Paul Mueller Company Academy

Finding the Right Finish: Understanding Polishing

August 4, 2022 | by Paul Mueller Company Service Team


Stainless steel is a strong, corrosion-resistant alloy that contains chromium and other elements in various combinations. Manufacturers use it for countless applications and products, including stainless-steel tanks, in many industries. They include beverage production, brewing, dairy processing, HVAC, oil & gas production, pharmaceutical manufacturing, and several others.

For some uses, companies can put products into service as soon as they come off the production line. However, in other instances, it is best if the company that creates a stainless tank for brewing, for example, goes a step further and polishes it.

Polishing a storage tank or other item is a physical process that removes material from a stainless-steel surface. Polishing process equipment produces multiple benefits, including increasing the surface’s resistance to corrosion, wear, and other environmental factors. As a result, it lengthens the service life of storage tanks and other products. Polishing also improves the appearance of stainless steel, enhancing its smoothness, uniformity, and shine. 

The fact that manufacturers can improve stainless steel in this way surprises some people. However, while stainless steel has tremendous strength and durability, it isn’t impervious to corrosion and damage. Polishing enhances stainless steel’s natural characteristics to make it an even better material for manufacturing.

The Polishing Process

Manufacturers polish stainless steel by applying various grades of abrasive media (sometimes referred to as grit strength) to the surface. Typically, they do this in steps from coarse to fine abrasion.

This process removes impurities and also minimizes or removes tiny cracks or crevices that can harbor bacteria or other harmful contaminants. In doing so, polishing can ensure that stainless-steel tanks meet specific customer or governmental requirements, including 3-A sanitary standards.


10 Common Material Finishes

Paul Mueller Company has extensive experience in polishing stainless-steel process tanks and other products. That includes offering 10 different material finishes to accommodate any type of use. Material finish names are not industry standard, so it is always recommended to reference your needed Roughness Average (Ra) when specifying equipment finish requirements. 

  1. Hot rolled (HR) finish. A hot rolled finish results in a rough and dull appearance on the material’s surface.
  2. 2B mill finish. This finish features a smooth, bright, moderately reflective appearance suitable for “as-is” specifications or we may achieve it as a preliminary finish for further polishing.
  3. #3 finish. We create this finish using the equivalent of an 80-grit abrasive. It has a pronounced grit line and a 75 Ra average.
  4. #4 finish. This is a bright finish with visible grain for use where sanitary surfaces are required. It has a 35 Ra target, but customers can request a 32 Ra maximum finish to comply with 3-A standards.
  5. #6 finish. This finish has a 25 Ra target that we achieve with the equivalent of a 240-grit abrasive. It results in higher reflectivity, finer grit lines, and improved product release and cleanability.
  6. #7 finish. If a customer’s product has critical product contact surfaces and requires minimal grit lines, they typically need this type of finish. We achieve it using the equivalent of a 320-grit abrasive.
  7. Bead blast. This process follows sandblasting to create a satin, gray appearance that resembles a 2B finish.
  8. Radial spin polish. We use this process on preformed inside, outside, knuckle, and straight flange surfaces. It follows a circular pattern and produces an aesthetically pleasing sanitary finish.
  9. Circumferential spin polish. This process is similar to radial spin polishing. It further reduces the visibility of the circular pattern. Circumferential spin polish creates a premium finish for high-visibility tanks.
  10. Sheet polish. In this process, stainless-steel material is polished as sheets prior to forming. The formed items can be produced at a lower cost but will have a finish that shows things like visible weld lines. In some instances, follow-up spin polishing may be needed to address incidental damage during the manufacturing process. Even so, the surface retains its Ra.

These common finishes and processes meet most customer needs for products like process equipment, steel tanks for brewing, storage tanks, etc.

Learn More About Stainless Steel Polishing

Few materials can compare to polished stainless steel’s strength, durability, and cleanliness characteristics. It is an excellent material for stainless-steel process tanks and storage tanks.

If you have questions about how polishing can ensure your stainless-steel products meet applicable functional and visual standards, we’re happy to answer them. Please contact us at your convenience.

About Paul Mueller Company Academy

Teaching and sharing ideas has long been part of the rich heritage at Paul Mueller Company. We have almost a century of quality craftsmanship guiding the way we apply new learnings. Paul Mueller Company Academy is a collection point for those learnings, so we can collaborate and grow more successful together. You will find articles, blogs, guides, infographics and more dedicated to furthering knowledge for all, in the world of stainless steel processing equipment solutions. We hope you enjoy!