Definition - What does Stress Corrosion mean?
Stress corrosion, also known as stress corrosion cracking, is a type of corrosion that occurs due to the simultaneous action of a corrodent and a sustained tensile stress. This mechanism is characterized by corrosion in the microscopic granular composition of a metal's surface. The introduction of stresses (either applied or residual) causes the boundaries to open, introducing fine cracks on the metal's surface.
Corrosionpedia explains Stress Corrosion
The interface where the grains of a metal contact each other is known as the grain boundary. When metals are melted, either due to the manufacturing process or during welding, impurities tend to accumulate and segregate the grain boundaries. This segregation and increased impurity concentration make passivation of these areas less effective, thus making these areas less corrosion resistant than the rest of the surface.
Due to minimized passivation, corrosion occurs at these vulnerable areas, creating points of weaknesses. Applied or induced stresses then cause cracks to open up at these locations, while the rest of the metal's surface remains relatively unaffected.
Stress corrosion is typically classified as a severe type of corrosion because brittle failure can occur with little to no warning. This condition can be avoided by controlling hardness and stress levels, introducing compressive stresses (e.g., shot peening) and using protective coatings to prevent corrosion of the grain boundaries.