Crevice Corrosion in Stainless Steel

Under certain specific conditions, particularly involving chlorides (such as sodium chloride in sea water) and exacerbated by elevated temperatures, small pits can form in the surface of the steel.

Dependent upon both the environment and the steel itself these small pits may continue to grow, and if they do can lead to perforation, while the majority of the steel surface may still be totally unaffected.

Crevice Corrosion in Stainless Steel can be thought of as a special case of pitting corrosion, but one where the initial "pit" is provided by an external feature; examples of these features are sharp re-entrant corners, overlapping metal surfaces, non-metallic gaskets or incomplete weld penetration.

To function as a corrosion site a crevice has to be of sufficient width to permit entry of the corrodent, but sufficiently narrow to ensure that the corrodent remains stagnant.

Accordingly crevice corrosion in Stainless Steel usually occurs in gaps a few micrometres wide, and is not found in grooves or slots in which circulation of the corrodent is possible.