The synergistic effect between 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (AMTT) and halides on the corrosion of mild steel in 0.5 M H2SO4 solution at 20 oC is investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Experimental results revealed the significant synergistic action of halides on the protective effect of AMTT. Both protection efficiency (%P) and degree of surface coverage (θ) increase with increasing AMTT concentration, and the effect of halides on the protection efficiency follow the trend: Cl- < Br- < Iindicating that the radii and electronegativity of the halide play a prominent role in the adsorption process. In contrary the synergism followed the reverse order due to the effective inhibition efficiency of iodide. The adsorption of the AMTT accords with the Temkin adsorption isotherm. Some thermodynamic and kinetic parameters have been calculated and discussed.

The synergistic inhibition effect between Cu2+ and 4-amino-5-methyl-4H-1,2,4-triazole-3-thiol (AMTT) on the corrosion behavior of mild steel in 0.5 M H2SO4, both in the absence and presence of chloride ions, has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The ptentiodynamic polarization and EIS results consistently revealed that Cu2+ and AMTT mixture had a synergistic inhibitive effect on the corrosion of mild steel in 0.5 M H2SO4 as a result of the cooperative adsorption of the two species on mild steel. AMTT alone and in combination with Cu2+ and/or chloride were found to obey Temkin adsorption isotherm. Chemical adsorption is proposed based on obtained values of G o ads.

The effect of Nthiazolyl2cyanoacetamide derivatives on the corrosion of aluminum in 0.01N sodium hydroxide has been studied using weightloss and glvanostatic polarization techniques.The inhibition efficiency was found to increase with increasing the concentration of inhibitor and with decreasing tempera ture. The inhibition process was explained in terms of its adsorption on the aluminum surface The adsorption is obeyed Frumkin isotherm. The addition of Ba2+, Sr2+, Ca2+ and Mg2+ ions to Nthiazolyl2cyanoaceta mide derivatives enhanced the inhibition efficiency due to synergistic effect. Polarization data suggested that the additives used as mixed type inhibitors. Some activated thermodynamic parameters were calculated and explained

Kinetic studies on the oxidation of two substituted azinyl formamidines (Azn-Fs), namely N,N-dimethylN’-(pyrimidin-2-yl) formamidine (Pym-F) and N,N-dimethyl-N’-(pyridin-2-yl) formamidine (Py-F), by alkaline permanganate have been performed by spectrophotometry. The spectroscopic and kinetic evidence reveals the formation of 1:1 intermediate complexes between the oxidant and substrates. The influence of pH on the oxidation rates indicated that the reactions are base-catalyzed. The reactions show identical kinetics, being first order each in [MnO4 -]0 and [Azn-F]0, but with a fractional first-order dependence on [OH-]. The effect of temperature on the reaction rate has been studied. Increasing ionic strength has no significant effect on the rate. The final oxidation products of Pym-F and Py-F were identified as 2-aminopyrimidine and 2-aminopyridine, respectively, in addition to dimethyl amine and carbon dioxide. Under comparable experimental conditions, the oxidation rate of Py-F is higher than that of Pym-F. A reaction mechanism adequately describing the observed kinetic behavior is proposed, and the reaction constants involved in the different steps of the mechanism have been evaluated. The activation parameters with respect to the rate-limiting step of the reactions, along with thermodynamic quantities, are presented and discussed.

Kinetic investigations on the oxidation of L-asparagine (Asn) by alkaline permanganate have been carried out spectrophotometrically at a constant ionic strength and temperature. The reaction is first order with respect to [MnO4 -] and less than unit order with respect to both [Asn] and [alkali]. The influence of pH indicated that the oxidation is base catalyzed. The reaction rate was found to increase with increasing ionic strength and temperature. The addition of alkali metal ion catalysts accelerates the oxidation rate. The proposed reaction mechanism involves the formation of a 1:1 intermediate complex between L-asparagine and an alkali-permanganate species in a pre-equilibrium step, which was confirmed by both spectral and kinetic evidence. The complex decomposes slowly in a rate determining step, resulting in the formation of a free radical. The latter reacts again with another alkali-permanganate species in a subsequent fast step to yield the final reaction products which were identified as aldehyde (a-formyl acetamide), ammonia, manganate(VI) and carbon dioxide. The appropriate rate laws are deduced. The reaction constants involved in the mechanism were evaluated. The activation and thermodynamic parameters were determined and discussed.

The behavior of some biopolymeric metal-alginate hydrogel spheres of ionotropic nature in aqueous solutions has been investigated. Cross-linked ionotropic biopolymeric hydrogels such as MnII , CoII , NiII , CaII, SrII and SeIV-alginate showed an appreciable tendency for swelling in water, whereas that of CuII-, SnII-, BaII, PbII, AlIII, CrIII and FeIII-alginates showed a remarkable tendency for shrinking. The swelling processes were accompanied by an increase in volume and transparency; while a decrease in the pore size with a simultaneous increase in hardness was followed the shrinking processes. Drying of these metal-alginate ionotropic hydrogel spheres indicated that the water content exceeds 90% of the gel weights. The kinetics of swelling and shrinking processes have been studied. The factors which affect that behavior were examined and discussed in terms of the mechanical stability and the changes in some rheological properties of these ionotropic hydrogel spheres.

:The inhibitive effects of some antibacterial cephalosporin (cefotaxime, cefalexin, cefradine and cefazolin) on the corrosion of iron in 0.5 M H2SO4 solution was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Results showed that the inhibition efficiency increased with an increase in concentration of inhibitor. Potentiodynamic studies proved that the inhibitors act as mixed type .The inhibitors are adsorbed on the iron surface according to Langmuir isotherm equation. All impedance spectra in EIS tests exhibit one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. Inhibition efficiencies obtained from Tafel polarization, charge transfer resistance (Rct) is consistent.

The change in rheological and mechanical properties for some ionotropic cross-linked metal-alginate hydrogel complexes in particularly copper-alginate membranes in the presence of some organic solvents (benzene, toluene, xylene, carbon tetrachloride, acetone, chloroform, dichloroethane, isobutyl alcohol and ethyl alcohol) or buffer solutions (acetates, borates and universal buffers) have been investigated. The experimental results showed a remarkable tendency of the studied hydrogels for shrinking in polar solvents, whereas no influence was observed for the hydrogels in non-polar solvents. On the other hand, the gels were found to swell or shrink in the buffer solutions depending on the pH of the buffer used. The swelling extent for hydrogel spheres was found to decrease in the order Cu > Ba ≈ Ca > Zn > Pb-alginates in universal buffers of pH = 5.33. The factors affected this behavior have been examined and discussed.

The kinetics of oxidation of kappa-carrageenan (KCAR) as a sulfated polysaccharide by cerium(IV) in aqueous perchlorate solutions at a constant ionic strength of 2.0 mol dm−3 have been investigated, spectrophotometically. The results showed a first-order dependence in [CeIV] and fractional-first-order kinetics in carrageenan concentration. A kinetic evidence for the formation of 1:1 complex has been revealed. The hydrogen ion dependence of the reaction rate indicated that the oxidation process is acid catalyzed. The oxidation product was identified by the spectral data and elemental analysis. The activation and thermodynamic parameters have been evaluated and a relevant reaction mechanism is suggested and discussed.