ANS:C - along grain boundaries of

Intergranular corrosion occurs along grain boundaries of stainless steel. Stainless steel contains chromium, which forms a protective oxide layer on the surface, providing resistance to corrosion. However, when stainless steel is exposed to certain conditions, such as high temperatures or improper heat treatment, chromium carbide can precipitate along the grain boundaries, depleting the chromium content in those regions. This depletion of chromium makes the grain boundaries susceptible to corrosion. As a result, intergranular corrosion occurs preferentially along the grain boundaries of stainless steel, leading to localized corrosion attack in these areas. This type of corrosion can compromise the integrity of the material, particularly in applications where corrosion resistance is critical. It's important to note that intergranular corrosion typically occurs in stainless steel alloys with carbon contents above a certain threshold (often referred to as sensitized stainless steel), and it is less common in low-carbon stainless steels or highly alloyed stainless steel grades.