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

Abstract

This paper describes a study of stress corrosion cracking (SCC) behavior of alloys resulting from the synergistic action of corrodents such as chlorides, oxidants and H 2S. In the this study the threshold stresses for SCC have been determined for a few generic alloys, namely mild steel, 316L, 317L, 430 and Monel 400, used in desalination plants. The standard Proof Rings and U-Bend samples in NACE and SHELL solutions containing H 2S were used for this purpose. Electrochemical polarization measurements were performed on these alloys in the specified environments to study the effect of electrochemical potential on intergranular SCC. Structural analyses were conducted by scanning electron microscopy supplemented by energy dispersive spectroscopy. The test results showed that the intergranular and intragranular SCC fracture of mild steel and alloy 430 in a H 2S environment occurs only in the limited potential environment, whereas the alloys 316L and 317L are immune to SCC under the test conditions. The alloy Monel 400 was, however, found susceptible to SCC in the presence of H 2S, which may be present in somewhere in desalination plants due to the pollution of seawater.