What type of corrosion occurs at grain boundaries?

Intergranular corrosion occurs at grain boundaries, which are the interfaces between individual grains or crystals in a metallic material. This type of corrosion is often a result of certain metallurgical conditions within the metal, such as the presence of impurities or phases that preferentially corrode, leading to the weakening of the structure at these critical junctions. The process can significantly reduce the overall strength of the material, making it particularly hazardous in applications where structural integrity is vital.

In metals, this form of corrosion can occur more readily in certain alloys and is exacerbated by factors like heat treatment, which can change the microstructure and stress the grain boundaries. By targeting the grain boundaries rather than the entire surface of the metal, intergranular corrosion can develop without leaving visible signs on the surface, making it insidious and potentially dangerous.

Other types of corrosion, such as galvanic, pitting, and uniform corrosion, involve different mechanisms or locations of attack on the material, thus not specifically targeting the grain boundaries in the same way intergranular corrosion does. Understanding the nature of intergranular corrosion is crucial for selecting materials and treatments that minimize such degradation in critical applications, especially in marine environments where various corrosion types can occur.