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2021-09-20 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Pham Thu Thuy , Nguyen Thuy Duong, To Thi Xuan Hang, Olivier Marie-Georges , "A comparative study of structure and corrosion resistance of ZnAl hydrotalcite conversion layers obtained at different pH and Zn/Al ratio on electrogalvanized steel" in EUROCORR2021, Virtuel (Budapest), Hongrie, 2021

  • Codes CREF : Enseignement des sciences de l'ingénieur (DI0132), Corrosion des matériaux (DI2114)
  • Unités de recherche UMONS : Science des Matériaux (F502)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Ingénierie des matériaux (CRIM)

Abstract(s) :

(Anglais) The dissimilarities of the composition, crystal structure and corrosion resistance of ZnAl-HT conversion film grown directly on electrogalvanized steel substrate (EG steel) at solution pH 3.2 and 12.0 were investigated in the present work. While ZnAl-HT conversion film was developed on EG steel substrate by the hydrothermal method at the pH 3.2, the ZnAl-HT film formed at pH 12.0 was synthesized by in-situ growth method at different Zn/Al ratios. The corrosion resistance of all conversion films in 0.1 M NaCl solution was compared through polarization curves and electrochemical impedance spectroscopy. The polarization curves indicated that the ZnAl-HT films provided anodic inhibition for EG steel substrate and the inhibition efficiency of the conversion films grown at pH 12.0 was higher than that at pH 3.2. The reason for the dependence of corrosion resistance on solution pH was discussed from the viewpoints of composition, morphology and the structure of resulting conversion films characterized by reflex infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electronic microscopy (SEM) and electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). The results show that the conversion film formed at pH 3.2 consisted mainly of ZnAl-NO3 HT and some hybrid peaks of ZnO, Al(OH)3. In contrast, the unique ZnAl-CO3 conversion film consisting of more uniform hexagonal nano-plates was formed at pH 12.0. Key words: hydrotalcite conversion layer, electrogalvanized steel, corrosion resistance.