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Analysis and TEM examination of corrosion scales grown on Alloy 690 exposed to pressurized water at 325 °C
Author(s) -
Carrette F.,
Lafont M. C.,
Chatainier G.,
Guinard L.,
Pieraggi B.
Publication year - 2002
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1269
Subject(s) - autoclave , alloy , microstructure , materials science , corrosion , scanning electron microscope , x ray photoelectron spectroscopy , transmission electron microscopy , metallurgy , layer (electronics) , composite material , chemical engineering , engineering , nanotechnology
Corrosion scales grown on Alloy 690 during exposure to pressurized water were examined and analysed by SIMS, scanning electron microscopy (SEM), cross‐sectional transmission electron microscopy (XTEM), XPS and x‐ray diffraction at grazing incidence. All the corrosion tests were performed in pure water on spark‐machined and 1 µm polished specimens at a temperature of 325°C and a pressure of 155 bar. This surface finish results in the formation of a highly defective and thin perturbed zone similar to the standard surface finish of tubes used in pressurized water reactors. Two different testing devices were used: a static autoclave made of stainless steel and a recirculating autoclave made of titanium alloy. Scale thicknesses deduced from XTEM, XPS and SIMS are in good agreement; the average value is ∼50 nm for an exposure of 2160 h. The microstructure of these scales cannot be considered as duplex, as is usually described in the open literature. The scale is formed of a rather continuous and uniform internal Cr‐rich thin layer and an external layer, the composition, morphology and microstructure of which depend on the test conditions and test duration. For example, scales grown in the static autoclave contain higher concentrations of Fe and Ni than scales grown in the recirculating titanium alloy autoclave. Copyright © 2002 John Wiley & Sons, Ltd.