Corrosion resistance of austenitic steels.
Wet Corrosion
These steels are mainly used in wet environments. With increasing chromium and molybdenum contents, the steels become increasingly resistant to aggressive solutions.
Austenitic steels are more or less resistant to general corrosion, crevice corrosion and pitting, depending on the quantity of alloying elements. Resistance to pitting and crevice corrosion is very important if the steel is to be used in chloride-containing environments.
Resistance to pitting and crevice corrosion increases with increasing contents of chromium, molybdenum and nitrogen.
The most common austenitic Cr-Ni and Cr-Ni-Mo types are sensitive to stress corrosion cracking. Higher alloyed austenitic grades like 254 SMO®, ferritic grades or duplex grades are better alternatives in applications where there is risk of stress corrosion cracking.
The rich chloride content of seawater makes it a particularly harsh environment, which can attack stainless steel by causing pitting and crevice corrosion. However, two stainless steel grades designed to cope with this environment have been developed by Outokumpu - 254 SMO® and 654 SMO®.
254 SMO® has a long record of successful installations for seawater handling within offshore, desalination, and coastal located process industries.
Some crevice corrosion has still been reported and for more severe situations, i.e. severe crevice geometries and elevated temperatures, the natural selection should be 654 SMO®.
High Temperature Corrosion
See High Temperature Grades