Electrochemical and Nanoindentation Study of Manganese Oxide Nano-Particles Mediation on Corrosion Retardation of Citrus Extract on Carbon Steel in 15% HCl

Nanoparticles (NPs) are the center of attraction in all branches of science, engineering and technology. Therefore, in corrosion science, it is expected that (NPs) will solve the problem of replacement of chromates through inhibitor modification. Among the electrochemical techniques employed for analyses were electrochemical noise (EN), cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR). Other characterization methods such as structural phase analyses with x-ray diffractometer (XRD), functional group analysis with Fourier Transform Infrared (FTIR) spectroscopy and nanoindentation were employed. The synthesized material was identified as nanoparticles by structural phase and UV-vis absorption analyses. All the electrochemical techniques manifested escalation of inhibition efficiency (Ζ %) at the introduction of the (NPs). Almost all the evaluated synergism constants (S<SUB>Q</SUB>) of each composite mixture of PECS and MnO<sub>2</sub>NPs achieved values which are above the threshold of one used to indicate whether synergism or antagonism took place. Nano-indentation with a scanning probe microscope (SPM) shows that the carbon steel encountered highest protection from degradation in 15 % HCl containing both PECS and MnO<sub>2</sub>NPs, followed by PECS and suffered the greatest degradation attack in the free acid medium. These results are full of prospects for a binary mixture of MnO<sub>2</sub>NPs+PECS to be used as non chromate corrosion retardant and indicate that this inhibitor modification approach can serve as a substitute to the use of banned cancer- causing and environmentally damaging chemical inhibitors.