The Effect of Titania-Halloysite Nanotubes Nanocomposite Coatings on the Corrosion Behavior of 316L Stainless Steel Substrate in Ringer Solution

Titania-halloysite nanotubes (HNTs) nanocomposite coatings were electrophoretically deposited on the 316L stainless steel substrate. Two-component suspensions of titania and HNTs particles (different ratios of titania : HNTs wt% and constant particles concentration of 10g/l) in ethanol with 0.5g/l of polyethyleneimine (PEI) as the dispersant were used for electrophoretic deposition (EPD) experiments. EPD was performed at 60V for 10 and 60s using a two-electrode cell. Coatings were sintered in vacuum furnace and at 700˚C for 1h. Microstructural, element mapping and EDX analysis were performed on the coatings using a SEM. It was found that HNTs reinforce the microstructure of coatings and prevent from the cracking of coatings deposited from the suspensions with HNTs>25wt%. The corrosion rate of substrate coated at 10 and 60s using the suspensions with different ratios of titania: HNTs was measured by electrochemical polarization technique in Ringer solution and at 37˚C. The corrosion rate of substrates coated for 60s decreased as the HNTs content increased in the suspension due to the crack-free microstructure of prepared coatings. However, the corrosion rate of substrates coated at 10s increased as the HNTs content increased in the suspensions due to the less packing density and thickness of prepared coatings.