When steel is heated by welding or other means to the extent that a heat tint or oxide scale layer is visible, the layer below that has been depleted of chromium, thereby making the steel less resistant to corrosion. Pickling steel is the process of applying an acid solution to remove heat affected zones along with the underlying chromium reduced layer from the stainless steel. Pickled steel is free from surface carbon steel contamination and embedded iron particles. It typically leaves a dull, matte gray finish. Simply stated, pickling removes the heat affected layer of stainless steel and prepares the surface for passivation.