Dairy, food, and beverage processing plants, breweries, pharmaceuticals, and other sectors that involve sanitary processing require specific stainless steel surface finishes to comply with regulations. Imperfections on the surfaces or edges of the equipment can harbor contaminants and bacteria, making thorough cleaning difficult. Stainless steel is the preferred material for fabricating the processing equipment for these industries because it is possible to achieve a smooth surface finish in a cost-effective manner.
Understanding Surface Finish Requirements
There are multiple factors used in determining the quality of a surface finish. Here are the technical terms used for describing surface finishes:
- Grit describes the size of the abrasive used for mechanical polishing. The higher the grit value, the finer the polishing material. Grit value is proportionate to the quality of the finish it can provide.
- Roughness average (RA) refers to the average heights of the peaks and depths of the valleys on a metallic surface. These peaks and valleys are microscopic, so they are measured in microinches or micrometers. A smoother surface yields a lower RA value.
- Root mean square (RMS) measures the area of the heights and depths of imperfections on the metal’s surface. Like RA, a lower RMS value indicates a smoother surface.
RA is the more widely used measurement, since a single outlier imperfection can skew the RMS value. RA is measured with a profilometer—also known as an RA meter—that calculates RA by simply averaging the variations on the metal’s surface. Profilometers are useful for measuring and recording finishes of equipment such as process piping and stainless steel tank surfaces. The printed record of the RA value is proof of compliance with regulations.
Highland Equipment’s Finishing Services
There are several methods available for polishing stainless steel. As an industry-leading supplier of stainless steel equipment, Highland Equipment uses both electric and mechanical polishing methods to achieve RA values in the 5–32 range.
Mechanical polishing is an abrasive finishing method that uses particles with grit values of 120 or higher. Mechanical polishing can be followed with electric polishing to make equipment suitable for use in these environments.
Electric polishing, also called electropolishing, uses electric current in conjunction with a chemical bath to strip the surface layers of the metal. Electropolishing gives the metallic substrate a mirror-like finish and high level of smoothness that make the surface easy to clean. The primary benefits of electropolishing include:
- Improved corrosion resistance caused by passivating the metallic surface.
- An excellent finishing step after mechanical polishing, since electropolishing smooths out any imperfections imparted by abrasive media.
- A superior reflective appearance and excellent finished surface.
Highland Equipment has been in the business of designing, manufacturing, and installing high-quality stainless steel equipment for more than 45 years. Our customers in the cannabis, cosmetics, dairy, food and beverage, and pharmaceutical industries trust us to supply and maintain a broad range of sanitary stainless steel equipment.
Contact us to discuss our capabilities and how we can help fulfill your requirements for sanitary stainless steel equipment.