What are examples of internal stress corrosion?

• A. Surface rust due to humidity
• B. Intergranular attack due to grain boundary segregation
• C. Stress induced by press-and-shrink fits and those in rivets and bolts
• D. Pitting due to acid exposure

Answer: (C)

Internal stress corrosion happens when the metal already has tensile stresses inside it, and a corrosive environment enables that stress to drive cracking or accelerated corrosion. The clearest example is the residual or applied tensile stresses created by assembly processes—such as interference (press) fits and shrink fits, and the stresses found in rivets and bolts. These internal stresses act with the environment to initiate and propagate cracks even if the surface isn’t severely attacked by the environment alone.

Surface rust due to humidity is general environmental corrosion at the surface, not driven by internal stresses. Intergranular attack from grain boundary segregation is a microstructural corrosion mechanism tied to sensitization, not to internal stresses. Pitting from acid exposure is localized attack due to chemistry, not specifically caused by internal stresses inside the metal.