Why pickling?

Pickling ensures the corrosion resistance of stainless steel work pieces. Non-corrosive ("rust-free") steel is characterised by more than 10,5 percent chrome. Based on the fact by a high chrome portion, a protective and close passive layer of chromium oxide is formed at the material surface.

The requirements for the forming of a error-free and effective passive layer is a pure metallic surface with a sufficiently high concentration of chrome.

At heat treating processes, for example like welding, scale layers and annealing colours will be occur. Those injure the passive layer and leads to chromium poor regions. Also at mechanical processes, during storage or transporting the passive layer can be insured. Due to this the material loses his corrosion resistance.

A clear sign for the loss of the corrosion resistance is the occurrence of "rust". But also against other types of corrosion like pitting corrosion, crevice corrosion and inter-crystalline corrosion the material get more vulnerable.

Professionally pickled stainless steel surfaces are pure metallic. The surfaces are free of scale layers, annealing colours and external ferrite. Thus the material have his full corrosion resistance and a decorative metallic appearance.

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