Which of the following is NOT among the four common corrosion mechanisms?

• A. Uniform corrosion
• B. Stress corrosion cracking
• C. Pitting corrosion
• D. Crevice corrosion

Answer: (B)

The main idea is recognizing the typical categories engineers use to describe corrosion itself versus failures caused by stress. The standard four corrosion mechanisms are uniform corrosion (general, even thinning of the surface), galvanic corrosion (dissimilar metals in contact in an electrolyte, where one metal corrodes preferentially), pitting corrosion (localized holes or pits), and crevice corrosion (in confined spaces where chemistry differs from the surrounding environment). Stress corrosion cracking is a cracking failure that happens when a susceptible metal is under tensile stress in a corrosive environment. It doesn’t fit into the four basic mechanisms because it’s driven by the combination of stress and corrosion leading to crack propagation, not by uniform loss, simple galvanic action, localized pits, or crevice effects. Therefore, stress corrosion cracking is the one that’s not among the four common corrosion mechanisms. To prevent it, you’d manage stresses, choose more resistant materials, or apply protective measures such as coatings or inhibitors.