Question

Which of the following is/are the causes of intergranular corrosion?

(a) Impurities at the grain boundaries

(b) Enrichment of one of the alloying elements at the grain boundary

(c) Depletion of one of the alloying elements at the grain boundary

(d) Impurities at the grain boundaries, enrichment, and depletion of one of the alloying elements at the grain boundary

The question was asked during a job interview.

I need to ask this question from Eight Forms in portion Eight Forms of Corrosion of Corrosion Engineering

Answer 1

The correct answer is:

(d) Impurities at the grain boundaries, enrichment, and depletion of one of the alloying elements at the grain boundary

Explanation:

Intergranular corrosion occurs at the grain boundaries of a metal, which is the region between individual crystals (grains) in a material. Several factors contribute to this type of corrosion:

1. Impurities at the grain boundaries: Impurities can accumulate at the grain boundaries, making them more susceptible to corrosion compared to the grain interiors.

2. Enrichment of one of the alloying elements at the grain boundary: In some alloys, certain alloying elements may become concentrated at the grain boundaries. This can create localized areas with different electrochemical properties, making these regions more prone to corrosion.

3. Depletion of one of the alloying elements at the grain boundary: In other cases, the grain boundaries may become depleted of critical alloying elements (e.g., chromium in stainless steel), which compromises the protective oxide layer and makes these areas more vulnerable to corrosion.

Thus, all three factors (impurities, enrichment, and depletion) can cause intergranular corrosion, making option (d) the correct answer.