Corrosion handbook
06/21 11
Fig. 11: Scanning electron micrograph
image of a selective attack Welded
zone of a 1.4401, (A4, 316) material.
0RUHQREOH /HVVQREOH
1.2.5 Intercrystalline (intergranular) corrosion
Intercrystalline corrosion is a special form of localized corrosion, where the
corrosive attack takes place in a relatively narrow path, preferentially along the
grain boundaries in the metal structure. The most common effect of this form of
corrosion is a rapid mechanical disintegration of the material (loss of ductility).
Usually it can be prevented by using the right material and production process.
A well-known example relevant to the construction industry is the sensitization of
stainless steel. When certain grades of this material are kept within a temperature
range of 500 °C to 800 °C for a considerable time, such as during a welding
process, chromium-rich carbides are formed, resulting in chromium depletion at
the grain boundaries. Consequently, the grain boundaries possess a lower degree
of corrosion resistance than the residual material, leading to localized corrosive
attack (see Fig. 11).