What causes the layer of chromium to be removed during heat treatment?
During heat treatment or welding, stainless steel experiences a temperature range of 550oC~850oC. Chromium and carbon react to precipitate chromium carbides along the grain boundaries. This process leads to the depletion of chromium in the adjacent narrow region along the grain boundaries. The chromium depleted region has poor resistance to corrosion compared with the normal grains where chromium content is not affected. A stainless steel is said to be sensitized when chromium carbides form in its structure. A sensitized steel is susceptible to intergranular corrosion or weld decay.
