Definition - What does Grain Dropping mean?
Grain dropping refers to a physical occurrence whereby small intermolecular component material of a metal dislodges from the general metal surface due to corrosion along the intergranular crystalline boundaries of a metal.
Corrosionpedia explains Grain Dropping
Grain dropping is most readily observed in cases of deterioration of metal intermolecular boundaries. This deterioration is due to the erosion of cross-sectional surface thickness due to the propagation of cracks in a metal.
Stainless steel is particularly prone to grain dropping due to intergranular corrosion. This is heightened at high temperatures ranging from 425°C to 870°C. At these temperatures, chromium carbide is formed at the grain boundary and chromium is depleted - causing the loss of hardness and corrosion resistance of the metal.
Grain dropping causes loss of entire grains and structural damage and is difficult to remediate once it has begun due to its self-propagating mechanisms.