Stress Corrosion Cracking
Types of Corrosion found in Stainless Steel & Nickel Alloy
A material failure may be accelerated by the combined effect of corrosion and mechanical stress. Two examples of such processes are stress corrosion cracking and corrosion fatigue.
The most common type is transgranular stress corrosion cracking, SCC, which may develop in concentrated chloride-containing environments. Previously, it was generally considered that an elevated temperature was necessary for SCC to occur. In recent years, however, SCC has been experienced at ambient temperature on standard grade steels like 304L or 316L that were exposed to high tensile stresses. In these cases the steel surface was contaminated with solid salt deposits and the humidity of the atmosphere was rather high. These two factors resulted in a thin liquid film saturated with chloride. Other contaminants, such as H2S, may increase the risk of SCC in chloride-containing environments. Other environments that may give rise to SCC, particularly on low alloy steels, include very alkaline solutions at high temperatures. A typical SCC attack takes the form of thin, branched cracks.