Acid Cleaning and Passivation (Pickling)

Acid Cleaning

The Acid CLeaning is the removal of any high-temperature scale and any adjacent low chromium layer of metal from the surface of stainless steel by chemical means. Where the steel has been heated by welding, heat treatments, or other means, to the point where a colored oxide layer can be seen, there is a chromium depleted layer on the surface of the steel underneath the oxide layer. The lower chromium content gives lower corrosion resistance. To restore the best corrosion-resistant performance, the damaged metal layer must be removed, exposing a fully alloyed stainless steel surface. Mechanical removal may leave abrasive or other particles embedded (interfering with corrosion performance) or may be impractical, so chemical means are usually employed. Pickling involves metal removal and a change or dulling in the visual brightness of the metal.

Passivation 

The passivation of corrosion resistant steels is used for strength the natural layer of passivation of the steel (superficial oxide layer) with the aim of improving its resistance to corrosion. Depending on the type of passivation, the process gives to substrates a better behaviour towards different factors of environmental corrosion. Also, it cleans the surface of free iron particles and offers to steel a better resistance to fatigue.

There are two types of passivation:

  • Type I: superficial pickling with fluorimetric acid and passivation with nitric acid.
  • Type II: superficial pickling with hydrochloric acid and inhibiting agent and passivation with nitric acid and dichromate.

Acid Cleaning and Passivation (Pickling)

Both acid cleaning and passivation are chemical processes that are utilized to provide protection to metals against corrosion and pitting.  In either process, an acidic solution is applied to the metal surface to remove contaminants and to aid in the formation of a continuous, chromium-oxide passive film.  Without pickling and/or passivation, stainless steel is subject to corrosion in service which can lead to costly quality issues.

Listed below are just some of the types of equipment that have been thoroughly performed by pickling and passivation in services industries

  • Heat Exchange & Pressure Vessels
  • Oil Refinery Pipelines Plants
  • Chemicals Machinery Plant
  • Pharma, Dairy & Food Process Plant
  • Electrical Panel Board Plant
  • Stainless Steel User

Acid cleaning (Pickling) and Passivation Solution is very effective & easy to use for cleaning of large equipment like S.S. vessels, tank, agitator, dairy machinery, fermentator, internals as well as externals of pipes.

  1. Removes built-in corrosion
  2. Removes scales, discoloration, burn spots, ferritic and austenite contamination
  3. Prevents corrosion & restores full corrosion resistance.
  4. .Removes metallic contaminants, oxide scales, rust spots & annealing colors.
  5. Retains mill finish.
  6. Gives a uniform, smooth, contamination, and sterile particle-free, passive surface.

Vessel and Piping Pickling

Acid Cleaning (Pickling)      
Pickling is the removal of any high-temperature scale and any adjacent low chromium layer of metal from the surface of stainless steel by chemical means. Where the steel has been heated by welding, heat treatments, or other means, to the point where a colored oxide layer can be seen, there is a chromium depleted layer on the surface of the steel underneath the oxide layer. Pickling involves metal removal and a change or dulling in the visual brightness of the metal.

System Passivation

System Passivation

For all types of heat exchange equipment, pipework and vessels, it can help to:

  • Provide internal surface protection against corrosion
  • Protect and extend asset life