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In general, crevice corrosion is of greatest concern for materials which are normally passive metals, like stainless steel or aluminum. Crevice corrosion tends to be of greatest significance to components built of highly corrosion-resistant superalloys and operating with the purest-available water chemistry.
Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy containing a minimum level of chromium that is resistant to rusting and corrosion. Stainless steel's resistance to corrosion results from the 10.5% or more chromium content, which forms a passive film that can protect the material ...
The photos show the typical microstructure of a normalized (unsensitized) type 304 stainless steel and a heavily sensitized steel. The samples have been polished and etched before taking the photos , and the sensitized areas show as wide, dark lines where the etching fluid has caused corrosion.
This limits the usefulness of austenitic stainless steel for containing water with higher than a few parts per million content of chlorides at temperatures above 50 °C (122 °F); mild steel cracks in the presence of alkali (e.g. boiler cracking and caustic stress corrosion cracking) and nitrates;
SAE 316 stainless steel is a molybdenum-alloyed steel and the second most common austenitic stainless steel (after grade 304). It is the preferred steel for use in marine environments because of its greater resistance to pitting corrosion than most other grades of steel without molybdenum. [1]
The unshaded bars indicate the location on the chart of those steels when in acidic/stagnant water ( like in the bilge ), where crevice-corrosion happens. Notice how the *same* steel has much different galvanic-series location, depending on the electrolyte it's in, making prevention of corrosion .. more difficult.
Thus, this type of corrosion typically occurs in alloys that are protected by a tenacious (passivating) oxide film such as stainless steels, nickel alloys, aluminum alloys in environments that contain an aggressive species such as chlorides (Cl –) or thiosulfates (S 2 O 3 2–). In contrast, alloy/environment combinations where the passive ...
Corrosion in the crevice between the tube and tube sheet (both made of type 316 stainless steel) of a heat exchanger in a seawater desalination plant. Crevice corrosion is a localized form of corrosion occurring in confined spaces (crevices), to which the access of the working fluid from the environment is limited.