The main difference between pitting and crevice corrosion is the geometry of the corrosion site. Whereas pitting corrosion occurs across the surface of a component, crevice corrosion is associated with a crevice, be that one that forms around a fastener, washer or joint, in a sharp corner or in an area where the flow of a liquid is slowed i.e. a dead spot.
If a corrosion pit is allowed to continue to corrode, in effect it forms its own crevice and the rate of corrosion will accelerate as the conditions within the pit become more aggressive.
Pitting corrosion is usually detectable through a thorough visual inspection, with pits able to grow deep enough to perforate a component. This type of corrosion also facilitates the initiation of cracks in tensile stressed components. Environments with higher concentrations of chloride are prone to pitting corrosion, especially at higher temperatures.
Whilst examining components for pitting corrosion, you should look for reddish-brown iron oxide deposits plus potential pits that have formed on the metal surface.
With regards to crevice corrosion, crevices exist between joints and underneath dirt and deposits that could have accumulated on surfaces.
If you have any more questions about the differences between pitting and crevice corrosion, please get in touch with Langley Alloys today. If your equipment is showing signs of corrosion, we can also advise you on the best alloys for your application.