{"id":21961,"date":"2023-08-22T15:32:20","date_gmt":"2023-08-22T12:32:20","guid":{"rendered":"https:\/\/fractory.com\/?p=21961"},"modified":"2024-01-26T13:12:10","modified_gmt":"2024-01-26T11:12:10","slug":"electropolishing-explained","status":"publish","type":"post","link":"https:\/\/fractory.com\/electropolishing-explained\/","title":{"rendered":"Electropolishing Explained – How It Works, Benefits & More"},"content":{"rendered":"

When metallic components come out of manufacturing or fabrication, they generally require some type of surface finishing process<\/a> to improve their appearance or corrosion resistance properties.<\/p>\n

Sometimes, these treatments may also improve the electrical or mechanical properties<\/a> of the part. This is an important stage in manufacturing and can have a significant effect on the durability and functionality of a part.<\/p>\n

In this article, we cover one such process: electropolishing. We shall explore what it is, how it works and its advantages over other treatment methods. Let\u2019s begin.<\/p>\n

What Is Electropolishing?<\/h2>\n

Electropolishing, or anodic polishing, is an electrochemical process that uses electricity to remove a thin layer from the surface of electrically conductive metals.<\/strong> The removal of this thin layer improves the metal’s surface roughness as well as its corrosion resistance. The finished products look shiny and clean as the discolouration and\/or embedded foreign materials from previous processes are eliminated.<\/p>\n

Electropolishing can remove up to 40 micrometres from a surface, depending on the process parameters. But typically, electropolishing is used to remove between 8 and 20 micrometres.<\/p>\n

There are applications where a very small amount of metal removal is necessary. Hypodermic needles are a good example. For such parts, a flash electrolytic polishing process can deburr edges<\/a> and passivate the parts using a small amount of current and a short process duration.<\/p>\n

The percentage of surface finish achieved depends on the initial finish. Up to 50% Ra (Roughness average) reduction is possible through electropolishing. But due to practical limitations, we can usually achieve between 25 and 40%.<\/p>\n

However, as the Ra value becomes smaller, we get a diminishing rate of return. This means that a well-finished part will not be able to benefit in the same manner from electropolishing as a relatively rougher part. For instance, if we were to electropolish a metal surface that has Ra value of 10\u201315, we would only be able to achieve a reduction of about 10 percent.<\/p>\n

The electropolishing process is also frequently used as a secondary finishing process to supplement mechanical polishing. Where mechanical polishing methods remove macroscopic surface imperfections, electropolishing removes microscopic surface imperfections.<\/p>\n

For example, a 70 Ra part can benefit by about 40% if we were to use electropolishing right away, bringing the final Ra value to about 40. But we can use mechanical polishing first and reduce the Ra value to 40, followed by a 40% reduction from electropolishing to achieve a final Ra of about 20\u201325.<\/p>\n

How Does the Electropolishing Process Work?<\/h2>\n
\"Electropolishing
1 – Electrolyte, 2 – Cathode, 3 – Anode (workpiece), 4 – Particle moving from the workpiece to the cathode, 5 – Surface before polishing, 6 – Surface after polishing<\/figcaption><\/figure>\n

 <\/p>\n

The electropolishing process works on the principle of an electrolytic cell. In the electropolishing process, we connect the workpiece to the positive terminal of the cell and make it the anode.<\/p>\n

A suitable metal connected to the negative terminal becomes the cathode. The cell in this case is usually a DC rectifier that converts AC supply to DC supply at the output.<\/p>\n

Let us understand the electropolishing process by dividing it into three distinct stages. These are:<\/p>\n

    \n
  1. \n

    Surface preparation<\/p>\n<\/li>\n

  2. \n

    Electrolytic polishing<\/p>\n<\/li>\n

  3. \n

    Post-treatment<\/p>\n<\/li>\n<\/ol>\n

    Surface Preparation<\/h3>\n

    Electropolishing requires a clean surface to enable a uniform electrical current. Contaminants cause uneven current density that will lead to uneven surface erosion.<\/p>\n

    But the surface can collect contaminants from previous processes or part handling in the shop. These could be grease, oil, shop dirt, fingerprints or any films left on the part after manufacturing. The amount of contaminants directly determines the final finish quality.<\/p>\n

    Thus, the first step is to thoroughly clean the surface of all contaminants. The cleaning process begins with an alkaline and solvent cleaner, followed by pickling<\/a>. After each process, the part is rinsed to remove the process residues.<\/p>\n

    Electrolytic Polishing<\/h3>\n
    \n
    \n
    \n<\/span>