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GATE 2019 MT – Question 25

Physical Metallurgy · Corrosion · 1 mark · Multiple choice

Which carbide is primarily responsible for intergranular corrosion in austenitic stainless steel?

  1. Cr₂₃C₆
  2. Fe₃C
  3. SiC
  4. Mn₃C

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Show answer and explanation

Correct answer: (A) Cr₂₃C₆

Explanation

Chromium-rich Cr₂₃C₆ can precipitate at grain boundaries during sensitization. It removes chromium from neighbouring regions, weakening their protective passive film and promoting intergranular attack. Therefore A. The key mechanism is local chromium depletion rather than merely the presence of any carbide.

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