Electrophoretic deposition of halloysite nanotubes/PVA composite coatings for corrosion protection of metals

The application of nanotechnology in the corrosion protection of metals has gained considerable attention. In this work, a fast, low-cost, and facial method of metal protection was proposed by electrophoretic deposition (EPD) of halloysite nanotubes (HNTs). EPD is a standard method to prepare dense homogeneous polymers gaining wide application. HNTs exhibiting unique nanostructure, high surface potentials, and good dispersion ability were used as the different metals' coating materials. The coating thickness can be precisely controlled by changing the electrophoretic deposition conditions (time, concentration, electrode spacing, and voltage). Coatings of 50 μm thickness were achieved at conditions of deposition time of 30 s, HNTs concentration of 4%, electrode spacing of 30 mm, and voltage of 20 V. The HNTs coating can be applied to complex shapes and different metal types. To increase the water resistance, glutaraldehyde crosslinked polyvinyl alcohol (PVA) was further introduced to the coating. PVA modification increased the corrosion resistance, wear resistance, and water resistance. The surface roughness increased with the deposition time, as evidenced by SEM and 3D optical profiler. When the deposition time was increased from 15 to 60 s, the RMS roughness of the coatings increased from 1.46 to 2.82 μm. HNTs/PVA composite coatings on metals are used for thermal insulation, information hiding, and anti-corrosion. When the deposition time increased from 15 to 60 s, the coating resistance changed from 13,446.0 to 27,015.0 Ω cm2. This work developed an assembled method of nanoclays on metals by EPD and polymer modification, which shows excellent potential in metal anti-corrosion.