Electropolishing: Myths and Realities

A. Villafranca y W. Barrales

Electropolishing, as another process of treatment for metallic surfaces, stands out against others for its effective reduction of micro rugosities, which translates to a smooth touch, a surface with minimal adherence and low susceptibility to the harboring of contaminants. This process is very useful in different industries, like the pharmaceutical and food industries, and even for urban furniture, thanks to the qualities that electropolished stainless steel provides.

In the pharmaceutical industry, where substances have to maintain maximum purity and any risk of contaminants must be eradicated, electropolishing is a solution for that requirement. Another example can be seen in the food industry, where extracts that contain higher levels of acidity reduce the service life of stainless-steel installations; in these cases, electropolishing can represent an excellent option to enhance the surface resistance to corrosion, in comparison to a standard polished surface.

Are you interested in knowing more about our electropolishing process and its benefits? Visit our section Electropolishing | OGMAN.

The result of passivating a surface compared to electropolishing it, presents significant differences between the two (read our article Passivation vs. Electropolishing). For the latter, besides a chemical bath, it incorporates the use of electrical current during the process, achieving so much more than passivation. Although both processes have the goal of keeping the installation free of contaminants and corrosion, electropolishing adds the quality of resulting in a flat and smooth surface, apart from prolonging the material’s service life. Nevertheless, it’s always important to know the use and application the fittings, tubing or pieces to be electropolished, in order to recommend the treatment and finish that best fit the needs of that process or industry. For this reason, we’ll tackle and clarify some of the most popular myths about electropolishing.

Myth: Electropolishing is useful to eliminate scratches

It’s commonly believed that electropolishing can remove scratches on a surface because it’s associated with its capacity to smooth down a surface. However, this is FALSE. Electropolishing isn’t a coating, such as galvanizing or chrome plating, but a surface treatment that — instead of filling — removes material.  If the piece or tubing to be electropolished has scratches or fissures, it’s very likely that they will become more noticeable after the application of the process.

Prior to performing an electropolish, a mechanical polish could be done (if the gauge of the material and the measurement tolerances allow it), a process that can help eradicate superficial imperfections.

As it can be seen in the image, scratches and defects might seem minimal with a mechanical polish. However, the benefit of a mechanical polish will depend on the depth of the imperfection and the gauge of the material to be electropolished. 

Myth: Electropolishing increases rugosity 

When carrying out mechanical polishing and changing from a coarse abrasive grain to a fine one, the crests generated form the first abrasive will only be bent and smeared by the second one; that is to say, they won’t be polished correctly. Electropolishing a surface polished this way causes the current to concentrate on the bent crests, dissolving them along with the smeared material and digging up the original profile, that is only partially rounded, ending up in a higher reading on the roughness meter.

For this reason, it’s believed that electropolishing increases rugosity, however, it isn’t a result from the electropolishing process, but a consequence from a badly executed mechanical polish, therefore this myth is FALSE. With a well-executed mechanical polish, a lower surface rugosity can be achieved at the end of the process.

Myth: Electropolishing will always leave a mirror-like finish.

FALSE. Electropolishing doesn’t always end with a mirror-like finish. Actually, depending on the type of steel and its composition, it can result in a low esthetic finish (industrial electropolish), however, this doesn’t mean that the results and the benefits of the treatment haven’t been obtained. The scope can always be tested through a prior analysis of both the material and the needs of each customer.

Other factors that can lead to an opaque finish, are the type of metal or the previous surface polish. A bright mechanical polish, a sandblast or a 400 series steel can result in an opaque finish after electropolishing. Therefore, if you ignore the characteristics of the material you wish to electropolish, you can reach out to us and request more information, or a sample electropolish. We’ll be happy to help you!

Myth: Interior electropolishing can make any tubing suitable for pharmaceutical use 

Electropolishing does not, under any circumstances, replace the type of steel or the standard it was manufactured under, so this myth is FALSE. The applicable standards for each industry require compliance of additional conditions apart from the finish of the material. For example, ASME-BPE tubing cannot be replaced with 304 tubing with interior electropolishing. Electropolished tubing that only meets the A269 standard cannot replace tubing whose characteristics require they meet the A270 standard, and so on.

ASME-BPE Tubing used in the pharmaceutical industry cannot be replaced with 304 tubing with interior electropolishing.

In summary, electropolishing is always profitable and useful to increase the service life of production equipment in any process, even in installations that already follow strict quality standards. It’s important to realize the long-term investment that is made by using electropolished equipment and fittings but, above all, to have the certainty of carrying out the service with a specialist in the field.

At OGMAN we work under certified quality standards and our specialized personnel can help you get the results you need from electropolishing. We team up with you to find solutions to the demands of your industry.  

Any questions? Reach out to us!