Saburo Shimodaira

XPS determination of compositions of alloy surfaces and surface oxides on mechanically polished iron-chromium alloys

Abstract Using the XPS technique, the compositions of the alloy surface and the surface oxide on mechanically polished iron-chromium alloys were studied. For quantitative analysis, the ratio of photo-ionization cross section of Fe 2p 3 2 electrons to that of Cr 2p 3 2 electrons was estimated as 1.35 for Al Kα 1,2 radiation. Assuming a homogeneous oxide layer, the thickness of the oxide layer and compositions of the alloy surface and the surface oxide were simultaneously determined. The results showed no enrichment of chromium or iron either in the oxide layer or the alloy surface. Results on binding energies were also given.

The mechanism of atmospheric rusting and the protective amorphous rust on low alloy steel

Abstract Atmospheric rusting of mild and low alloy steels was studied by means of infra-red and far infra-red spectrophotometries, X-ray and electron diffraction methods and scanning electron microscopy. The rusting process can be interpreted on the basis of a previously reported diagram for rust formation in aqueous solution. A large amount of amorphous matter in rust formed in semi-rural atmosphere was identified by infra-red and far infra-red spectra as amorphous ferric oxyhydroxide, FeO x (OH) 8–2x . The amorphous ferric oxyhydroxide rust on low alloy steel was dense and uniform, and contained a considerable amount of bound water. From these results it can be concluded that the amorphous ferric oxyhydroxide rust acts as a protective barrier against atmospheric rusting of the steels. Cu, P and Cr in low-alloy steels are inferred to favour the formation of crack-free, uniform rust layer and help to produce uniform amorphous ferric oxyhydroxide.

An XPS study of the passivity of a series of iron—chromium alloys in sulphuric acid*†

Abstract The composition and structure of passive films formed on a series of iron—chromium alloys in de-aerated 1M H 2 SO 4 were quantitatively studied by XPS. The chromium content of passive film increased drastically at ca . 13 %Cr of the bulk alloy composition, whereas no composition change was found in the surface of the substrate alloy immediately under the passive film. The high corrosion resistance of iron—chromium alloys with high chromium content is attributed to the protective nature of hydrated chromium oxy-hydroxide, which is the main constituent of passive films on the alloys containing chromium of 12.5 at. % or more.

The mechanism of atmospheric rusting and the effect of Cu and P on the rust formation of low alloy steels

The oxidation processes of fe (11) hydroxo-complexes to alpha, beta, gamma and delta feooh and magnetite, which are important products of steels, and the effect of copper and phosphorus ions on the oxidation of the fe (11) hydro-complexes in aqueous solutions have been investigated. The mechanism of atmospheric rusting deduced from the results obtained in the present investigation has been used to explain the difference in behavior between ordinary mild steels and low alloy steels during atmospheric exposure. It is concluded that fe (11) complexes are transferred to amorphous magnetite by the catalytic effect of cu and P present in steels. The amorphous magnetite forms a compact rust layer that enhances corrosion resistance of the steel. /TRRL/

ESCA study of the passive film on an extremely corrosion-resistant amorphous iron alloy

Abstract X-ray photoelectron spectroscopy was applied to study the composition of the passive film formed on an extremely corrosion resistant amorphous Fe-10at.%Cr-13at.%P-7at.%C alloy in 1 N HCl. The passive film consists mainly of hydrated chromium oxyhydroxide which is a common major constituent of passive films on crystalline stainless steels. The extremely high corrosion resistance of the amorphous alloy can only in part be attributed to the formation of a protective hydrated chromium oxyhydroxide film.

Characteristics of passivity of extremely corrosion-resistant amorphous iron alloys

Abstract The amorphous FeCrPC alloy was compared with the crystallized alloy having the same composition in potentiodynamic polarization curves and with an 18Cr8Ni stainless steel in current decay after abrading the specimens under anodic polarization. Through these results along with the previous ESCA study, the extremely high corrosion-rseistance of the amorphous iron alloys containing 8 at.% or more chromium has been interpreted in terms of the rapid formation of thick, uniform, highly corrosion-resistant passive film due to the characteristics of the amorphous alloys.

X-ray photoelectron spectrum of Fe2+ state in iron oxides

Abstract As a standard for identification of iron oxides by X-ray photoelectron spectroscopy, Fe 2+ spectra are extracted from mixed Fe 2 p 3/2 spectra of Fe 3+ , Fe 3+ and metallic states. The peaks of Fe 2+ spectra are all located at binding energy of 708·5 eV. The width of Fe 2+ spectrum seems to be dependent on crystallinity, and is 2·2 eV for a bulk crystalline oxide and 2·9 eV for an amorphous thin film under instrumental condition with FWHM of 1·3 eV for Au 4f 7/2 .

An ESCA study of the Fe2+/Fe3+ ratio in passive films on iron-chromium alloys

Abstract X-ray photoelectron spectra of Fe 2p 3 2 electrons are measured for passive films on iron and FeCr alloys passivated for 1 h in 1M H2SO4 at + 100 and + 500 mV (s.c.e.). When chromium content of FeCr alloys increased to ca. 12 at.%, binding energy of Fe 2p 3 2 electrons from oxidized state shifted abruptly from ca. 710·3 to ca. 709·6 eV and no more change in binding energy was observed at high chromium content. This abrupt shift of binding energy is in accord with the fact that the Fe2+/Fe3+ ratio showed sharp increase at ca. 12 at.% chromium. This phenomenon can be attributed to the inhibition of oxidation of iron due to the change in film structure and properties.

Hydrogen Electrode Reaction and Hydrogen Embrittlement of Mild Steel in Hydrogen Sulfide Solutions

Abstract Effects of strain rate, applied potential, pH, temperature, and hydrogen sulfide concentration on sulfide cracking of mild steel were examined at constant strain rates by means of an Instron-type machine. Fractographic observations were also carried out on a scanning electron microscope. Kinetic studies were also made to elucidate the hydrogen electrode reaction mechanism for mild steel and the effect of hydrogen sulfide on the reaction. Amount of hydrogen absorbed in mild steels stressed at a constant strain rate was measured and relationship of hydrogen embrittlement of mild steel with hydrogen electrode reaction and hydrogen absorption in hydrogen sulfide solutions was investigated. Fracture surfaces were transgranular quasi-cleavage and nucleation sites of cracks appeared to be carbides in the pearlite, inclusions and/or grain boundaries. The elementary reactions of hydrogen electrode reaction in acidic solutions are proton discharge and recombination of adsorbed hydrogen atoms and the rate d...

Formation of Fe(II)1Fe(III)1 intermediate green complex on oxidation of ferrous ion in neutral and slightly alkaline sulphate solutions

Abstract The formation of Fe(II)Fe(III)-intermediate green complex in aqueous solutions has been investigated. From the u.v. absorption spectra and the chemical analysis of neutral and slightly alkaline sulphate solutions of 5 × 10 −4 – 7 × 10 −4 mole/l iron at different pHs, the complex Fe(II) 1 Fe(III) 1 was found with the progress of aerial oxidation of Fe(II) species corresponding to FeOH + . The result has been used to estimate the iron composition of solid-green rust II. The participation of the green complex and green rust in the formation of Fe 3 O 4 and γ-FeOOH in corrosion process of iron in aqueous solutions was briefly discussed.