What is stress corrosion cracking and which conditions promote it?

• A. Cracking due to tensile stress in a corrosive environment; promoted by chlorides, high tensile stress, and susceptible alloys.
• B. Cracking caused by random mechanical impacts.
• C. Cracking only occurs in non-corrosive environments.
• D. Cracking is caused by electrical overload.

Answer: (A)

Stress corrosion cracking occurs when a material under tensile stress is exposed to a corrosive environment, and the combination of stress and chemical attack drives crack initiation and growth. The environment must be aggressive enough—chloride-containing solutions are a classic example—so the corrosion process and the stress work together to open and propagate cracks, often along grain boundaries. The alloy’s susceptibility matters too; some materials are much more prone to SCC than others, so high tensile stress, a corrosive environment, and a susceptible alloy together create the highest risk. The other scenarios don’t fit because random mechanical impacts don’t involve a corrosive driver, non-corrosive environments can’t promote SCC, and electrical overload is a different failure mechanism not defined by the stress-corrosion interaction.