Chrome-Carbide Precipitation

A chemical reaction sometimes occurring at welding of austenitic stainless steels, containing more than 0.05% C. At the high temperature, a chromium-iron carbide is formed. Chromium, near the boundaries of the grains, flows to the boundaries and unites with carbon, thus depleting the chromium supply in the metal near the grain boundaries. The alloy loses its corrosion resistance as the grain boundaries are attacked in acid water solutions. The attack is called intergranular corrosion, which in turn can cause severe damage from mild agents that are not at all expected to attack stainless steels.