Stainless  Restora‚Äčtion Ltd

Metal Finishing and Surface Engineering Technologies

SRL Technical Library

PICKLING AND PASSIVATION TROUBLESHOOTING  During, following or indeed before the cleaning operation all sorts of strange things can occur as a result of the chemicals used. Our technical library gives a variety of examples that SRL has encountered along its way. This list is by no means complete - these pages will be continually updated as we/you experience other strange phenomena.

Halos Shadows

Pickling Halos or Shadows


These marks appear on the surface of the steel following a pickling operation always in areas where some form of thermal heat cycle has taken place, either along weld seams or on flat surfaces where heat from welding has passed through the plate/sheets thickness. Also areas where the surface has been heated to straighten or bend / form the surface are prone to halo's or shadows.Note: they are not evident before pickling. They come about because of the thermal cycle that has altered the grain (size) structure in the microstructure of the steel.

Possible Detriment

These areas provided they have been pickled are not considered deleterious to the corrosion resistant properties of the steel.


This problem does not really have a solution since heat treatment and thermal cycles are an inevitable part of fabrication. However, SRL do have a product, XP2001, that when applied before a pickling operation will remove any evidence of a Halo. The XP2001 is particularly good on sheet stainless steel along weld seams.

Method: As explained SRL do have a product from preventing Halo or Shadowing on sheet stainless steel. The xp2001 should be rubbed along the weld seam, making sure to cover both weld and HAZ, a 2" wide band will suffice. Rub in the product, xp2001 until the weld oxide is mostly removed. Wipe the area down with clean water and then immerse in pickle bath or spray with pickle gel.

Products  Available

Pickling Products

Cleaning Products

Technical Notes

It is important to follow the instruction given for each individual product used and the advice given in the "product application data sheets" available on line in the product section of SRL Chemical and Analytical Services Ltd.

Information given in this page may be subject to alteration without notice.

Care has been taken to ensure that the contents of this publication are accurate but SRL Site Services Ltd do not accept responsibility for errors or for information that is found to be misleading.

Suggestions for, or descriptions of, the end use or application of products or methods of working are for information only and the company accept no liability in respect thereof.

Before using products supplied or manufactured by the company the customer should be satisfied of their suitability.

If further assistance is required, we have access to extensive research facilities, we will often be willing to help.

Stainless Restoration Ltd, Adamsons Industrial Estate, Hyde SK14 1EE

Stainless Restoration Ltd offer an Electropolishing service to the stainless steel fabrication/manufacturing industry at its newly refurbished fully automated Electropolishing plant at Hyde Manchester.