Heat treatment or welding forms an oxide layer on the surface of stainless and acid-resistant steels, as well as a zone underneath that is low in chromium. Removing these zones and forming a passive film is extremely important for ensuring the product’s corrosion resistance and appearance.
The best corrosion resistance is achieved through chemical post-processing, known as pickling.
The most common method for pickling individual parts, as well as strip, tube, and sheet products, is mixed-acid pickling with a combination of nitric acid (HNO₃) and hydrofluoric acid (HF). The purpose is to remove the last remnants of the oxide layer, dissolve the chromium-depleted zone, and create a passive surface.
Kröger’s pickling facilities enable both tank pickling and spray pickling for stainless and acid-resistant steels.
