Electropolishing & Mechanical Polishing Services

Astro Pak offers a full selection of cleaning and surface polishing services tailored to the individual need of each client. Individually, mechanical polishing, electropolishing, and electrolytic cleaning can be standalone processes. However, combining one or more of these services together will optimally address certain requirements. When used with our chemical cleaning and passivation services, customers will experience the ultimate in corrosion and contamination protection for extended, reliable performance.

Astro Pak uses custom-designed tooling to ensure optimal contact with intricate stainless-steel surfaces, along with proprietary chemistry, for superior results. The surface roughness reduces to a level at or below the originally specified surface finish.  “Ra,” or surface roughness, is confirmed using microscopic and profilometry testing to ensure absolute quality assurance. Our Profilometers gauge surface roughness while Ultrasonic testers measure tank wall thickness. Recording these measurements before and after remediation allows our highly trained technicians to produce results that meet or exceed industry standards.

Astro Pak performs all three services on-site to help customers maintain or improve upon the surface finish conditions of vessel interiors or exteriors with minimal downtime. When used as part of the pre-commissioning of a vessel, our services increase system reliability by overcoming manufacturing and installation-generated issues. Our specially trained confined space entry crews are highly skilled in servicing equipment that are difficult to access. They can work 24/7 to quickly return process vessels, large or small, back into service. In addition, we also offer these services in our nationwide network of shops.


What is Mechanical Polishing?

Mechanical Polishing is a surface finishing process whereby abrasives are used to smooth and/or polish a surface. This results in uniform surface conditioning to meet or exceed ASME BPE and ASTM B912 standards. Mechanical polishing removes corrosion, pitting, scratches or etchings which compromise the passive layer of stainless steel, creating a low-chromium area that is more susceptible to corrosion. This damage can be caused by mechanical actions or chemical reactions. Mechanical Polishing also smooths welds where ferrules and valves have been replaced or added. Mechanical polishing alone is often sufficient for dry product vessels. For other applications, it is most often the first step prior to electropolishing and passivation.

Astro Pak Mechanical Polish vs. Electropolish



What is Electropolishing?

Electropolishing is an electrochemical surface finishing process using a DC current delivered through an electrolyte solution to dissolve the surface of metal to a limited depth. The end result is a finish that meets or exceeds biopharmaceutical surface finish requirements. It can reduce Ra measurements by up to half that from mechanical polishing alone.

Additionally, electropolishing removes impurities, inclusions, and other embedded contaminants, also known as the Bielby layer, which forms during mechanical polishing.  The result is a smooth, mirror-like finish where residue, contaminants and even single-cell bacteria, will have no place to lodge. Often, electropolishing is the final process in preparing a vessel for service. However, combining electropolishing with passivation achieves a smooth chromium rich surface with improved cleanability and superior resistance to corrosion. This level of finish is critical for high purity applications.

Benefits of Electropolishing

  • Improve Cleanability
  • Enhance Durability
  • Improve Sterility
  • Increase Corrosion Resistance

Astro Pak before and after Mechanical Polishing and Electropolishing


Microscopic View of Electropolishing


Electrolytic Cleaning

Electrolytic cleaning is a short-form version of Electropolishing using similar tooling and chemistries. It is used to remove several types of rouge, product residues, and heat discoloration from welding. It also has the advantage of speed over traditional derouging and other chemical cleaning processes.

System & Equipment Experience

  • Process vessels and reactors from 2 liter to 30,000 gallon+
  • Fermenters
  • WFI, Buffer and Media prep and hold vessels
  • Autoclaves
  • Laboratory fixtures and equipment
  • Vessels, V-blenders and Powder Blenders
  • Stainless Tubing
  • All types of components such as Filling & Conveyor hardware
  • Pumps, spray balls, dip tubes, agitators and a host of other peripheral equipment
  • Heat exchangers
  • OEM and repairs
  •  Accela-Cota tablet coating machines
  • Fluid bed dryers


  • ASME BPE (BioProcessing Equipment Standard)
  • ASTM B912 Passivation of Stainless steel using Electropolishing
  • EFS 1 – 4 (Electropolish Finish Standards 1- 4)
  • ISO 15730
  • SEMI F19-0304 Specification for the Finish of the Wetted Surfaces of Electropolished 316L Stainless Steel Components
  • AMAT 0250-13605

Markets Served

  • Biopharmaceutical
  • Aerospace, Military & Defense
  • Healthcare
  • Water & Wastewater Distribution
  • Semiconductor
  • Powder & Tablet Manufacturing
  • Marine
  • Nuclear
  • Petrochemical


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