The adsorption and corrosion inhibiting effect of aqueous extracts of Punica granatum (PNG) on mild steel in 1 M HCl and 0.5 M H 2 SO 4 at 30 ( 1 °C was investigated using gravimetric, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization techniques. The experimental findings revealed that PNG inhibited the corrosion reaction in both acid environments. Impedance results indicate that the extract organic matter was adsorbed on the metal/solution interface, while polarization data show that the extract behaved mostly as a mixed-type inhibitor. A theoretical study of the adsorption behavior of some of the components of the crude extracts was carried out in the framework of the density functional theory (DFT).

The adsorption and corrosion inhibiting effect of acid extracts of Piper guineense (PG) leaves on mild steel corrosion in 1 M HCl and 0.5 M H2SO4 was investigated using gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy techniques as well as scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The polarization and impedance results revealed that PG inhibited the cathodic and anodic partial reactions of the corrosion process via adsorption of the extract organic matter on the metal/solution interface. The mechanism of adsorption deduced from the variation of inhibition efficiency with temperature as well as kinetic and activation parameters suggest significant chemisorption of the extract constituents on the metal surface. Density functional theory calculations were performed to model the electronic structures of some extract constituents, including chemisorptive interactions with the Fe surface.

The inhibition properties of phytic acid (PA) on Q235 mild steel corrosion in 0.5 M H 2 SO 4 was estimated using electrochemical techniques. Polarization results revealed PA to be a mixed-type inhibitor in 0.5 M H 2 SO 4 , with a more pronounced cathodic effect, while impedance results indicate adsorption of the PA species on the steel surface. The values of the synergistic factor with KI were higher than unity indicating that both additives act cooperatively to improve inhibition performance. The adsorption of PA followed the Langmuir adsorption isotherm. The mechanism of chemical adsorption is proposed on the basis of the trend of inhibition efficiency with temperature and the calculated values of the activation energy (E a ). Scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy studies revealed the formation of a protective film adsorbed on a mild steel surface. Quantum chemical calculations were used to confirm the ability of phytic acid to adsorb on a steel surface.

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