Which type of corrosion is difficult to detect because it happens inside the metal?

Intergranular corrosion is a type of corrosion that occurs at the grain boundaries of metals, leading to the degradation of the material from within. This form of corrosion is particularly insidious because it is not easily visible on the surface of the metal, and it can progress undetected until significant damage has occurred.

The granules in crystalline metals are composed of different phases, and when conditions such as exposure to specific chemicals or environments are present, the grain boundaries can become susceptible to corrosion. This internal corrosion is often exacerbated by factors such as stress, heat treatment, or improper alloy composition, making it crucial for maintenance personnel to use non-destructive testing methods to detect it.

Recognizing intergranular corrosion is essential, especially in aerospace applications, because it can lead to reduced structural integrity without any obvious signs on the exterior, potentially resulting in catastrophic failures if not identified and addressed in a timely manner. This is why understanding and being able to detect such hidden corrosion forms is critical in aerospace maintenance and repair procedures.