Electrochemical Investigation into the Effect of Nano-Titania on the Protective Properties of Epoxy Coatings on Mild Steel in Natural Seawater

Abstract

The effect of introducing nano-tinania (TiO 2 ) particles to the epoxy coatings on mild steel in natural seawater was analyzed using Scanning Electrochemical Microscopy (SECM) and Electrochemical Impedance Spectroscopy (EIS). Line profile and topographic image analysis were measured by applying -0.70 V and +0.60 V as the tip potential for the cathodic and anodic reactions, respectively. The tip current at -0.70 V for the epoxy coated sample with TiO 2 nanoparticles decreased rapidly due to cathodic reduction of dissolved oxygen. The EIS measurements were conducted in natural seawater after wet and dry cyclic corrosion test. The EIS measured the film resistance (R f ) and charge transfer resistance (R ct ) values which were increased by the addition of TiO 2 nanoparticles in the epoxy coating. SEM/EDX and FIB-TEM analysis showed that complex oxides of titania were enriched in corrosion products at the scratched area of the coated steel and confirmed the presence of the nanoscale oxide layers of titania in the rust of the steel. The formation of complex oxides of titania had a beneficial effect on the corrosion resistance of coated steel. Keywords Electrochemical investigation into the effect of nano-titania on the protective properties of epoxy coatings on mild steel in natural seawater 144Copyright: ©2017 Raj et al. Nanoparticles, owing to high specific surface area and small particle size, can enhance the corrosion resistance of the organic coatings by increasing the electrolyte pathways length. Inclusion of metal nanoparticles to the organic coating provides cathodic protection to the underlying substrate. They also provide barrier and passive protection by generating oxides at a later stage. The importance of nanomaterials compared to conventional micro sized pigments is mainly due to their small size and large specific surface area. The decrease in size of the particles causes mechanical properties enhancement of the coating. There are a large number of reports indicating that the anticorrosion properties of the polyurethane coatings can be markedly improved in the presence of nanoparticles. Citation9-16 Titanium oxide is highly corrosion resistant and provides a barrier protection which is stable over a wide pH range. It is not classified as dangerous for human health and for environment. This has shown interest in using titanium oxide in organic coatings in the corrosion protection of steel. SECM has been introduced to evaluate the localized corrosion process, since it provides electrochemical activity and topographic information about the surface reactions at the micrometer scale in aqueous environments. [17][18][19][20][21] The application of SECM has facilitated experiments on the solid/liquid interface because of its high spatial resolution and electrochemical sensitivity.In this study, SECM was used primarily to evaluate the effect of TiO 2 nanoparticles on the corrosion protection performance of an epoxy coating over mild steel in natural seawater. The tip current was detected during the cor...

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Flame Retardant and Anticorrosion Behavior of Multifunctional Epoxy Nanocomposite Coatings Containing Graphitic Carbon Nitride/Silanized HfO2 Nanofillers for the Protection of Steel Surface in Automobile Industry

“…HfO 2 films significantly inhibited corrosion of stainless steel (304 SS), outperforming TiO 2 and ZrO 2 films, according to Li et al The authors found no evidence of altered film thickness following an extended immersion in neutral, alkaline, or acidic solutions. Typically, 1–3 nm thick thin oxide films on the surface of stainless steels give them their exceptional corrosion resistance . Such a film grows within seconds or minutes in the natural environment.…”

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