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Electropolishing is a method of smoothing metal that is similar to polishing. However, in practice, it is more advanced. Most often, electropolishing is used for stainless steel and other similar metals. The process makes the surface shiny, smooth, and aesthetically pleasing. Many people confuse electropolishing with passivation, but they are different processes. In practice, each helps the metal to better cope with corrosion, but as a rule - only electropolishing uses electric current. In addition, electropolishing makes the surface of the metal less rough, even by half. Electropolishing is a great process that works well for delicate metal items or complicated shapes. It works similarly to reverse electroplating. Electropolishing uses an electric current instead of applying a thin layer of metal. Even though there is a lot of debate in the world of metallurgy about the effectiveness of electropolishing in combating corrosion, it is undoubtedly a process worth knowing and using if you want an exceptionally smooth and clean metal surface.

Aluminum and electropolishing

Aluminum is now being used more frequently in the CNC industry. This product is cheap, easy to work with, and lightweight. But the problem is its finish. Electropolishing helps solve this problem. Electropolishing is a way of improving the appearance of the aluminum surface to make it smooth and clean. This is important when aluminum is to be used in clean areas, such as in laser equipment.

In aluminum, there are two main types: 

  • cast alloys
  • a product for forming. 

Cast alloys can be melted quickly, but they have an inferior finish. Wrought alloys are different - electropolished aluminum of this type has a smooth surface without impurities. For aluminum - electropolishing involves passing an electric current through aluminum in a unique solution. The current dissolves bumps on the aluminum surface, making it smooth.

It is essential to use the right chemicals when electropolishing. Traditionally, perchloric acid is used, but it has safety and environmental problems. An alternative that is less hazardous to humans and the environment is the so-called deep eutectic solvents (DES). It's also worth pointing out that electropolishing aluminum has many advantages, such as more excellent corrosion resistance, better surface finish, ease of cleaning, nice appearance, and longer part life. 

Advantages of electropolishing aluminum

Why is aluminum electropolishing used? This is because corrosion most often starts on the surface of this metal. Unfortunately, various manufacturing processes can deteriorate the condition and properties of the aluminum surface. For example, it can be pointed out that during welding, machining, or other manufacturing processes, various impurities such as metal particles, iron, dirt, or grease can be deposited on the surface of aluminum. Mechanical polishing, cutting, or other processing can lead to foreign iron particles or other abrasive substances deposition. These impurities can destroy the natural aluminum oxide layer that protects against corrosion. If it is damaged, the corrosion process begins. The solution to the problem is electropolishing. This process involves dissolving a thin layer of aluminum surface along with impurities. This removes embedded particles, which in turn increases the life of the component. But let's not forget that electropolishing of aluminum also has other benefits. After such treatment, the surface becomes more resistant to corrosion, looks better, is less sticky, and is easier to clean. In addition, electropolishing helps remove bumps, giving aluminum an attractive appearance. An added bonus is that electropolished aluminum is more resistant to various types of corrosion, such as pitting, galvanic, surface, crevice, cracking, stress corrosion, and microbiological corrosion.


What is chemical-mechanical polishing?

Chemical-mechanical polishing, also known as CMP, is a process in which the top surface of a tile is polished using a slurry. The slurry contains unique grains, which, combined with the appropriate chemistry, lead to the abrasion of the product layer. This means, in practice, that the process consists of a chemical part and a mechanical part. 

  • The mechanical aspect involves downward pressure.
  • The chemical action helps speed up the removal of the material. 
  • The speed of the process depends on the type of material being treated.
  • Application of electropolishing in practice

Electropolishing is a method that has been used since the 1950s. As we mentioned earlier, the process itself works in two ways: mechanically and chemically. The most common use of such products is in industries such as: 

  • Medical: Surgeons and dentists use electropolishing to keep instruments clean and in working order.
  • Food and pharmaceutical industry: It benefits from the sterilizing properties of electropolishing.
  • Domestic appliance manufacturing: Electropolishing improves the durability and aesthetics of components in appliances such as refrigerators and washing machines.
  • Aerospace industry: This sector uses electropolishing on critical parts to minimize friction and maximize performance.
  • Semiconductor manufacturing: Uses electropolishing for precision machining of delicate products with irregular shapes.
  • Automotive: Automobile manufacturers and the racing sector use electropolishing on parts such as transmissions and fuel lines to help reduce friction, improve performance, and extend part life.


Electropolishing is often used to treat parts such as:


  • Pipes and tubes
  • Fasteners
  • Springs
  • Wire racks
  • Blades

What is the electropolishing of stainless steel?

Like aluminum, electropolishing makes stainless steel smooth, shiny, and free of impurities, further increasing its corrosion resistance. Although the process can be applied to various metals, 300- and 400-series stainless steel alloys are most commonly used. 400 series stainless steel offers better hardness and strength but is more susceptible to corrosion - electropolishing allows these characteristics to be maintained while increasing corrosion resistance. Other examples of metals subject to electropolishing include the previously mentioned aluminum, brass, carbon steels, cobalt chrome, copper alloys, nickel alloys, titanium, and nitinol. However, it is worth remembering that electropolishing is not always practical for cast metals, such as those that contain a lot of silicon, sulfur, or carbon.

Electropolishing copper 

Electropolishing copper is a process that begins by cleaning the surface of the metal using a suitable chemical solution. The copper is then immersed in an electrolytic bath with sulfuric or hydrochloric acid, and the application of a voltage leads to the attraction of ions from the solution to the copper surface, removing impurities. What are the benefits of this process? Electropolishing protects the surface from corrosion and oxidation. In addition, the surface becomes smooth, making it easier to clean and preventing dirt or bacteria deposition. Another aspect is that the process prolongs the life of metal parts. Consequently, electropolishing can improve the efficiency of manufacturing processes through better dimensional tolerances and reduced friction. 

What are the advantages of electropolishing? 

Electropolishing is a process that can be successfully used in CNC companies. It is a surface treatment method that uses electrochemical phenomena to improve the quality and appearance of metal parts. The advantages of this method are as follows:

  • Improved aesthetics: Electropolishing can significantly improve the appearance of metal parts. The process removes bumps, scratches, and other surface defects, giving metal parts a smooth and shiny surface.
  • Removing oxides and contaminants: The electropolishing process removes oxides, rust, deposits, and other contaminants from the surface of metal parts. This process ensures cleanliness and improves the durability of the parts.
  • Improving corrosion resistance: Electropolishing creates a layer of oxides on the metal surface, protecting components from corrosion. This additional protective layer benefits components exposed to weathering and aggressive environments.
  • Fluid flow optimization: the electropolishing treatment can improve the quality of CNC parts to heat-treated or cooled. The smooth surface achieved increases fluid flow efficiency and improves heat transfer.
  • Improved hygiene: it is instrumental in the food, pharmaceutical and medical industries, where high hygiene standards are required. The process removes contaminants and microorganisms from the surface, minimizing the risk of contamination.
  • Precision finishing of details: the electropolishing procedure allows precise finishing of even the most complex shapes. As a result, the CNC company can achieve high quality and accuracy in surface finishing.
  • Reduced machining time: Electropolishing is faster than traditional surface finishing methods. This process can reduce machining time, increasing efficiency and production output.
  • Cost reduction: with electropolishing, you can reduce production costs. The process requires less manual labor and reduces machining time, which can translate into savings for your CNC company.
  • Competitiveness in the market: Using electropolishing can differentiate your CNC company. With better quality and aesthetic parts, the company can attract new customers and build its reputation as a supplier of quality products.

What are the disadvantages of electropolishing? 

Electropolishing, despite its many advantages, also has some disadvantages that are worth knowing:

Cost: Electropolishing is expensive, especially compared to other surface finishing techniques. The cost alone is the equipment and the chemicals used throughout the process. 

Safety: The electropolishing process requires highly acidic or alkaline solutions, posing health and safety risks to workers. 

Material limitations: Electropolishing is most effective for highly conductive metals, such as stainless steel, copper, and aluminum. Some materials, especially non-metals, may not be suitable for electropolishing.

Process control: Unfortunately, this process is complicated and requires precise control of temperature, voltage, and exposure time. Without a doubt, it requires experience and technical expertise.

Chemical waste: The electropolishing process generates chemical waste that must be properly neutralized and disposed of. 

Despite these drawbacks, electropolishing is still widely used because of its unique advantages, such as its ability to smooth hard-to-reach areas and improve corrosion resistance. However, it is a process best outsourced to professionals with the right equipment and experience.

Electropolishing versus other surface finishing methods

Electropolishing is one of many surface-finishing techniques used in the CNC industry. It is an electrochemical process that removes small amounts of material from the surface of a workpiece, resulting in a smoothed and polished surface. It is often used to remove sharp edges, coarsening and other imperfections during machining.

However, electropolishing is not the only surface finishing technique used in CNC. There are also other methods, such as: 

  • grinding, 
  • laser engraving, 
  • powder coating, 
  • anodizing, and many others. 

Each of these techniques has unique benefits and applications, and the choice between them often depends on the project's specific requirements.

For example, grinding is often used to remove large amounts of material and can be used to create very smooth and uniform surfaces. On the other hand, laser engraving is often used to create precise patterns and details on the surface of a part.

Powder coating and anodizing add color to a workpiece or increase its corrosion resistance.

Compared to these techniques, electropolishing offers unique advantages, such as: 

the ability to smooth and polish hard-to-reach areas, 

the ability to improve corrosion resistance by removing minor surface imperfections.

However, like any technique, electropolishing has limitations and is not always suitable for every application. The decision on the appropriate surface finishing method should always consider a project's specific requirements and limitations.

The future of electropolishing 

The use of advanced electropolishing technologies in CNC, the application of new materials, the development of sustainable manufacturing, personalization and aesthetics, cross-sector collaboration, and automation and integration into production systems are key trends shaping the future of this efficient and versatile surface treatment process. 

Innovative technologies, such as advanced control systems, intelligent algorithms, and artificial intelligence, enable, or will enable, over time, fine-tuning of electropolishing parameters. At the same time, electropolishing in CNC can contribute to sustainable manufacturing by reducing energy consumption, reducing the use of non-organic chemicals, and increasing the durability and longevity of products. The personalization and various aesthetic effects offered by electropolishing allow the creation of unique value-added products. In addition, the sharing of knowledge and cross-sector innovation, as well as integration with CAD/CAM and CNC systems, contribute to the further development of electropolishing, increasing precision, repeatability, and reduced production cycle times. As a result, electropolishing in CNC represents a promising future, improving product efficiency, quality, and attractiveness. Let's face it - electropolishing is an effective tool that can benefit manufacturers and CNC specialists. Improved product quality, durability, and performance are just some of them. It's a simple and effective solution for companies that want to keep their products in top condition for as long as possible.