Dépôt d'oxyde de silicium par procédé plasma hors équilibre à basse pression et à pression atmosphérique sur de l'acier : application aux propriétés anticorrosion

Abstract : The aim of this study was the development of two surface treatment processes for the improvement of the corrosion resistance of steel (HLE S235). Silicon oxide films (SiOxCy) were deposited on steel substrates by plasma enhanced chemical vapor deposition (PECVD) at low pressure as well as at atmospheric pressure. Hexamethydisiloxane (HMDSO), which is an organosilicon, was the precursor. These films show very good protection and adhesion properties to steel. Gas and liquid permeability performances of coatings deposited by plasma (PECVD) are very strongly linked to their chemical composition (presence of carbon, absence of silanol) and structure (thickness, density, free volume?). These directly depend on the conditions of polymerisation process. That means it depends on the plasma parameters such pressure, power, monomer mass flow, time of treatment? Analysis about deposit morphology and its composition were necessary to characterize the deposits. We were able to obtain thick, continuous, smooth, not very porous layers, containing some carbon. The efficiency of the deposition processes of silicon oxide was validated by the study of corrosion protection properties of films by voltamperometry and electrochemical impedance spectroscopy in an aerated NaCl 0,5 M solution. For optimal conditions of treatment, in low pressure as well as in atmospheric pressure, the corrosion protection were much improved and remained constant for long immersion times (Rp stabilized after 25 h). Low pressure oxygen pretreatment allowed to increase the adhesion of the coatings to the substrate and thus the corrosion protection for the films realized at low pressure and at atmospheric pressure. The polarization resistances thus obtained reached the value of 191 kOhm.cm² and 550 kOhm.cm², respectively (untreated steel: 1,2 kOhm.cm ²).
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Contributor : Camille Petit-Etienne <>
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Camille Petit-Etienne. Dépôt d'oxyde de silicium par procédé plasma hors équilibre à basse pression et à pression atmosphérique sur de l'acier : application aux propriétés anticorrosion. Matière Condensée [cond-mat]. Chimie ParisTech, 2007. Français. ⟨tel-00367151⟩

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