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The electrical conductivities of Ag (I), Ca (II), Sr (II), Cu (II), Zn (II), Cd (II) and Pb (II)alginate complexes in the form of circular discs have been investigated as a function of a wide range of temperatures. At lower temperatures, the Arrhenius plot of In 6 vs 1/T showed that the electrical conductivity for the silver-alginate complex was gradually increased until it reached a maximum and then began to decrease with temperature, whereas no change in the electrical conductivity was observed with respect to the divalent metal-alginate complexes. Again, at higher temperatures, 6 values increased continuously with temperature for both monoand divalent metal-alginate complexes. X-ray diffraction patterns showed that all these alginate complexes are amorphous in nature. IR absorption spectra indicated the presence of chelated metal ions in the chains of alginate macromolecules. The activation energies have been calculated and tentative conduction mechanisms in good agreement with the experimental results are suggested.

The kinetics of decomposition of an [Pect·Mn VI O 4 2− ] intermediate complex have been investigated spectrophotometrically at various temperatures of 15-30 • C and a constant ionic strength of 0.1 mol dm −3 . The decomposition reaction was found to be first-order in the intermediate concentration. The results showed that the rate of reaction was basecatalyzed. The kinetic parameters have been evaluated and found to be S = = −190.06 ± 9.84 J mol −1 K −1 , H = = 19.75 ± 0.57 kJ mol −1 , and G = = 76.39 ± 3.50 kJ mol −1 , respectively. A reaction mechanism consistent with the results is discussed.

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ABSTRACT:The effects of poly(vinyl alcohol) (PVA), poly(acrylic acid) (PAA), sodium polyacrylate (NaPA), poly-(ethylene glycol) (PEG), pectin (P), and carboxymethyl cellulose (CMC) on the corrosion of cadmium in a 0.5M hydrochloric acid (HCl) solution were studied with both electrochemical impedance spectroscopy and Tafel plot techniques. Measurements were carried out at cathodic, open-circuit, and anodic potentials. All the investigated polymers had inhibitory effects on both the cathodic (except for NaPA, P, and CMC) and anodic processes, with a predominant anodic inhibiting action. However, NaPA, P, and CMC exhibited a slight cathodic inhibiting action only at higher polymer concentrations. This behavior may be attributed to the very weak adsorbability of the polymers on the cathodic sites. Because PVA and PEG had hydroxy groups, there could be bridging between the polymer and the surface, resulting in an inhibiting effect in the HCl solution. However, PVA had much greater adsorbability on the surface than PEG at the anodic potential. The adsorption of most of the polymers obeyed a Temkin adsorption isotherm, and this indicated indicating that the main process of inhibition was adsorption.

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