The difference between an electropolished surface and a non-electropolished surface

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Stainless steel is more than just a corrosion resistant metal. Stainless steel is often chosen as a general purpose material for many applications due to its strength, corrosion resistance, as well as its ability to adapt to specific conditions.

Product Specification and Steel Grade (For Reference)

Tolerance of Width

Chemical Composition & Mechanical Property

Chemical Composition (For Reference)

ASTM Specification

Mechanical Property (For Reference)

ASTM Specification

This applies not only to the various chemical compositions that make up stainless steel, but also to the various surface finishes and treatments that may be applied depending on the end intended use of the product.
Grade 2B is one of the most commonly used surface treatments in the stainless steel industry. It is semi-reflective, smooth and uniform, though not specular. The surface is the last step in the process; the steel sheet is first formed by pressure between the rolls as it exits the furnace. It is then softened by annealing and then re-passed through rolls.
To remove surface contaminants, the surface is acid-etched and passed between polishing rollers several times to achieve the desired thickness. It is this last hurdle that makes the completion of 2B possible.
2B is the standard finish on common stainless steel grades including 201, 304, 304 L and 316 L. What makes the 2B finish popular, besides being economical and more corrosion resistant, is the ease of polishing with a cloth wheel and compound.
Typically, 2B finish steel is used in food processing, bakery equipment, containers, storage tanks, and pharmaceutical equipment, and it meets USDA standards for these industries.
This approach is not acceptable when the final product is an injectable or otic solution. This is due to the fact that there are gaps or pits on the metal surface. These voids trap contaminants under the polished surface or in the metal. Eventually, this foreign matter can come out and contaminate the product. Surface electropolishing is the ideal and recommended method for improving surface smoothness for such applications.
Electropolishing works by using chemicals and electricity to smooth out raised areas on stainless steel surfaces. The actual surface of stainless steel does not appear smooth when magnified, even though the factory applied a smooth 2B surface.
Average Roughness (Ra) is used to refer to the smoothness of a metal surface and is a comparison of the average difference between the lowest and highest points on the surface.
Typically, fresh polished 2B stainless steel has a Ra value ranging from 0.3 micron (0.0003 mm) to 1 micron (0.001 mm) depending on its thickness (thickness). Surface Ra can be reduced to 4-32 micro inches with proper electropolishing, depending on the specification of the metal.
A class 2B finish is achieved by compressing the material with two rollers. Some operators require surface repairs after modifications or repairs to the boat or other equipment.
While the surface finish done by mechanical or electropolishing cannot be easily reproduced, it is possible to get very close to it, especially in terms of Ra values. Proper electropolishing results in even better material handling than the original raw 2B polish.
So class 2B can be seen as a good starting point. Thanks to its well-known beneficial properties, 2B surface treatment is economical. It can be further enhanced with electropolishing for a smoother finish, higher standards and a range of long-term benefits.
This information has been obtained, verified and adapted from materials provided by Astro Pak Corporation.
Astro Pack Corporation. (March 7, 2023). The difference between electropolished and non-electropolished surfaces. AZ. Retrieved June 13, 2023 from https://www.azom.com/article.aspx?ArticleID=22050.
Astro Pack Corporation. “The difference between electropolished and non-electropolished surfaces”. AZ. June 13, 2023 .
Astro Pack Corporation. “The difference between electropolished and non-electropolished surfaces”. AZ. https://www.azom.com/article.aspx?ArticleID=22050. (As of June 13, 2023).
Astro Pack Corporation. 2023. The difference between electropolished and non-electropolished surfaces. AZoM, accessed 13 June 2023, https://www.azom.com/article.aspx?ArticleID=22050.
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