Adherence measurements and corrosion resistance in primer/hot-dip galvanized steel systems

This paper focuses on the adherence during ageing of a primer (made of polyester resins crosslinked with melamine) applied onto hot-dip galvanized (HDG) steel for coil coating application and its influence on corrosion protection. A chromium-free surface treatment, composed of fluorotitanic acid, phosphoric acid, manganese phosphate, and vinylphenol was applied on the HDG steel to obtain high corrosion resistance and high adherence of a polyester and melamine primer. The influence of the manganese phosphate on the corrosion and adherence was investigated. To measure the adherence between the metal and the primer, a three-point flexure test was set up. The adherence was then linked with corrosion resistance during ageing, using electrochemical impedance spectroscopy

LES JOINTS INTERGRANULAIRES DANS LES MÉTAUX AUTODIFFUSION INTERGRANULAIRE DANS DES BICRISTAUX DE FLEXION D'UN ACIER INOXYDABLE AUSTÉNITIQUE, DÉSORIENTÉS AUTOUR DE L'AXE < 100 >

L'autodiffusion intergranulaire du Fe59 dans des bicristaux d'aciers austénitiques (16 % Cr-14 % Ni) a été étudiée d'une part en fonction de l'angle de désorientation θ dans la gamme de température 800-1 050 °C et d'autre part dans les deux directions parallèle et perpendiculaire à l'axe de flexion [001], afin de montrer l'effet d'anisotropie. Le rôle important joué par l'effet de l'asymétrie du joint a été aussi étudié par autoradiographie et mesures densitométriques. Une corrélation entre la diffusion, la corrosion et l'énergie des joints a été établie.The intergranular self diffusion of Fe59 in austenitic steels bicrystals (16 % Cr-14 % Ni) has been studied, both in fonction of the angle of misorientation θ, in the temperature range of 800-1 050 °C and in the two directions parallel and perpendicular to the axe of flexion, in order to examine the effect of the anisotropy. The important role played by the asymetry of grains boundary has been also studied by the technique of autoradiography through densitometric measurements. A correlation between diffusion, corrosion and grain boundaries energy has been established

RELATION BETWEEN ELECTROCHEMICAL REACTIVITY AND STRUCTURE OF GRAIN BOUNDARIES CORRELATED TO INTERGRANULAR SULFUR SEGREGATION IN ULTRA PURE NICKEL

Dans un nickel ultra pur dopé à 8 et 16 ppm de soufre, nous avons caractérisé la cinétique de ségrégation et l'état d'équilibre des joints de grains ségrégés en soufre grâce à un test de corrosion électrochimique. Le nickel de base et l'échantillon le plus ségrégé sont observés au microscope électronique à transmission afin d'établir un histogramme de la structure des joints de grains étudiés et de déterminer les paramètres cristallographiques des joints les plus chargés en soufre. Ces résultats sont corrélés avec la réactivité électrochimique et l'analyse quantitative en microscopie électronique à balayage à transmission.In a ultra pure nickel doped with 8 and 16 ppm of sulfur, we have determined the kineticsand equilibrium state of segregated sulfur at grain boundaries by electrochemical corrosion test. The undoped nickel and the highest segregated specimen are observed in transmission electron microscopy in order to correlate the structural histogram with electrochemical reactivity study and analytical scanning transmission electron microscope experiments

Simple procedure for vacant POM-stabilized palladium (0) nanoparticles in water: structural and dispersive effects of lacunary polyoxometalates

International audienceMetallic palladium nanoparticles have been generated by hydrogenation with H2 of solutions of several non organometallic PdII-derivatives of heteropolytungstates, at ambient temperature and atmospheric pressure. These nanoparticles have been characterized by various techniques: 31P NMR and Raman spectroscopy, TEM (including cryogenic techniques), DLS, EDX and XPS. The present strategy ruled out the presence of ligands and/or stabilizing agents other than the lacunary polyoxometalates (POMs) used. This allows the evaluation of the true efficiency of the different vacant POMs for the stabilization of the nanoparticles

Structural study of radiolytic catalysts Ni-Ce/Al2O3 and Ni-Pt/Al2O3

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Comparison of the conventional impregnation method using ammonium heptamolydate with a simple route to silica-supported molybdenum(VI) materials.

International audienceSilica-supported molybdenum oxide materials have been prepared by using the ability of molybdenum oxoperoxo complexes to interact with the surface hydroxyl groups of the support, which after calcinations, have a highly dispersed MoOx/SiO2 structure, and lead to leach-resistant catalysts; with a polyoxo precursor, (NH4)6[Mo7O24].4H2O, there is a formation of MoO3 clusters and a weaker MoO3/SiO2 interaction

Multidisciplinary study of the Wealden deposits in the Mons Basin (Belgium): a progress report.

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