My products must be highly polished; what’s best for me?

The best solution to meet your requirements consists in electropolishing the product, a technique which uses an electrochemical process to remove a surface film of between 10 and 40 microns, thereby obtaining a smooth and polished product.

I want to remove the oxide after welding; what can be done and what are the alternatives?

The treatment you need to carry out is acid pickling or anodic-picking, a chemical or electrolytic treatment which removes the superficial oxide layer. In the case of anodic-pickling it will also be simultaneously passivated.

What is meant by pickling, electropolishing and passivation? What appearance will the 3 different treatments give to my products?

Pickling is a chemical treatment which removes a thin surface layer, <4 micrometres, and which allows the removal of rust, oxide and other external contaminants; the appearance of the product will be that of stainless steel before formation of oxide with a light grey colour. Electropolishing is a technique which uses an electrochemical process to remove a surface layer of between 10 and 40 microns, thereby obtaining a smooth and polished product. Passivation, on the other hand, is a treatment which facilitates the creation of the natural layer of transparent oxide which characterises stainless steel; there is little change to the appearance of the steel in this case.

Is it always necessary to carry out passivation after pickling?

After removing the oxides the stainless steel parts are able, over time, to restore the protective chromium oxide film.

The “self-passivation” process requires lengthy times and particular exposure conditions: the parts must be left exposed in well oxygenated environments and they must not come into contact with contaminating agents which can give rise to corrosion.

“Passivation” is a process which allows the formation of this protective layer to be accelerated with the aid of suitable products and is not a substitute for pickling.

Is it worth passivating a part without first pickling it in order to increase the corrosion resistance?

If a stainless steel part does not have any oxidation, a single passivation treatment can decontaminate the surface and increase its resistance to corrosion. A typical case is that of machined parts.

Why does stainless steel still rust?

Stainless steel has elements (chrome, nickel) in its alloy which oxidise naturally when in contact with oxygen, forming a transparent, colourless and invisible film which protects it.

If a contaminant is present, such as contact with iron, this will oxidise preferentially, creating brown marks (normally called rust)

I want the treatments to be carried out without having to worry about anything, what’s the best solution for me?

The solution which meets your needs can be found in our treatment centres, where, thanks to our 70 years of experience, your products will be in excellent hands: we will take the utmost care to give you a perfect result. We operate 24 hours a day, allowing you to remotely monitor the progress of the work.

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