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Résumé :
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In this work, we have studied two main objectives. The first is the study of the influence of current density on the deferent characteristics of Ni-P coatings. The deposits are obtained by the technique of electroplating on a steel substrate. The experimental procedure has been optimized to ensure reproducibility of results and to minimize contamination of deposits. Different characterization techniques such as: adhesion quality, scanning electron microscopy (SEM) followed by microanalysis (EDS), X-ray diffraction (XRD), microhardness and corrosion resistance by two techniques (the lost mass method and potentiodynamic polarization) followed by electrochemical impedance spectroscopy (EIS) were implemented to better characterize the Ni-P deposits thus produced. The second objective was to study the inhibitory efficiency of two organic compounds on nickel-phosphorus coatings in a 1 M hydrochloric acid solution; we used several experimental methods, such as lost mass, polarization curves (Tafel method) and electrochemical impedance spectroscopy. To appreciate the adsorption mechanism and the behavior of different compounds on the metal surface, we calculated the correlation coefficient R2 using various adsorption isotherm models. The results demonstrate that the deposits obtained are adherent, smooth, amorphous 5 A.dm-2 exhibits the superior and uniform and the coatings deposited at a current density of microhardness and the best corrosion protection coating. On the other hand, the study of the inhibitory efficiency of sulfur compounds against corrosion of Ni-P coating coated at 5 A.dm-2 shows that the two sulfur compounds are good inhibitors and are in good agreement, an optimal efficiency. With the concentration 6.10-5 mol / l which is of the order of 98.12% and 97.83% successively for the inhibitor (A) and (B), the adsorption of the molecules of the inhibitors corresponds to the isotherm of Langmuir adsorption, these inhibitory molecules followed chemical adsorption (chemisorption) to the surface of the Ni-P alloy.
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