The process for sanitary stainless steel equipment fabrication starts with the selection of the metal and special handling of the material to prevent contamination. For many food and chemical producers, the level of finishing on processing equipment is determined by federal, state, and local regulatory agencies. In sanitary applications, the finish, as well as the material, must be designed to mitigate risk and allow for effective and efficient cleaning and sanitation.
A bead blast finish is commonly used for exterior equipment surfaces and can be found on the interior food contact surfaces. The bead blasting process utilizes bead material such as glass or ceramic beads to produce a non-directional, textured surface with a soft satin appearance and low reflectivity. The finer the blasting media, the more corrosion-resistant the surface performance. The RA values are typically higher than 45 but are dependent on the blasting process and the stainless material.
Bead blasting is commonly used when a uniform finish is desired in structural, material handling, or food handling applications. Many food manufacturers utilize a bead blast finish on the food contact surface area; all who have the equipment and sanitation protocols that comply with their industry food safety regulations.
Electropolishing is an electrochemical process that removes surface material from stainless steel. It produces an extremely smooth, mirror-like finish. The process includes immersing the stainless-steel component into a temperature-controlled bath of electrolytes charged with a DC power supply. Electrolytes used in electropolishing are concentrated sulfuric and phosphoric acid solutions.
Electropolished food contact surfaces comply with sanitation protocols, provide operational sanitation performance beyond compliance, and significantly reduce food attachment, which drives food safety goals and sanitation efficiencies for food processors.
Under 200X magnification, the 304 Stainless electropolish finish shows six times the smoothness measurement than the 304 Stainless Bead Blast Finish.
As microorganisms attach to surfaces, they become more resistant to both physical and chemical sanitation practices. It was determined that out of eleven different finishes tested, the electropolished finish was the most resistant surface to bacterial attachment.
Electropolished food contact surfaces commonly optioned in Mepaco’s cookers, mixers, pump feeders, vacuum stuffers, screw conveyors and inside chutes of dumping equipment. Agitators, shafts and augers can also be electropolished, to treat the entire food contact surface. Electropolishing services are offered in-house by experienced technicians; there is no dependency on outsourcing.
Mepaco’s food processing customers have more discretion in choosing equipment finishes, even in food contact environments. The type of food product, bacterial count, manufacturing function, and sanitation procedures all have an impact on the requirements of equipment finishes.
In terms of material used in food processing and commercial equipment, here is the list of stainless materials from smoothest to the roughest RA range.
Electropolished surfaces range from 6 RA – 14RA microinches. Electropolishing can change RA values up to 50% smoother, depending on the material being treated.
2B Mill Finish – This is a widely used stainless steel finish, common in industrial, chemical and food applications. It is corrosion resistance and has a typical range from 15RA (16 gauge) – to 40 RA (7 gauge) microinches.
No. 4/Dairy Finish – For processing industries, the Dairy finish is required to meet the basic 3-A standards. It uses a 180 grit and has an RA range of 18-31 microinches.
No. 4 Finish – This finish uses a 150-grit abrasive creating a polished brushed surface. The RA range is 29-40 microinches.
No. 3 Finish – The No. 3 finish uses a 120 grit abrasive. It has a semi-polished finish with an RA range of 36 – 58 microinches.
Bead Blasted surfaces have a soft satin appearance and low reflection. The process of bead blasting utilizes bead material such as glass or ceramic beads to produce a non-directional, textured surface. The finer the blasting media, the more corrosion resistance the surface performance. The RA values are typically higher than 45RA microinches, but are dependent on the blasting process and the stainless material.
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We recently designed an in-house meat attachment test to determine performance of stainless finishes used in processing equipment. In a device designed by our technicians, we tested an electropolished panel on the left, a pickle passivated panel in the center and a bead blasted panel on the right. The 70% lean beef patty with an internal temperature of 44 degrees, was placed on each of the stainless finish examples, and the mechanism was tilted to at least 90 degrees.
The video will show that the electropolished sample demonstrated the least meat attachment.
Mepaco, part of the Apache Stainless family, offers mechanical and chemical finishing in-house. Many customers specify our high-performance finishes to reduce food safety risk and to create sanitation efficiencies.
Contact our sales and application experts for more information.
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