Electrophoretic deposition of hybrid film on aluminium 2024 using sol–gel boehmite nanoparticles

Abstract

The realisation of organic/inorganic coatings on metal substrates, prepared by sol–gel route and shaped by electrophoretic deposition (EPD), is a new process which has been the subject of only few studies. In the past few years, EPD became a very interesting deposition technique because it showed some important advantages: i) great control of the deposition rate and ii) good coverage of complex shape parts. Both are the main challenges for all kinds of deposition techniques, used in various fields from anti-corrosion to anti-wear. In this work, the electrophoretic deposition was performed in aqueous sol suspension containing sol–gel boehmite nanoparticles (NPs). The influence of the applied voltage and deposition time on the deposit thicknesswas studied. The effect of the concentration of NPs, added in the precursor sol, on the thickness was also investigated. The deposition was performed at constant voltage between −1.2 and −3.5 V during constant deposition time between 10 and 40 min. It is shown that an increase in the applied voltage and deposition time increased the thickness of the deposit film (from2 to 11 μm), aswell as the amount of evolved hydrogen, resulting in a drop of the formed coatings quality (more porous structure). However, increasing the concentration of NPs in the precursor sol, increased the coating thickness and turned out to be also a key parameter to control the thickness. Finally, it was demonstrated that a perfect control of the microstructure and the deposit thickness was achievable, thanks to both EPD parameters and sol properties.