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What Is Pickling & Passivation

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What Is Pickling & Passivation

Pickling and passivation are two forms of chemical metal finishing that provide protective properties to metal especially against rust. Or in other terms, pickling and passivation are the name of the two processes where the metal is submerged in a bathing liquid that removes imperfections and rust from the surface of metal.

What Is The Difference Between Pickling & Passivation

On the surface there does not seem to be a big difference between the two processes. The differences come down to the intensity of the treatments.

  • Pickling uses acids that take off the surface of the metal to treat impurities as a sublevel basis.
  • Pickling leaves a greater change to the metal.
  • Passivation uses either nitric acid or citric acid that are not recognized as being as aggressive as the acids used in pickling.
  • Passivation does not typically go below the surface of the metal and does not change the properties of the metal. The oxide layer left by passivation is only .0000001 inch thick. To put that in perspective it is 1/100,000 as thick as a human hair.

What Are The Advantages Of Pickling & Passivation

Both types of metal finishing have great advantages for metal products.

  • Removes impurities that are left from the metal being manufactured
  • Protects the metal from pollutants getting into the metal and causing rusting and damage in the future
  • Leaves the surface of the metal smooth and with no imperfections
  • Increases the durability of the metals

CELCO Has Expertise In Both Pickling And Passivation

As previously mentioned, while there are great similarities in both of the processes there are also key differences. CELCO has trained experts who can assist you in deciding which choice is the best for your metal finishing needs. Please contact CELCO today!

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3 Comments

Wim RaesApril 17, 2017 at 3:26 amReply

Is passivation or pickling effective for long time protection of ss against 35% CaCl2 aqueous solution at 130 degr. C and pressure of 1.5 bara (abs.)?
Thanks.
Wim

SDJune 19, 2018 at 11:58 amReply

is it necessary or compulsory to do passivation after pickling process

Hammad Haider GhummanSeptember 24, 2018 at 11:18 amReply

Hi there, This is Hammad from Saudi Arabia, We are welding DSS ( A790 uns s32205) at our fabrication shop. We have a query whether it is mandatory to do passivation after Pickling of our welded joints as we have some of the joints which have got rusted within a week or so due to atmospheric effect.

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