Role of the Hybrid Addition of Carbon Nanotubes and Graphene Nanoplatelets on the Corrosion Behavior of Plasma-Sprayed Aluminum Oxide Nanocomposite Coating

The effect of synergistic reinforcement of two types of carbon nanofillers, carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), on the corrosion behavior of plasma-sprayed alumina (Al2O3) nanocomposite coating in 3.5 wt% NaCl solution is studied. Incorporation of 1 wt% CNT and 0.5 wt% GNP into the Al2O3 matrix reduces the corrosion current density of the matrix from 2.78 to 0.21 mu A cm(-2), which drastically leads to a 13 times reduction in the corrosion rate of the Al2O3 matrix as compared with pure Al2O3 coating. The plausible reasons to this improvement are characterized by the filling of gaps, crevices, and microholes in the Al2O3 matrix by CNTs and GNPs and hydrophobic nature as well as chemical inertness of these reinforcements to the aggressive environment. Further, the corrosion products are analyzed by X-ray diffraction and Raman spectroscopy for a much deeper insight into the mechanism of corrosion protection by these carbonaceous reinforcements. For the first time, the effect of CNT and GNP reinforcement on the corrosion behavior of plasma-sprayed coatings is investigated.