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The Mentha Piperita essential oil (MPEO) rich in anthraquinone,1-(p-fluorophen) as major compound (42.8 %) has been investigated as corrosion inhibitor for mild steel in 1 M HCl. weight loss, polarization curves (Tafel, Stern & Geary as well as Stern methods) and electrochemical impedance spectroscopy measurements were used to evaluate the inhibition performance of MPEO. The results obtained from different techniques were in best accord. The inhibiting efficiency, reaching circa 87 % at 0.7 g L-1 of MPEO, was found to increase with rise of inhibitor concentration, whereas the increase of temperature was in favour of its slow decrease. The adsorption data fitted well to Langmuir isotherm model and involved both physisorption. Scanning electron microscopic results testified the formation of a protective film onto the mild steel in the presence of MPEO.

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Statistical modeling of the corrosion inhibition process by twenty-one pyridazine derivatives for mild steel in acidic medium was investigated by the quantitative structure property relationship (QSPR) approach. This modeling was established by the correlation between the corrosion inhibition efficiency ( IE % ) and a number of the electronic and structural properties of these inhibitors such as: the E HOMO (highest occupied molecular orbital energy), the E LUMO (lowest unoccupied molecular orbital energy), the energy gap ( E L-H ), the dipole moment ( μ ), the hardness ( η ), the softness ( σ ), the absolute electronegativity (χ), the ionization potential ( IP ), the electron affinity ( EA ), the fraction of electrons transferred ( ΔN ), the electrophilicity index ω the molecular volume ( V m ), the logarithm of the partition coefficient ( Log P ), and the molecular mass ( M ), in addition to the inhibitor concentration ( C i ). The structure electronic properties was calculated by the use of the density functional theory method (DFT), at B3LYP/6-31G (d, p) level of theory and the analysis of dimensionality and redundancy as well as the test of collinearity between descriptors are carried out using principal component analysis (PCA). Whereas, the correlation between EI % and molecular structure is performed through the development of tree mathematical models, based-QSPR approaches: the partial least squares regression (PLS), the principal component regression (PCR) and the artificial neural networks (ANN). Indeed, the statistical quantitative results revealed that PCR and ANN were the most relevant and predictive models in comparison with the PLS model. This pertinence was demonstrated by using leave one-out cross-validation as an efficient method for testing the internal stability and predictive capability of said models with a high cross-validated determination coefficient R 2 cv = 0.92 and predicted determination coefficient R 2 pred = 0.92 and R 2 pred = 0.90 for PCR and ANN respectively; in addition to an extrapolation test set as an external validation with a significant external coefficient of determination: R 2 test = 0.94 and R 2 test = 0.92 , for the two correspondingly models.

The synergetic effects between hydroethanolic extracts of A. visnaga HE (AV) and Z. mays hairs HE (ZM) on corrosion of mild steel in 1 M HCl solution was investigated at 298 K by two techniques: potentiodynamic polarization (PP) methods (Tafel and Stern & Geary) and electrochemical impedance spectroscopy (EIS). The mixture of HE (AV)/HE (ZM) acted as an efficient corrosion inhibitor and its inhibition efficiency increased with concentration up to 96.55% at 0.01 gL−1 HE (AV)/0.2 gL−1 HE (ZM). The polarization curves revealed that the mixture acted as a mixed-type inhibitor, with anodic predominant action. The EIS studies were fitted by the (Rs + CPEdl)/(Rct + CPEf/Rf) equivalent circuit model. The kinetic parameters were in favor of a physisorption character of adsorption of HE (AV)/HE (ZM) components onto the mild steel surface. The influence of exposure time on the efficiency of mixture extract was investigated. Scanning electron microscopy (SEM/EDX) analyses confirmed the formation of a protective adsorbed film upon the mild steel surface.