Why are Mirror Polishing and Grinding Important in the Pharmaceutical Industry?
Stainless steel and its mirror polished or grinded surface finish are key features for food and pharmaceutical freeze-drying chambers. But why? Is it an aesthetic question that has become a habit over time or is it a matter of functional reasons?
Stainless Steel
Just as happens in the food market with industrial kitchens, even more so in the pharmaceutical industry it is necessary to work in sterile environments.
Austenitic steel, also called 18/10 stainless steel or Inox steel (from the French ‘inoxydable’) or stainless (in English) or Rostfrei (in German), guarantees sterility. In fact, stainless steel is a biologically neutral and therefore antibacterial material. Unlike other metals, stainless steel does not change color, odors or flavours of the materials it comes into contact with and does not release toxic substances that could contaminate them. For this reason, stainless steels of this type, called AISI 304 and AISI 316, are used in the pharma industry as well as in the food industry.
Roughness: What the Pharmaceutical Industry Requires
Thanks to chromium, stainless steel is equipped with a very thin protective film that prevents corrosion, self-regenerates in case of damage and makes painting optional. However, multiple finishes are used to define the surface.
These basic treatments, often followed by further adjustments, aim to adapt the natural aesthetics of stainless steel to different contexts but also to reduce its peaks and valleys. In fact, roughness and surface finish are intimately related. And it is precisely by decreasing the former that the hygienic and safety characteristics required by the pharmaceutical sector can be obtained.
Regulations in the food industry require a surface roughness of less than 0.8µm for the parts in contact with food, while it must be even lower in the pharmaceutical sector to be compliant with international standards (e.g. less than 0.5µm according to ASME Bio Processing Equipment).
Surface Finishing
Depending on the aesthetics and specifications desired, stainless steel may require different surface treatments:
- grinding
achieved by rotating brushes and possibly a manual processing, it gives a particularly elegant matt appearance to stainless steel;
- shot peening
thanks to the action of aluminum oxides, steel, ceramic or glass grains, the surface gets uniform, less subject to halos, protected from corrosion due to welding oxidation and able to contrast with top transparencies;
- mirror polishing
after using erosive belts, stainless steel is treated with cloths, abrasive pastes and polishing creams to get a mirror effect.
Stanless Steel Mirror Polishing
Stainless steel mirror polishing is especially required for products intended for the pharmaceutical and food industries, which require surfaces with a very low level of roughness.
This finish gives surface compactness without porosity. Therefore it guarantees easy cleaning, which means both high bacterial removability and low bacterial retention.
To guarantee the lack of contamination, TEC-SIM manufactures only stainless steel. We carry out mirror polishing with abrasive belts to remove all imperfections. After that, we treat stainless steel with polishing cloths and abrasive polishing paste in order to obtain a shiny, mirror-like surface. The finishing level in TEC-SIM is so high that our shelves reach a homogeneous roughness between 0.2<Ra <1.6µm, based on the specifications requested by customers.
Automated Mirror Polishing and Griding
At TEC-SIM, we have recently invested in the installation and optimization of a grinding and polishing robot. This robotic automation complements the polishing work traditionally carried out by hand. In this way, it partially overcomes its issues and limitations as well as it makes TEC-SIM climb another step forward towards continuous improvement.
