Intergranular and Selective Corrosion

Abstract

Metals consist of micrometric size crystalline grains . The border between these grains, called grain boundary, is a peculiar and delicate region, due to a distorted crystallographic structure and possible segregation of impurities and second phases. These characteristics of non-equilibrium make grain boundaries particularly reactive, and weaker in terms of corrosion resistance , so that in some cases a localized corrosion , called intergranular corrosion , can occur. This corrosion -type attack is very severe because it leads to grain detachment, then to a reduced mechanical resistance, despite the negligible metal consumption; in some environments and in the presence of tensile stresses it triggers stress corrosion cracking. In this chapter the most common intergranular corrosion forms are described, including stainless steel sensitization , knife-line attack , exfoliation of aluminium, and selective corrosion of brass and cast iron.

The most part of piping was stainless steel , and you know that stainless steel is a great material but does not allow, I mean does not yield if cold but if warmed up it’s not so much anymore stainless.

Primo Levi, The Wrench