Evaluation of the Corrosion Barrier Properties of Nano-Reinforced Vinyl Chloride/Vinyl Acetate Coatings

A poly(vinyl chloride/vinyl acetate) copolymer (VYHH) with and without multiwalled carbon nanotubes (MWCNTs) as reinforcements were used as a coating for steel substrates to evaluate their barrier properties against corrosion. Electrical impedance and thermal properties of the coatings were evaluated. The coatings were formulated with 0.1% MWCNT, by weight. Neat and nano-filled VYHH was used to coat polished, degreased steel substrates via a dipping method. The substrates were either dipped once, for a target coating thickness of 30-40 mu m, or twice for a target coating thickness of 60-75 mu m. The coated and uncoated control samples were submerged in a tank with a 5% NaCl solution for a 45-day period. Electrochemical impedance spectroscopy (EIS) revealed that coating thickness plays a role in corrosion resistance. EIS also showed that nano-reinforced VYHH had the highest charge transfer resistance within its coating thickness. Fourier transform infrared spectroscopy (FTIR) indicated that hydrolysis occurred in the single coatings for both the neat and nanoreinforced coatings. Differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) both showed that the addition of MWCNTs improved the thermal stability of the VYHH. DSC thermograms revealed that the thermal properties of the nano VYHH were largely unchanged after 45 days of submersion as compared with the unaged nano VYHH. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 15-22, 2011