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.

Roughing

Identification

Its appearance can take on many colours from grey or brown to red (hence the name rouging). Can be across a whole surface or in isolated patches. It can occur within days, week, months or even many years after the system has been in service.
There are no reported cases of rouging in Duplex steels, tends to be confined to 300 series stainless steel. The other strange phenomena is that it is peculiar to high purity water systems and steam systems. 

The surface will appear as if it has been subjected to a high temperature thermal cycle and exhibit all the signs of such as rainbow coloured oxidation bands, however, the colour will not break the surface and yield no deposit if attempted to be wiped off with a cloth. If you wish to understand more about the cause and mechanism of rouging visit our technical library section and download the technical data sheets on this subject.

Possible Detriment

The surface will look stained.

There are different degrees of severity of rouging, some times it will break the surface and manifest itself as flake/dust deposit, in other cases it will only appear as a stain and give the impression it is trapped under the surface as if under glass.

Solution

 The problem is only superficial and does not run the thickness of the steel. It is only a few um thick and can be removed either by a mechanical polishing method, however care has to be made not to render the surface prone to further corrosion attack by introducing scratches/crevices/roughness to the area.

The most common way of dealing with this phenomena is to conduct a pickling operation on the surface.

Note: there is no guarantee that this phenomena will not reappear.

Method: Since this phenomena only occurs whilst in service the pipe work or vessel will have to be pickled using either a circulation method or a manual spray gel method. 

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.