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.

HCL Induced Pitting

HCL Induced Pitting

Identification

I‚Äčn severe cases it will appear as a mass of rust (corrosion deposit) in less severe cases it will appear as small brown spots (pits).

Possible Detriment

The surface will look stained. 

This type of pitting is sever since chlorides will attack the surface in an aggressive manner within hours of contact. The example shown was of a stainless steel surface that had been washed down by hand with a cleaner that contained Hydrochloric acid (HCL).

In the case of sheet stainless steel once pitting has started it will have broken through the "mill surface finish". This surface finish will be smooth a have a reflective property, however, once the pitting has started the "skin" is broken and the surface is scared (rather like acne scares on peoples faces) these can not be repaired or restored and will serve as weak points in the stainless steel surface. The scares appear as white / grey areas across the offending areas.

Solution

The best way to remove this kind of staining is to use an semi-pickle product Enerjex 410 solution to wipe of the corrosion product that is only iron oxide "rust". Other solutions must be used after this stage to ensure thorough cleaning. 

Care has to be made not to leave any traces of semi-pickle solution on the surface afterwards or you will be back to square one.

Method: Do only small areas, say one meter square at a time.

1. Wipe surface with Enerjex 410 using a clean cloth.
2. Wipe surface down with clean water.
3. Wipe surface down with Enerjex 410 again
4. Wipe surface down with clean water.
5. Wipe surface down with Enerjex 610 Passivator.
6. Wipe surface down with clean water.

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.