Osami Seri

The effect of NaCl concentration on the corrosion behavior of aluminum containing iron

Abstract Electrochemical measurements and metallurgical observations have been made to clarify the effect of NaCl concentration on the corrosion behavior of the intermetallic compounds such as FeAl 3 in aluminum. The preferential dissolution of iron in the intermetallic compounds and subsequently deposition of ferrous iron occurs in the dilute NaCl solution environment ( 3.0 M NaCl) the intermetallic compounds provide cathodic sites at which oxygen reduction reaction takes places. Dissolution of the intermetallic compounds is dependent on the variation of the corrosion potentials (open-circuit potentials); the corrosion potentials are equal to the pitting potentials related to the concentrated NaCl solutions.

The dissolution of FeAl3 intermetallic compound and deposition on aluminum in AlCl3 solution

Abstract Electrochemical and metallurgical investigations have been made to clarify the autocatalytic nature of aluminum corrosion in a pitting environment (de-aerated 1.0 M AlCl3). The dissolution of iron in the intermetallic compounds and subsequently deposition of the ferrous ions to metallic iron have been observed. It is explained that the autocatalytic nature is attributable to forming of galvanic couples between aluminum and the deposited iron in the pitting environment.

The interpretation of polarization curves for Al-Fe alloys in de-aerated NaCl solution

An attempt is made to explain the experimental evidence that the peak value of anodic current density, imax, occurs at −0.75 V (Ag/AgCl) in the polarization of Al-Fe alloys in de-aerated 0.1 M NaCl solution. It was found that this can be explained in terms of the anodic reaction which is the oxidation of iron in FeAl3 to ferrous hydroxide, Fe(OH)2. The iron formed as intermetallic compounds in Al-Fe alloys does not always provide an insoluble cathode in the aluminum matrix, but changes from iron into Fe(OH)2 under suitable solution conditions.

A Polarized Technique by an Increase of Cathodic Area for Detecting Pitting Attacks in Aluminum Galvanically Coupled to Tin

Abstract An effective electrochemical measurement called “area polarization technique” has been introduced in order to detect the occurrence of pitting attacks in 5052 aluminum alloy specimens that...

Ferroelectric and magnetic properties for nano particles of multiferroic YbFe2O4

ABSTRACT Size effect and lattice strain effect for charge ordered structure and magnetic properties were investigated on the nano particles of geometrically spin and charge frustrated system YbFe2O4. The lattice strain of the nano particle was controlled with the ratio of Yb and Fe (2.00 ≤ Fe/Yb ≤ 2.04) in liquid synthesizing method. It was found that the lattice strain is not affected by the magnetic transition temperature, however the anomalous behavior at a lower magnetic transition (TLT) with an increment of the Fe / Yb ratio was detected. The development of charge ordering was two-dimensional and magnetic ordering goes down for all samples in spite of the variation of the local lattice strain. This is the first report of the coupling of charge and spin ordering to the size effect in this material. These results suggest that the discussion on the electric polarization induced from the charge ordering in this material need to care the long-range interaction like surface effect.

Raman scattering study of microcrystals of perovskite titanates

ABSTRACT Microcrystals of several perovskite titanates (ATiO3, A:Pb, Mn, Ni, Co, Mg) have been synthesized by the corrosion product method. The products were characterized by XRD, SEM, and Micro-Raman scattering. The average size of the microcrystals is estimated to about 2 μm by the scanning electron microscope. Micro-Raman scattering spectra show the typical line shapes corresponding to the crystal structures of ATiO3. In the trigonal MgTiO3, the intensities of the several Raman modes take the maximum value at 50°C as temperature increase from room temperature. It is indicated that the peaks are caused by the impurities rather than the structural change.

Surface Treatment for Corrosion Resistant Aluminium Alloys by Removing Intermetallic Phases

It is well known that the Al-Fe system intermetallic compound particles on the aluminum and its alloys are detrimental to the corrosion for aluminum materials. Trial and error efforts reveal that Al3Fe intermetallic compound particles exposed on aluminum are preferentially and selectively removed by electrochemically treatment in cathodic current. These treatment combined by two steps: the first step is selective dissolution of aluminum component in the Al3Fe intermetallic compound by electrochemical reaction. The second step is intensive removal of the iron-enriched intermetallic particles on which vigorous hydrogen bubbling has been took place. The electrochemical measurement and surface observation show that the aluminum and its alloys with free intermetallic compound particles treated by aboves have excellent corrosion resistance in a NaCl solution. It is also found that the intermetallic compound-free surface is preferable for the pretreatment surface for the surface finishing.

Maximum anodic current on polarization curve for Al-Zn alloys.

An attempt is made to explain the experimental evidence that a peak value of anodic current density occurs at about -0.95V vs. Ag/AgCl in the anodic polarization curves of Al-Zn alloy specimens in deaerated 0.1M NaCl solution. It was found that this can be explained in terms of the anodic reaction which is oxidation of zinc element in the Al-Zn alloy specimen to zinc hydroxide.

An investigation on corrosion potential of Al-Fe alloys in AlCl3 solution.

Effects of iron on the corrosion potential and behavior of Al-Fe alloys corroded in deaerated 0.1 M AlCl3 solution were studied by electrochemical measurements. Iron in Al-Fe alloys in the form of intermetallic compound dissolves into AlCl3 solution and deposits on the surface of aluminum in the solution. The cathodic reaction of hydrogen evolution easily occurs on the surface of the deposited iron. The aluminum matrix therfore remains a pitting corrosion state, where the corrosion potential is equivalent to the pitting corrosion potential -0.78 V vs. Ag/AgCl.