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What is the passivation process?

Stainless Steel is protected against corrosion by a naturally forming passive layer – the Chromium Oxide layer. If this is disrupted, by cutting, welding, heating, grinding or through contact with chemicals, the stainless steel loses its protection against corrosion. The passive layer, or Chromium Oxide layer, can be restored by a process known as passivation. Passivation is achieved by contact of the stainless steel with a strong oxidizing agent (nitric acid) or a chelating agent (citric acid). Transflow Industrial Services Limited (TISL) have over a quarter of a century of experience in passivation with both nitric and citric acid in the UK and overseas on a wide variety of equipment in accordance with ASTM A380, A967 and BSEN 2516. WFI Systems, Purified Water System, Product Transfer and Manufacture and Clean Steam Systems each have unique designs which require consideration when passivating.

The passivation service presented by Transflow Industrial includes

  • Quality Control of every stage with comprehensive RAMS, COSHH assessments and support documentation
  • High quality equipment individual to each job – pumps, tanks, hoses, adaptors
  • Ferroxyl Test to confirm presence of passive layer after process
  • Off-site Baths and Immersion Tanks with clean room for drying, testing and wrapping
  • Vessel Entry/Confined Space access
  • Optional Derouging stage if required to bring existing system up to standard of new equipment
  • Trained and competent personnel experienced in cleaning a wide variety of systems
  • Paste Passivation of small blemishes in clean rooms
  • Control of Waste Chemicals and Disposal according to Environment Agency legislation with Control Documentation kept for 7 years

Our Specialized Team

TISL have worked in Healthcare, Pharmaceutical, Food Manufacture, Biotechnology and Research & Development sites and are used to working to Good Manufacturing Guidelines (GMP) practice.

TISL staff are highly trained, well motivated and competent. Examples of training regularly undertaken are; Client Contractor National Safety Group (CCNSG), Safety Passports, COSHH and Risk Assessment Awareness, Working At Height, Confined Space, Manual Handling and ADR.

View Our Wide Array Of Specialist Services


Our Passivation services allows you to restore corroded stainless still through the use of citric and nitric acid.


Degreasing of Components, Pipes, Fabrications and Systems is necessary to remove mineral oils, greases and debris adhered to product contact surfaces. This can stop the potential risk of explosion in pipes and oxygen service equipment.


When stainless steel develops iron oxide due to corrosion, it is known as rouge. This is unacceptable in many production environments and is removed by a process known as Derouging or Pickling. View our specialist Derouging service.

Biofilm Removal & Sanitisation

Our specialist team will decide on the ideal biocide for the conditions to execute this harsher treatment.

Chemical  Descaling

Chemical Descaling is necessary to remove water hardness scale or limescale from heat exchange equipment such as boilers, heat exchangers, calorifiers, tube bundles, autoclave jackets, water systems and cooling towers.

Pre-commission Flushing

It is important for the operation of water systems after commissioning that they are cleaned and treated properly at pre-commission stage. TISL are able to offer flushing in accordance with BSRIA Guidelines throughout the UK and have experience of flushing systems up to 30m3 in volume.

Ribflavin Testing

TISL are able to carry out on-site testing of sprayballs within your facility to ensure full coverage of vessel internals. With many new and re-purposed vessels having commissioning manuals missing or incomplete, evidence of the effectiveness of sprayballs at wetting surfaces is sometimes missing.

Customer Support

Contact us today with any enquiries or for a quote on a service. Our specialist team are here to help you.