Studies on the stress corrosion cracking behavior of some alloys used in desalination plants

This paper describes a study of stress corrosion cracking (SCC) behavior of alloys resulting from the synergistic action of corrodents such as chlorid es, oxidants and H2S. Tn the this study the threshold stresses for SCC have been determined for a few generic alloys, namely mild steel, 316L, 317L, 4 30 and Monel 400, used in desalination plants. The standard Proof Rings and U-Bend samples in NACE and SHELL solutions containing H2S were used for th is purpose. Electrochemical polarization measurements were performed on the se alloys in the specified environments to study the effect of electrochemi cal potential on intergranular SCC. Structural analyses were conducted by s canning electron microscopy supplemented by energy dispersive spectroscopy. The test results showed that the intergranular and intragranular SCC fract ure of mild steel and alloy 430 in a H2S environment occurs only in the lim ited potential environment, whereas the alloys 316L and 317L are immune to SCC under the test conditions. The alloy Monel 400 was, however, found susc eptible to SCC in the presence of H2S, which may be present in somewhere in desalination plants due to the pollution of seawater.