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In the present work, further analysis of complex conductivity was carried out. In particular, the first derivative of the ac conductivity of polysaccharide solutions provides a good differentiation of the different contributions of the conductivity. Moreover, this procedure allowed us to prove and confirm the validity of the equivalent circuit. In addition, a new electrical circuit was proposed to fit the complex conductivity. The main aim is focused on the analysis of the change in the electrical properties involved in the Cole–Cole relaxation process at medium and high frequencies, which in turn allowed us to extract crucial parameters such as ionic strength, dc conductivity, and relaxation time. It is found that their evolutions as a function of concentration revealed a clear transition at 5% (w/v), suggesting the transition from the dilute to the semi-dilute domain due to the cross-linking between polyvalent counterions and chains molecular. [ABSTRACT FROM AUTHOR]

The extract of Origanum elongatum Emb. and Maire (OEE) was used as a corrosion inhibitor for C38 steel in 1N HCl medium, the inhibitory effect was studied by different techniques, weight loss and electrochemical measurements. Weight loss measurements indicate a maximum efficiency of 77.50% at a concentration of 1 g/L at 298 K. The potentiodynamic polarization shows that OEE is a mixed type of inhibitor. Electrical impedance spectroscopy measurements show an increase in charge transfer resistance accompanied by a decrease in double layer capacitance, suggesting that the OEE extract acts by adsorption on the metal surface, the decrease in the double layer is always related to the decrease in the dielectric constant and/or the increase in the thickness of the electrical double layer. Adsorption of active OEE species in 1N HCl on C38 steel follows Langmuir isotherm. A fractionation was performed on the OEE, which resulted in three different fractions. These fractions and the OEE were analysed by infrared spectroscopy, the inhibitory efficiencies of the fractions were tested by the weight loss measurements. [ABSTRACT FROM AUTHOR]