Crevice corrosion is localized attack in narrow gaps; which components are commonly susceptible?

• A. Bolts, flanges, gaskets, and deposits
• B. Flat surfaces
• C. HVAC ducts
• D. Piping elbows

Answer: (A)

Crevice corrosion happens when a tight, narrow gap traps solution and becomes stagnant, creating a local electrochemical cell where the metal inside the crevice becomes anodic compared to the surrounding metal. This is most likely to occur at interfaces where tight joints and sealants create confined spaces, such as bolted connections with flange faces and gaskets, especially if there are deposits left in the joint. Those conditions form the perfect crevice for aggressive chemistry to develop and drive localized attack under the seal or deposit.

Flat surfaces don’t create the confined environment needed for crevice corrosion to develop as readily, HVAC ducts aren’t typically exposed to the aqueous conditions that drive this form of attack, and piping elbows, while they can corrode, don’t routinely present the persistent narrow crevices that bolts, flanges, and gaskets do.