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The statistical and theoretical view on mild steel (MS) corrosion in a sulphuric acid medium in the presence of leaves extract of Mussaenda frondosa (MF) were studied by electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The nature of the inhibitor was defined by the polarization studies. The semicircle curves observed in electrochemical impedance spectroscopy indicated that the corrosion of mild steel is controlled by the charge transfer process. The corrosion inhibition performances enhanced by the addition of MF extract and increase with increase in the concentration of the MF extract. GCMS is used to gather the important phytochemical constituents in the MF extract. The adsorption of MF on the metal surface is confirmed by SEM images. DFT was performed in order to confirm the adsorption of the constituents in MF extract on MS.

Moringa oleifera gum exudate a non-toxic organic compound, is introduced as a synergist to 3,5-Dimethyl-2,6-diphenylpiperidin-4-one and the corrosion inhibition of mild steel in the Hydrochloric acid medium is studied using weight loss method, potentiodynamic polarization and electrochemical impedance spectroscopy. Results show that 3,5-Dimethyl-2,6-diphenylpiperidin-4-one alone provided an average inhibition of the corrosion of mild steel and it was found that the inhibition efficiency increased synergistically in the presence of Moringa oleifera gum exudate. The inhibition efficiency increased with increase in the concentration of the inhibitor but decreased with a rise in temperature. Polarization studies reveal that the inhibitor system is of a mixed type. Impedance studies point out that a protective film is formed on the mild steel surface in the presence of the inhibitor. Fourier transform infrared spectroscopy and scanning electron microscopy studies were used to investigate the nature of protective film formed on the mild steel surface.

The corrosion protection of aluminium surface by the inhibitor 3, 5-diethyl 2, 6-diphenyl p-chloro Piperidin-4-one in 1N Sulfuric acid medium is examined by using mass loss measurement. Electrochemical studies are used to analyze the corrosion inhibiting nature of the inhibitor. The experimentation is carried out at room temperature. The findings of mass loss measurement indicate that the studied organic inhibitor molecule exhibit corrosion inhibition efficiency on aluminium in sulfuric acid medium. The findings of polarization studies show that inhibitor 3, 5-diethyl 2, 6diphenyl p-chloro Piperidin-4-one behaves as both anodic and cathodic type corrosion inhibitor. From the increasing value of charge transfer resistance (Rct) with decreasing nature of double layer capacitance (Cdl) value the corrosion inhibiting nature is observed to increase with the increase of inhibitors concentration at constant acid strength. The adsorption of the inhibitor 3, 5-diethyl 2, 6-diphenyl p-chloro Piperidin-4-one on aluminium obeys Langmuir's adsorption isotherm.

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