploads are secure and confidential.