What conditions promote stress corrosion cracking (SCC)?

• A. Sustained tensile stress and a corrosive environment
• B. Low temperatures and no stress
• C. Static, unstressed metals in dry air
• D. Use of only non-metallic materials in service

Answer: (A)

Stress corrosion cracking occurs only when two factors line up: a susceptible metal under a sustained tensile stress, and a corrosive environment. The mechanical pull from the stress provides a driving force for crack initiation and propagation, while the environment chemically or electrochemically weakens the metal at flaws or grain boundaries. Together, they enable cracks to grow over time even at stresses lower than the metal’s normal yield strength, which is why a corrosive medium alone or a static, unstressed piece in dry conditions won’t cause SCC. Non-metallic materials aren’t susceptible to SCC in the same way metals are, so using only non-metals in service wouldn’t produce SCC.