Portugaliae
Electrochimica Acta

The inhibition efficiency (IE) of an aqueous extract of beet root (BR) in controlling corrosion of carbon steel in well water in the absence and presence of Zn2+ has been evaluated by mass loss method. The formulation consisting of 4 mL of BR extract and 50 ppm Zn2+ offers 98% inhibition efficiency to carbon steel immersed in well water. A synergistic effect exists between BR extract and Zn2+. Addition of N-Cetyl-N,N,N – trimethylammonium bromide (CTAB) does not change the excellent inhibition efficiency of the BR – Zn2+ system. The BR – Zn2+ system shows excellent IE up to 7 days. Polarization study reveals that this formulation controls the cathodic reaction predominantly. AC impedance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Fe2+ - betanin complex and Zn(OH)2. The film is found to be UV - fluorescent.

The corrosion inhibition of mild steel in H2SO4 in the presence of methocarbamol was studied using thermometric and gasometric (hydrogen evolution) methods. The study revealed that the corrosion rate increases with temperature, time and concentration of H2SO4. Addition of methocarbamol to the corrodent solution lowered the corrosion rate of mild steel. Inhibition efficiency (%I) of methocarbamol was found to increase with concentration and decreased with temperature. Adsorption of methocarbamol molecule on mild steel surface was found to obey the Langmuir adsorption isotherm. The phenomenon of physical adsorption is proposed from the obtained thermodynamic parameters.

The inhibition efficiency (IE) of malonic acid (MA)-Zn2+ system in controlling corrosion of carbon steel immersed in well water has been evaluated by weight-loss method. The formulation consisting of 50 ppm of MA and 50 ppm of Zn2+ has 85% IE. The influence of N-cetyl-N,N,N-trimethylammonium bromide (CTAB) and N-cetyl pyridinium chloride (CPC) on the IE of the MA- Zn2+ system has been studied. At lower pH value (pH=6) IE decreases and in alkaline medium (pH=8) IE increases. Polarization study reveals that MA-Zn2+ system functions as a mixed inhibitor. AC impedance spectra reveal that a protective film is formed on the metal surface. FTIR spectra reveal that the protective film consists of Fe2+-MA complex and Zn(OH)2.

Inhibitive and adsorption properties of ethanol extract of vernonia amygdalina for the corrosion of mild steel were studied using weight loss, thermometric, gasometric and IR methods of monitoring corrosion. The results revealed that ethanol extract of Vernonia amygdalina inhibited the corrosion of mild steel. The inhibition efficiency of the extract increased as the concentration of the extract increases. The inhibitor was found to function by being adsorbed on the surface of mild steel. The adsorption of the inhibitor followed the Langmuir adsorption isotherm. IR spectra of the corrosion product (without inhibitor), the extract and the corrosion product (with the inhibitor) confirmed that ethanol extract of vernonia amygdalina is an adsorption inhibitor. Phytochemical studies also revealed that ethanol vernonia amygdalina contains tannin, saponnins, flavanoid and anthraquinone, all of them contributing to the corrosion inhibition. Physical adsorption mechanism has been proposed from the values of some of the thermodynamic parameters obtained.

The aim of this research is to obtain electrodeposits of copper-tin over mild steel substrate. The plating parameters were studied and a model is developed using Artificial Neural Networks (ANN). The electrodeposition of copper-tin was carried out from an alkaline cyanide bath. Copper content of coatings in alloy deposition was determined by using X-ray fluorescence spectroscopy. The results were used to create a model for the plating characteristics and also for studies using ANN. The ANN model is compared with the conventional mathematical regression model for analysis.

Inhibition of the corrosion of zinc in various concentrations (0.01 to 0.05 M) of H2SO4 was studied using weight loss and hydrogen evolution methods of monitoring corrosion. The results revealed that various concentrations of azithromycin (0.0001 to 0.0005 M) inhibited the corrosion of zinc in H2SO4 at different temperatures (303 to 333 K). The concentration of H2SO4 did not exert significant impact on the inhibition efficiency of azithromycin, but inhibition efficiencies were found to decrease with increase in the concentration of the inhibitor. Values of inhibition efficiency obtained from the weight loss measurements correlated strongly with those obtained from the hydrogen evolution measurements. The activation energies for the corrosion of zinc inhibited by azithromycin were higher than the values obtained for the blank. Thermodynamic data revealed that the adsorption of azithromycin on the surface of zinc was endothermic (values of enthalpies of adsorption were positive), spontaneous (values of free energies of adsorption were negative) and was consistent with the adsorption model of Langmuir.