Electropolishing is a metal smoothing method similar to polishing. However, in practice, it is more advanced. Electropolishing is most commonly used for stainless steel and other similar metals. Thanks to this process, the surface becomes shiny, smooth, and aesthetic. Many people confuse electropolishing with passivation, but each of these processes is a completely different activity. In practice, each of them helps the metal to better cope with corrosion, but in principle - only electropolishing uses electric current. Additionally, electropolishing makes the metal surface less rough, even by half. Electropolishing is a great process well suited for delicate metal items or those with a complex shape. It works similarly to reverse galvanization. Instead of applying a thin layer of metal, electropolishing uses electric current. Despite the fact that there is a lot of discussion in the world of metallurgy about the effectiveness of electropolishing in combating corrosion, it is certainly a process worth knowing and using if you want to achieve an exceptionally smooth and clean metal surface.
Aluminum, and electropolishing
Aluminum is now more frequently used in the CNC industry. This is due to the fact that this product is cheap, easy to process, and lightweight. But the problem is its finish. Electropolishing helps to 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 rooms, for example in laser devices.
We distinguish two main types of aluminum:
- cast alloys
- product for plastic processing.
Cast alloys can be easily melted, but they have a worse finish. Alloys for plastic processing are different - electropolishing of this type of aluminum has a smooth surface without impurities. In the case of aluminum - electropolishing involves passing an electric current through aluminum in a special solution. The current causes the dissolution of irregularities on the surface of the aluminum, making it smooth.
It is important to use appropriate chemical agents during electropolishing. Traditionally, perchloric acid is used, but it has problems related to safety and environmental protection. An alternative is the so-called deep eutectic solvents (DES), which are less dangerous for people and the environment. It is also worth noting that electropolishing of aluminum has many advantages, such as increased corrosion resistance, better surface finish, ease of cleaning, nice appearance, and longer part life.
Advantages of electropolishing aluminum
Why is electropolishing of aluminum used? This is due to the fact that corrosion most often starts from the surface of this metal. Unfortunately, various processes related to production can worsen the condition and properties of the aluminum surface. For example, it can be pointed out that during welding, machining or other production processes, various contaminants, such as metal particles, iron, dirt or grease, can settle on the surface of aluminum. Mechanical polishing, cutting or other processing can lead to the deposition of foreign iron particles or other abrasive substances. These contaminants can destroy the natural layer of aluminum oxide, which protects against corrosion. In case of its damage, the corrosion process begins. The solution to the problem is electropolishing. This process involves dissolving a thin layer of the aluminum surface along with contaminants. This removes deposited particles, which in turn increases the durability of the element. However, let's not forget that electropolishing of aluminum also has other benefits. The surface after such treatment becomes more resistant to corrosion, looks better, is less sticky and easier to clean. In addition, electropolishing helps to remove irregularities, giving aluminum an attractive appearance. An additional bonus is the fact that electropolished aluminum is more resistant to various types of corrosion, such as pitting, galvanic, surface, crevice, as well as cracking, stress corrosion and microbiological.
What is chemical-mechanical polishing?
Chemical-mechanical polishing, also known as CMP, is a process in which the top surface of a plate is polished using a suspension. The above suspension contains special grains, which in combination with the appropriate chemistry lead to the abrasion of the product layer. This means in practice that the process consists of a chemical and mechanical part.
- The mechanical aspect involves downward pressure.
- The action of chemistry helps accelerate material removal.
The speed of the process depends on the type of material being processed.
Application of electropolishing in practice
Electropolishing has been a method used since the 1950s. As we mentioned earlier, the process itself works in two ways: mechanically and chemically. Most often, such products are used in industries such as:
- Medicine: Surgeons and dentists use electropolishing to keep their tools clean and efficient.
- Food and pharmaceutical industry: Takes advantage of the sterilizing properties of electropolishing.
- Home appliance manufacturing: Electropolishing enhances the durability and aesthetics of components in devices such as refrigerators or washing machines.
- Aviation industry: This sector uses electropolishing on key aircraft parts to minimize friction and maximize performance.
- Semiconductor production: Utilizes electropolishing for precise processing of delicate products with irregular shapes.
- Automotive industry: Car manufacturers and the racing sector use electropolishing on parts such as gears or fuel lines, which helps in reducing friction, improving performance, and extending the lifespan of parts.
Electropolishing is often used for the treatment of elements such as:
- Pipes and tubes
- Connecting elements
- Springs
- Wire racks
What is stainless steel electropolishing?
Similar to the case of aluminum - thanks to electropolishing, stainless steel becomes smooth, shiny, and free from impurities, which further increases its resistance to corrosion. Although this process can be applied to various metals, the most commonly used are alloys of 300 and 400 series stainless steel. The 400 series stainless steel offers better hardness and durability, but is more prone to corrosion - electropolishing allows maintaining these features while simultaneously increasing corrosion resistance. Other example metals that undergo the electropolishing method are the previously mentioned
aluminum, brass, carbon steel, cobalt chrome, copper alloys, nickel alloys, titanium and nitinol. However, it's worth remembering that electropolishing is not always effective for cast metals, for example, those that contain a lot of silicon, sulfur or carbon.
Electropolishing of copper
Electropolishing of copper is a process that begins with cleaning the metal surface using an appropriate chemical solution. Then, the copper is immersed in an electrolytic bath with the addition of sulfuric or hydrochloric acid, and the application of 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, which facilitates its cleaning and prevents the accumulation of dirt or bacteria. Another aspect is the fact that this process extends the lifespan of metal elements. Therefore, electropolishing can improve the efficiency of production processes thanks to 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 elements. The advantages of this technology are as follows:
- Aesthetic improvement: Electropolishing can significantly improve the appearance of metal elements. This process removes irregularities, scratches, and other surface defects, giving metal elements a smooth and shiny surface.
- Removal of oxides and impurities: The electropolishing process removes oxides, rust, deposits, and other impurities from the surfaces of metal elements. This process ensures cleanliness and improves the durability of the elements.
- Improvement of corrosion resistance: Electropolishing creates a layer of oxides on the metal surface, which protects the elements from corrosion. This additional protective layer is particularly useful in the case of elements exposed to weather conditions and aggressive environments.
- Fluid flow optimization: the electropolishing process can improve the quality of CNC components that are to undergo heat treatment or cooling. The smooth surface obtained as a result increases the efficiency of fluid flow and improves heat exchange.
- Improvement of hygiene: it is particularly useful in the food, pharmaceutical, and medical industries, where high hygiene standards are required. This process removes contaminants and microorganisms from surfaces, minimizing the risk of contamination.
- Precise finishing of details: the electropolishing process allows for precise finishing of even the most complex shapes. This allows the CNC company to achieve high quality and accuracy of surface treatment.
- Limited processing time: Electropolishing is faster than traditional surface finishing methods. This process can reduce processing time, which translates into efficiency and increased production output.
- Cost reduction: thanks to electropolishing, you can reduce production costs. This process requires less manual labor and shortens processing time, which can result in savings for the CNC company.
- Market competitiveness: Utilizing electropolishing can differentiate your CNC company in the market. With better quality and aesthetics of components, the company can attract new customers and build its reputation as a supplier of high-quality products.
What are the disadvantages of electropolishing?
Electropolishing, despite its many advantages, also has some disadvantages that are worth knowing:
- Cost: Electropolishing is a costly process, especially when compared to other surface finishing techniques. The costs include not only the equipment, but also the chemicals used throughout the process.
- Safety: The electropolishing process requires the use of highly acidic or alkaline solutions, which poses a risk to the health and safety of workers.
- Material limitations: Electropolishing is most effective for metals that are good conductors, such as stainless steel, copper, or aluminum. Some materials, especially non-metals, may not be suitable for electropolishing.
- Process control: Unfortunately, this process is quite complex and requires precise control of conditions such as temperature, voltage, and exposure time. Without a doubt, this requires experience and technical knowledge.
- Chemical waste: The electropolishing process generates chemical waste that must be properly neutralized and removed.
Despite these drawbacks, electropolishing is still widely used due to its unique advantages, such as the ability to smooth hard-to-reach places and improve corrosion resistance. However, it is a process that is best entrusted to professionals who have the appropriate 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 part, leading to smoothing and polishing of the surface. It is often used to remove sharp edges, burrs, and other imperfections that may occur during mechanical processing.
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 its own unique benefits and applications, and the choice between them often depends on the specific requirements of the project.
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 are used to add color to a detail or increase its resistance to corrosion.
Compared to these techniques, electropolishing offers unique benefits, such as:
- the ability to smooth and polish hard-to-reach areas,
- possibility of enhancing corrosion resistance by removing minor surface imperfections.
However, like any technique, electropolishing has its limitations and is not always suitable for every application. The decision on choosing the appropriate surface finishing method should always consider the specific requirements and limitations of the given project.
The future of electropolishing
The use of advanced electropolishing technologies in CNC, the application of new materials, the development of sustainable production, personalization and aesthetics, cross-sector cooperation, and automation and integration into production systems are key trends shaping the future of this effective and versatile surface treatment process. Innovative technologies such as advanced control systems, intelligent algorithms, and artificial intelligence enable or will eventually allow for precise adjustment of electropolishing parameters. At the same time, CNC electropolishing can contribute to sustainable production by reducing energy consumption, limiting the use of non-ecological chemical substances, and increasing the durability and longevity of products. Personalization and various aesthetic effects offered by electropolishing allow for the creation of unique products with added value. In addition, the exchange 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 shortening the production cycle time. As a result, CNC electropolishing represents a promising future, improving the efficiency, quality, and attractiveness of products. Let's be honest - electropolishing is an effective tool that can benefit both manufacturers and CNC specialists. Improving the quality, durability, and performance of products are just some of them. It's a simple and effective solution for companies that want to keep their products in the best condition for as long as possible.