Publications Internationales
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Item The effect of inhibiting molybdate used in anodizing-conversion treatment to improve corrosion protection of AA2030 aluminum alloy in different steps(Springer, 2022) Benmohamed, Manel; Benmounah, Abdelbaki; Haddad, Ahmed; Yahi, SarahIn this article, different treatment baths for corrosion protection of 2030 aluminum alloy in addition to replacing the hexavalent chromium due to the European recom- mendation were employed. This work is divided into three steps of treatment: first, anodization using molybdate inhibitor without and with phosphoric acid and, then, pre-oxidation with sodium hydroxide. In the last step, we studied the influence of conversion coating with the combination of sodium molybdate and fluoride on the anodic layer formed on aluminum alloy 2030. In order to characterize the formed lay- ers, we use microstructural characterization (SEM, AFM, and nano-indentation), which allows highlighting the surface condition as well as the morphological distribution, and electrochemical techniques such as potentiodynamic polarization and electro- chemical impedance spectroscopy which shows that the anodization treatment of the aluminum alloy with phosphoric acid and sodium molybdate offered better corrosion resistance. This resistance increased with the use of pre-oxidation and then reached a maximum value of 99.8% efficiency with the addition of the molybdate conversion coating which causes an increase in the double layer and gave an alternative possibility of chromium VIItem Physical properties of the delafossite CuCoO2 synthesized by co-precipitation /hydrothermal route(Elsevier, 2021) Bouakaz, H.; Abbas, Moussa; Brahimi, R.; Trari, M.CuCoO2 crystallizing in the delafossite structure was prepared by co-precipitation/hydrothermal method at low temperature (~ 150 °C). It is stable in air up to ~400 °C beyond which it turns into the spinel. The oxide has a direct optical transition attributed to the crystal field splitting of Cu+, linearly coordinated. It exhibits p-type behavior due to O2− insertion in the layered lattice. Such property is corroborated by a cathodic photocurrent in the intensity-potential (J – E) plot and a negative slope of the capacitance potential (C−2– E) plot. The latter traced in NaOH (0.01 M) electrolyte, exhibits a straight line from which a flat band potential of +0.411 V and a hole density of 6.9 × 1023 m−3 were extracted. An exchange current density of 7.36 μA cm−2and a polarizarion resistance (6.69 kΩ cm2), derived from the semi-logarithmic curve (log(J) – E), indicate a good electrochemical stability with a medium hysteresis loop and a low H2-over potential. The anisotropy of the 2 D dimensional crystal structure allows reversible oxygen insertion in the (0 0 n) planes evidenced from the (J – E) profiles. The Electrochemical Impedance Spectroscopy (EIS) measurements give two well-distinguished depressive semicircles in the dark. The diameter of the semicircle at high frequencies (1.49 kΩ cm2) decreases down to (1.28 kΩ cm2) under irradiation, a behavior typical of a non-degenerate semi conductivity of CuCoO2Item The effect of surface treatments on the electrochemical behavior of titanium alloy in seawater by electrochemical impedance spectroscopy (EIS)(2015) Ghemmit-Doulache, Naima; Benserradj, S.Seawater contains many minerals, dissolved gases, including oxygen O2 cellular organisms, suspended solids and sediments that sometimes impart high turbidity. Chemical and biological characteristics of seawater make it a particularly aggressiv materials in particular titanium. Physico-chemical interactions between a metal material and its environment can lead to corrosion of material. Deterioration of metal due to microbial activity is called biocorrosion or corrosion induced by microorganisms (CIM). Because of its economic and environmental importance, CIM has been extensively over past five decades and several models studies have been proposed to explain the mechanisms biocorrosion observed. Many sectors are a facilities, plant thermal (heat exchangers). Biofilm formation on walls of conduits considerably reduces heat transfer, this is particularly important in case of heat exchanger tubes. We noted that electrode moves corrosion potential to more cathodic values. And more, the short stay of titanium in natural seawater, corrosion potential varies around - 250 mV/Ag/AgCl, and then it reaches less cathodic values to longer residence time. Electrochemical impedance measurements showed the presence of one loop relative to the capacitive charge transfer phenomenon of metal/passive layer. Keywords: Natural seawater, Titanium, OCP, Electrochemical impedance spectroscopyItem The influence of the second fusion on the microstructue and electrochemical behaviour of Algerian zinc(European Journal of Scientific Research, 2006) Bounoughaz, M.; Salhi, E.; Dalard, F.; Ghali, E.Zinc from the Algerian metallurgy industry (zinc A) was compared with specimens of the same zinc following fusion treatment at 500°C for 60 minutes and cooling according to three different kinetics. The treated materials are designated by B, C, and D. The fusion/cooling treatment modified the microstructural state of the metal. The different microstructural states were revealed by X-ray diffraction. Electrochemical studies of the treated zinc specimens were performed using voltammetry, potentiometry and electrochemical impedance spectroscopy (EIS). Only a significant variation in EIS results was found. The EIS diagrams of the materials varied with immersion times. The variations in low frequency resistance were directly correlated with the microstructural states of the specimens. The results of the study indicate that fusion treatment at 500°C for 60 minutes and cooling by nitrogen to 10 l min-1 is the most suitable for use as a sacrificial anode. © EuroJournals Publishing, Inc. 2006