Stainless  Restora​tion 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.

Stress Corrosion Cracking

Identification

Stress Corrosion

Surface cracks / fissures. The cracks are often running in the same direction and multiple.

Possible Detriment

Apart from the fact that the surface will look unsightly and indeed, if a food/pharmaceutical bearing surface it will look unhygienic.

It is quite plain that once a crack(s) appear in the surface of the steel then the mechanical properties of that surface are effected. From a corrosion point of view this too is bad news since it is corrosion, combined with stress in the microstructure that has caused this problem in the first instance. The crack (now a crevice/void) will give rise to further corrosion. Don't be surprised if you see corrosion product ie "rust" or iron oxide "bleeding" from the cracks. If the product or medium passing over the area is aggressive enough then further corrosion will occur at the corrosion site and lead to greater problem, even mechanical failure.

Solution

Very difficult to treat, if not impossible. Remember that stress corrosion cracking occurs as a result of three factors, stress, chlorides, temperature and a susceptible microstructure such as 300 series Austenitic grades of stainless steel.

The only logical suggestion would be to remove one or more of the contributing factors listed above. However, this is not always possible since Stress is often unavoidable since it is and acceptable part of fabrication / welding and often unavoidable. Chlorides and Temperature are often unavoidable in some manufacturing (service) conditions.

The only thing to do is design the stress corrosion cracking out by selecting a grade of stainless steel or other metal grade that is not susceptible to stress corrosion cracking such as Duplex or even some of the 400 series family...you will of course have to balance this consideration against mechanical properties and of course costs etc.

Note: A general clean of the surface may be possible to help remove corrosion product "rust" and minimise the contamination. Pickling is not recommended due to possible entrapment of the aggressive pickling acid in the cracks/crevices.

Method: If the rust is light then a simple cleaning operation with one of the cleaner listed in the products section will suffice.

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.