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What Is Meant By Pickling and Passivation Of Stainless Steel?

Let’s keep it simple!

A lot of people think passivation is pickling, it’s like putting the cart before the horse.

They are two distinctly different processes. Pickling removes the oxide layer and Passivation restores the oxide layer.


Pickling is a process where a stainless steel object is subjected to some form of acid treatment. The common type acids are usually a mixture of Hydrofluoric and Nitric acid.

This removes the very thin passive or chromium oxide layer which may have been affected by heat from thermal cutting and welding or other mechanical processes such as rolling, bending, guillotining and punching leaving a fully alloyed surface.

* These acids are extremely dangerous if not used correctly and by trained personnel.


Passivation is the restoration by chemical means of the thin passive layer or chromium enriched oxide layer. This layer gives stainless steels its corrosion resistance.

APPS often  sees specifications and documents asking for materials to be passivated but they have not asked for the material to be pickled.  This is where people get confused and often get the wrong products or result.

Passivation products are usually Citric or Nitric acid based, there are other formulas that are non-acid based available in the market place.

Some of AUPP Service Pty Ltd clients include:

AUPP Service Pty Ltd has worked on many a large projects around Australia:


  • SGM Fabrication and Construction ,Newcastle ANZAC Memorial Walkway 316L 74 tonnes of material 2015

  • Origin Energy, 304L pipe work for Eraring Power Station NSW

  • RCR Energy NSW, large vessels in 304L and 316L ranging from 12 to 35 tonnes which have gone to places such as Murrumba and Mt Isa in Qld.

  • Industrial Installation and Maintenance Qld, 600NB pipe spools in 2507 Super Duplex for BP Australia Brisbane refinery.

  • Transfield Worley Power Services NSW, 904L Austenitic ash hopper panels.

  • Thomas and Coffey NSW- 15 metre 600NB Sch40 316L pipe spools.

  • Delta Electricity - Austenitic 904L and Duplex 2205 ash hopper for a NSW Power Station.

  • GE Power and Water Technologies-Super Duplex 2507 -12 vessels and brine concentrators for a very large CSG project in Qld.

  • Super Duplex 2507 and Duplex 2205 pipe spools for a large desalination plant.

  • Laing O'Rourke Australia -Super Duplex 2507 and Duplex 2205 pipe spools onsite.
  • Sandvik Mining and Construction Qld- nearly 40 tonnes of 316L conveyor frames for a major coal port expansion in North Queensland.

  • Clarke Energy SA - 304L components for a major CSG plant in Qld.

  • Integro Foods-Brisbane Duplex 2205 brine lines onsite.

  • Valmec WA 2014 - APA Warumbilla Gas Plant  316L 3" oil lines onsite.

  • Clyde Babcock Hitachi 2014 shutdown in a NSW power station -2205 Duplex ash hopper panel.

  • Century Engineering SA 2014 - 2 x Duplex 2205 heat exchangers.

Would you like to get pickled and passivated?

Contact Richard Raper from Australian Pickling and Passivation Service on 0400 816 290 to discuss your next chemical cleaning, pickling, passivation and electro polishing requirements.