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2021-09-21 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Arrighi Céline , Savall Catherine, Creus Juan, Olivier Marie-Georges , "Corrosion resistance improvement of Zn-Fe electrodeposits by hybrid inorganic-organic sol-gel films" 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) European regulations have led to replace sacrificial cadmium coatings by zinc-based alloys. The combination of zinc with nickel, cobalt or iron leads to sacrificial deposits presenting a lower galvanic coupling with steel substrate, thus improving the sacrificial protection. Despite their good properties in terms of corrosion resistance, Zn-Ni deposits tend to be replaced by more eco-friendly solutions, such as Zn-Fe alloys. The lifetime of metallic coatings in corrosive environments can be increased by several means. Among them, sol-gel (SG) films, and particularly hybrid inorganic-organic ones, are very attractive. The variety of organic functions on precursors leads to the formation of functionalized films (corrosion protection, hydrophobicity, etc). This type of coatings combined with Zn-Fe electrodeposits has scarcely been investigated. This work aims at evaluating by using different characterization techniques the corrosion resistance of Zn-Fe deposits protected by sol-gel coatings . Zn-Fe alloys (14 wt.% Fe) have been deposited on a low alloy steel substrate by electrodeposition from an additive-free bath composed of zinc oxide, ferrous gluconate and potassium hydroxide [1] using pulsed currents. A hybrid inorganic-organic sol-gel composed of TEOS, MTES and GPTMS precursors has been used and two precursors contents have been investigated. Sol-gel films have been considered differently depending on this content: as a pre-treatment for the lower one and as an autonomous protective barrier for the higher one. Scanning Electron Microscopy (SEM) was used on the surface and the cross-section of coated samples to estimate the covering of sol-gel films and their thickness. Zn-Fe/steel and SG/Zn-Fe/steel systems have been immersed in 0.1 M NaCl during 3 or 7 days depending on the formulation and Electrochemical Impedance Spectroscopy (EIS) tests have been periodically performed. The barrier properties of samples have been evaluated with Neutral Salt Spray (NSS) test. Pictures were taken to assess the development of corrosion products and to compare the delays of appearance of white and red rusts. The delay of appearance of corrosion products was considerably increased thanks to the presence of SG films. Moreover, this improvement in terms of corrosion resistance was also highlighted by EIS tests with an increase of two orders of magnitude of the low frequency modulus.