What is the difference between Electropolishing and Passivation?

When incorporating metal into a product, one of the most essential steps to consider is that of the final finish bestowed upon the metal’s surface. In most cases, especially when working with steel, one will choose to polish the workpiece. This process can be controlled to have a wide range of finishes. Some prefer a dull polish, as is provided by either polishing to a satin finish or by brushing; others would rather incorporate a bit of a shine, giving the metal a nice, bright mirror finish. Both can look aesthetically pleasing, but a bright, highly-polished finish will ensure that the metal will produce less friction and remain durable over time.

In addition to polishing, one may elect to take an additional step and passivate the metal workpiece.

Both electropolishing and passivation work to remove any potential contaminants from the surface of the metal, thereby preventing it from degrading prematurely. They also both work to sterilize the metal surface and mitigate further contamination and corrosion that may occur in the future.

To those unfamiliar with the processes, electropolishing and passivation might sound quite similar, and, although they work together toward the same goal, they are strikingly different. Want to learn more? Here is the breakdown for anyone interested in purchasing metal finishing solutions:

Electropolishing

During the electropolishing process, the product is placed into a temperature-controlled electrolyte bath and exposed to an electric current. This exposure causes the metal surface to ionize and begin dissolving into the electrolyte solution, starting at any exposed metal burrs. As this leaves the surface microscopically-smooth and sterile, electropolishing is a favored process in the production of metal for the pharmaceutical and food industries.

It is a scientific principle that smooth surfaces create less friction than rough surfaces. When applied to metal machinery, this translates into a product with greater durability and efficiency that will last longer than products without an electropolished finish. This smooth surface is incredibly valuable in the manufacturing of any consumer machinery, such as washing machines, or in aerospace and automotive engineering, as in the body of a car or passenger plane.

As an electropolished piece has very minimal dents and divots, it is extremely easy to clean. This feature is highly valued in clinical and dental environments, where metals must be sterilized.

From a visual standpoint, electropolishing can completely remove any heat spots or other forms of discoloration caused by the manufacturing process.

High performance electropolishing

The ingredients used in electropolishing solutions vary with the metal intended to be polished, meaning you can manufacture a chemical solution for the electropolishing of stainless steel that is specifically designed for a high-performance finish on stainless steel products – we even have options for 300 Series Austenitic (non-magnetic) stainless steel and 400 Series Martensitic stainless steel. If you have another metal such as copper, nickel, or iron, a different solution is available to ensure the metal receives the best possible finish.

Large and complex metal finishing

Lots of companies are now opting to use electropolishing to finish their products due to its application on metals of all sizes and complexities. Electropolishing tanks (containers used to hold the electropolishing solution) can be designed for all shapes and sizes and allow for partial or complete submersion of the metal’s surface during the polishing process. Whether you’re working with nuts, screws and needles, large sheet metals, or metals with narrow channels and difficult to reach areas, an electropolishing bath is an easy-to-implement option for your manufacturing process.

Passivation

Passivation is much like electropolishing in that it also uses a chemical bath. However, rather than stripping away metal from the surface of a workpiece, passivation is the process of treating or coating a metal surface to reduce its chemical reactivity.

Unlike electropolishing, passivation is not designed to remove material from a metal surface and does not change the appearance of the metal. As a result, passivation will not necessarily make a product non-stick or make it easier to clean. It will look and feel much like what it did before passivation was carried out.

Which Is Best?

Although both passivation and electropolishing employ a chemical bath, they may be thought of as being complementary to each other, rather than the same process. Electropolishing causes the metal workpiece to be stripped down, cleaned, sterilized, and altered on the surface to prevent future damage and contamination. Passivation skips the metal stripped and sterilization, focusing solely on removing contaminants and altering the outside layer to prevent chemical reactions from occurring on the metal’s surface.

Electropolishing produces a product that is much more visually appealing and easier to clean. Additionally, although it includes more steps in the process, it is the faster option as well and can be used on a wide range of metals. Passivation is used most often on stainless steel.

When making your decision, you will need to consider what type of metal you would like treated and how the final product will be used. Once you’ve thought of these two factors, then you will find the decision a lot easier to make.

To find out more about our electropolishing chemical solutions you can request a Safety Data Sheet, or Technical Data Sheet for any of our products, or Request a Quote today.