The effect of vapor grown carbon nanofiber-modified alkyd paint coatings on the corrosion behavior of mild steel

Vapor grown carbon nanofibers (VGCNFs) are a class of carbon fibers that are produced by catalytic dehydrogenation of a hydrocarbon at high temperatures. Depending on the method of synthesis and the post-treatment processes, the diameter of the VGCNFs is normally in the 10-300 nm range. The small size, light weight, high aspect ratio, and unique physical, thermal, mechanical, and electrical properties of VGCNF make it an ideal reinforcing filler in organic coatings and polymer matrix nanocomposites.;The main objective of the current investigation was to study the corrosion protection offered by the incorporation of VGCNFs into a commercial alkyd paint matrix applied to the surface of mild steel coupons. The corrosion protection was investigated by immersing samples in 3% NaCl solution. The samples were studied by electrochemical impedance spectroscopy (EIS) along with other measurements, including electrochemical (open circuit potential, cyclic voltammetry), chemical (salt spray test), electrical conductivity, and surface analysis techniques.;The study involved the investigation of the effect of the weight percent (wt %) of the VGCNF as well as the coating film thickness on the corrosion protection performance of the coated steel samples when exposed to the corrosive electrolyte. By way of contrast, the EIS behavior of steel coupons coated with a paint coating incorporating different weight percents of powdered silicon carbide (SiC) particles was also studied.;The electrical conductivity measurements showed that the incorporation of the VGCNFs or SiC microparticles in the alkyd paint formulation significantly enhances the electrical conductivity properties imparted by the coating. The nanoindentation measurements showed that the incorporation of VGCNF in the paint matrix improves the hardness up to 3%. On the other hand, increasing the SiC content improves the hardness of the paint matrix at all levels tested. The chemical and electrochemical measurements showed that VGCNF- and SiC-reinforced coatings are more stable than pure paint coatings.;Overall, the incorporation of a small amount of VGCNFs or SiC microparticles leads to significant improvements in the barrier properties of the paint matrix. Based on their anticorrosive properties, the three coatings systems are ranked as follows: VGCNF-reinforced coatings > SiC-reinforced coatings > pure paint coatings.