The metal and alloys are made up of grain, in micro level the structure is separated by grain boundary. Intergranular corrosion is preferential attacks on the grain boundary where grain remain largely unaffected. This type corrosion occurred due to segregation of impurity (precipitation of nitrides, carbides, and other intermetallic phases, such as sigma phase) on the grain boundary. Such precipitation can produce zones of reduced corrosion resistance in the immediate vicinity.

This mainly occurs with incorrect heat treatment service, materials are liable to crack or fail by intergranular corrosion (IGC) much more rapidly than properly treated materials. In any case the mechanical properties of the structure will be seriously affected. Dashinspectorate can carry out testing as per ASTM A262, ASTM A923, ISO 3651 and ASTMG28 standards.

During services if the material exhibits localized pits or gaps on its surface, pitting or crevice corrosion may be the culprit. Pitting corrosion is characterized localizes pit holes, and crevice corrosion occurs where two materials meet. Material resistance to pitting and crevice should be assessed before its usage. Dashinspectorate provide pitting and corrosion test based on ASTM G48 .