ABSTRACT

A polymeric hybrid anti-corrosion coating was developed with varying amounts of zinc and graphite nanoparticles. The systems were prepared by blending polyvinyl alcohol (PVA) with methyl cellulose (MC) and polyethylene glycol (PG) in various weight ratios of zinc and graphite nano powders to formulate H0, H1, H2, H3, H4, and H5 composites. Aluminium (AA1060, and AA6061) and steel (AISI304) samples immersed in 1.0 M NaOH and in the absence and presence of H0 – H5 inhibitor concentrations at ambient temperature. Immersion, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy Techniques were investigated. Data were obtained after different time intervals. The inhibitor structures were also applied on the pre-treated specimens and oven heated. Fourier Transform Infrared Spectroscopy, Thermographic Analysis, Nanoindentation, Atomic Force Microscopy, Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis investigations were conducted to obtain the best formulation. From these studies, the hybrid system H4 for the aluminium, and H2 for the steel coupons shows excellent properties. This study has demonstrated interesting correlations between thermal stability, plasticity and surface waviness with resistance to corrosion, and used to identify the critical performance of the synthesized inhibitor structures. The immersion results show that the corrosion rate with H0 – H5 was inhibited with increased concentration of inhibitors in the NaOH solutions than H5 without Zn and C nanoparticles. The average inhibitor efficiency with H4 is 77.2% on AA1060, 81.6% on AA6061, and 74.6% on AISI304 coupons. The electrochemical measurement results obtained show that corrosion rate in the presence of H0-H5 decreased as different concentrations of H0-H5 were added to the system, and with increase in exposure time as a result of protective film formed on the electrode surface. The Nyquist plots indicate that the diameter of the depressed semi-circle decreases as different concentration of H0-H5 were added to the solution to the system. The Langmuir isotherm, best described the systems used as established by their R-values. FTIR showed crosslinking between PVA, PG, and MC polymers, interspersing with zinc and graphite Nano particles. Structures with the ratio of 3:1 embedding of nanoparticles within the polymeric matrix is the most stable compound, discovered by the TGA. Hardness is related to the plasticity, 142.32pJ plastic deformation occurred in SA102 with 20.84% of indentation efficiency. Result, shows SA105 and SA102 hybrid films small hardness values of 20.06 and 21.09 MPa and significantly large stiffness of 0.023 and 0.021 mN/nm respectively with respect to other. The surface examination of the exposed samples reviews that a dense layer film and localized corrosion were observed in the absence of Zn and C doped films. These studies conclusively confirm that inhibitor H4, provided the best overall anti-corrosion development.