Pre-oxidation of stainless steel: a study by diffuse reflection spectroscopy (original) (raw)
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Optical reflection spectroscopy of thick corrosion layers on 304 stainless steel
Corrosion Science, 2007
Corrosion resistant structural materials of both iron and nickel based alloys are used in the electric power industry for the construction of the coolant loops of both conventional and nuclear power generating stations. These materials, in the presence of high temperature (e.g. 287° C), high pH (e.g. 10.0 @ 20°C) water with dissolved hydrogen will oxidize and form corrosion films that are double metal oxides (or spinels) of the form AB 2 O 4. This work describes optical reflectivity techniques that have been developed to study the growth of these films in situ. The optical technique uses a dualbeam specular reflection spectrometer to measure the spectrum of reflected light in small angle (i.e. < 15°) scatter. The reflection spectra are then calibrated using a set of corrosion coupons with corrosion films that are well known. Results are compared with models based on multilayer reflection and Mie scattering from a particle size distribution. Surface roughness is found to be the dominant cause of reduced reflection as the films grow.
Influence of surface preparation on oxidation of stainless steels at high temperature
Surface and Interface Analysis, 1993
Fourier transform infrared specular reflectance spectra at variable incidence have been recorded in order to characterize the oxide layers formed on both mechanically polished and etched surfaces of stainless steels (AISI 304 and 316). Depending on the surface preparation, the major oxides are either Cr2O3 and MnCr2O4 for polished samples or α-Fe2O3 and Fe3O4 for etched samples in the early stages of the oxidation in air at 900°C. Secondary ion mass spectrometry depth profiles confirm the schematic structure of oxide films (developed on polished surfaces during longer exposures) deduced from infrared reflectance study.
Oxidation of Metals
The effect of p(H 2 O) and p(H 2) on the oxidation of 304L stainless steel at 600°C has been investigated in the present study. The samples were analysed by means of X-ray diffraction, Auger spectroscopy, and scanning electron microscopy equipped with energy dispersive spectroscopy. The results showed that at fixed p(H 2), the corrosion rate increased considerably with increasing p(H 2 O). At fixed p(H 2 O), the corrosion rate decreased slightly with increasing p(H 2). Duplex oxide scales formed during the exposure in all environments. The outer and inner layer consisted of Fe 3 O 4 and (Fe, Cr) 3 O 4 , respectively. The latter was mainly in the form of internal oxidation. The Cr-rich oxide formation was observed at the initial oxidation process before oxide breakdown. The Auger analysis also suggested the presence of Cr-rich oxide layer just after the breakaway oxidation. The results indicated that the rate-determining step in the corrosion attack is surface controlled or diffusion controlled through an oxide layer with fixed thickness over time.
Journal of physics, 2016
Different thermal treatments were performed for the anti-oxidation of steel surfaces, and the processes were investigated ex-situ and in-situ by surface sensitive reflection mode EXAFS experiments at the Cr and Fe K-edges. While the samples for the ex-situ studies were heat-treated in a conveyor belt furnace at temperatures between 600 and 900 °C in inert carrier gases (N 2 or Ar) using different additives such as hydrogen (H 2) and monosilane (SiH 4), the insitu anti-oxidation treatments have been performed in a high vacuum environment (p < 10-6 mbar). While the ex-situ experiments suggest that SiH 4-additives are needed for the reduction of the steel to a metallic state, the in-vacuum treatments appear successful for temperatures above approx. 900 °C.
Stainless steels of type SUS304 and SUS316 were chemically treated and heated at various temperatures, and the oxide films formed on the surface were analysed by Auger electron spectrometry and conversion electron M6ssbauer spectrometry. The outermost oxide layers of stainless steels were enriched with iron and chromium after heat treatment below 600 ~ C and above 700 ~ respectively. It was found that at least two magnetic components of iron species were present in the oxide layers of stainless steel heated below 600 ~ C and that the fine particles of iron oxide are produced in the inner oxide layers of the samples prepared by heating at temperatures higher than 700 ~ C. Only paramagnetic iron species were detected in the oxide layers of the stainless steel prepared by chemical treatment. The structures of the oxide layers produced by those heat and chemical treatments are proposed.
Journal of Materials Science, 1990
Stainless steels of type SUS304 and SUS316 were chemically treated and heated at various temperatures, and the oxide films formed on the surface were analysed by Auger electron spectrometry and conversion electron M6ssbauer spectrometry. The outermost oxide layers of stainless steels were enriched with iron and chromium after heat treatment below 600 ~ C and above 700 ~ respectively. It was found that at least two magnetic components of iron species were present in the oxide layers of stainless steel heated below 600 ~ C and that the fine particles of iron oxide are produced in the inner oxide layers of the samples prepared by heating at temperatures higher than 700 ~ C. Only paramagnetic iron species were detected in the oxide layers of the stainless steel prepared by chemical treatment. The structures of the oxide layers produced by those heat and chemical treatments are proposed.
Development of the inner oxide zone upon steam oxidation of an austenitic stainless steel
Materials at High …, 2009
The oxidation behaviour of TP 347H FG in mixtures of water, oxygen, and hydrogen was investigated in the temperature range 500 -700 C for a fixed oxidation time of 336 h. The samples were characterised using reflective light and electron microscopy methods. Thin discontinuous double-layered oxide scales developed during oxidation at 500 C, whereas continuous doublelayered oxide scales covered the entire sample surface after oxidation at 600 and 700 C. The major part of the scale grew into the former alloy grains, whereas Fe2 2Cr spinel grew along the former alloy grain boundaries. TEM and EELS investigations revealed that the part of the scale that grows into the alloy grains consists of particles of Fe2 2Cr spinel embedded in a metallic Fe2 2Ni matrix, which indicates that this part of the scale grows by an internal oxidation mechanism. Growth of the internal oxidation zone at high humidity (46%) is not significantly affected by the type of carrier gas used.
Effect of surface finishing on the oxidation behaviour of a ferritic stainless steel
Applied Surface Science, 2017
The corrosion behaviour and the oxidation mechanism of a ferritic stainless steel, K41X (AISI 441), were evaluated at 800 • C in water vapour hydrogen enriched atmosphere. Mirror polished samples were compared to as-rolled K41X material. Two different oxidation behaviours were observed depending on the surface finishing: a protective double (Cr,Mn) 3 O 4 /Cr 2 O 3 scale formed on the polished samples whereas external Fe 3 O 4 and (Cr,Fe) 2 O 3 oxides grew on the raw steel. Moreover, isotopic marker experiments combined with SIMS analyses revealed different growth mechanisms. The influence of surface finishing on the corrosion products and growth mechanisms was apprehended by means of X-ray photoelectron spectroscopy (XPS) and residual stress analyses using XRD at the sample surfaces before ageing.
Effects of hydrogen peroxide on 304 stainless steel in high temperature water
Journal of Physics: Conference Series, 2019
Hydrogen peroxide (H2O2), an oxidizer produced by water radiolysis, is considered one of the main contributors to corrosion of the stainless steel (SS) components in the cooling system of nuclear reactors. The detailed understanding of this chemical system is however still missing. The present research aimed to study the effects of H2O2 on 304 SS. The surface morphology and the chemical composition of the SS specimens after experiment were examined using Scanning Electron Microscope – Energy Dispersive X-ray (SEM-EDX). The change in atomic % of Fe, Cr, Ni, and O as a function of temperature will be reported. The corrosion type and possible corrosion products will be proposed and discussed.
Journal of Colloid and Interface Science, 2008
The evolution of the surface of a conventional stainless steel (AISI 316L) immersed in aqueous medium simulating fresh water (pH ∼8) was studied using XPS and AFM. A detailed analysis of XPS spectra allowed a distinction to be made between oxygen of organic and inorganic nature. During the first 48 h, the main changes concern the inorganic phase: the oxygen concentration in the passive layer increases, owing both to oxidation of metal elements, including conversion of Fe II to Fe III , and to hydration; the molar ratio of oxidized species Fe ox /Cr ox decreases slightly; the formation of colloidal particles, presumably made of ferric hydroxide, is observed by AFM. After longer periods of immersion, the Fe ox /Cr ox is higher, while the coating of colloidal particles reaches a full surface coverage. The amount of organic compounds increases further and the XPS spectra reveal the accumulation of polysaccharides and proteins, which indicate that these organic compounds are of biological origin.