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Etude de la durabilité d'un primaire epoxy anticorrosion : rôle de l'interphase polymère/métal et conséquence sur l'adhérence

Abstract : The organic coatings durability is an important industrial and scientific topic. The life time of an anticorrosion coating depends mainly on its adhesion on the metallic substrate. The aim of this work consists in indentifying the interphase area and understanding its influence on adhesion between an anticorrosion coating and a metallic substrate. We try also to validate experimental parameters for following coating deterioration, as well as the development of corrosion or delamination at the metallic interface during immersion. These protocols may be use to predict the coatings durability. A no filled coating with different stoichiometries and a commercial primer are studied. Both are based on the same polymer binder DGEBA-Polyamidoamide. The anticorrosion coating is formulated with a vinyl terpolymer, ferrous oxide and zinc phosphate as anticorrosion pigments and talc as main filler. Different methods are used to characterize the interphase area in the DGEBA / Polyamidoamine systems applied onto steel: the Fourier Transformed Infra Red spectroscopy (FTIR), the Micro Thermal Analysis (µTA) and a method based on deflexion measurements. We have observed differences of behaviour between the properties of the interphase and those of the bulk one. The inherent limits of the characterization by deflexion measurements drive to overestimate the thickness of the interphase. The characterizations by IR and µTA have allowed observing the interphase to a smaller scale. We have then observed by IR a strong presence of amine in an interphase are a which thickness is about 40 µm. This strong concentration of amine is also confirmed by µTA results, that drive to a reduction of Tg from the bulk to the metallic interface. Different samples have suffered a hygrothermal artificial ageing test, which involved modifications of the interphase. Moreover, a study by Electrochemical Impedance Spectroscopy (EIS) is performed in order to characterize evolutions of protection properties. For that, measurements of pore and charge transfer resistances as coating capacitance have been carried out as a function of immersion and hygrothermal ageing times. Their evolutions have shown 3 stages for loss of protection properties, and also the control of phenomena at the metallic interface by barrier properties. Finally, adhesion measurements of the coatings on the metallic substrate complete and confirm previous results. They precise the beneficial effect of the amine on the adhesion and also on the reversibility of that adhesion after drying.
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Thi Hai Yen Qhach. Etude de la durabilité d'un primaire epoxy anticorrosion : rôle de l'interphase polymère/métal et conséquence sur l'adhérence. Polymères. Université du Sud Toulon Var, 2010. Français. ⟨tel-00647580⟩

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