Metals Susceptible to Intergranular Corrosion

Intergranular corrosion can occur in many alloys. The most predominant susceptibilities have been observed in stainless steels and some aluminum and nickel-based alloys. Stainless steels, especially ferritic stainless steels, have been found to become sensitized, particularly after welding. Welding causes the precipitation chromium carbide phases at grain boundaries in the heat affected zone (HAZ). This in turn results in intergranular corrosion within the HAZ of the stainless steels. Aluminum alloys also suffer intergranular attack as a result of precipitates at grain boundaries that are more active. Alloys that fall into this type of corrosion include 5083, 7030, 2024, and 7075. Exfoliation corrosion is considered a type of intergranular corrosion in materials that have been mechanically worked to produce elongated grains in one direction. This form of corrosion has been experienced in certain aluminum alloys. High nickel alloys can be susceptible by precipitation of intermetallic phases at grain boundaries. The intergranular corrosion process is however more complicated in nickel-alloys than in stainless steels or aluminum alloys.