Electrochemical removal of sulfide ions was achieved in salt water using graphite anodes in an autoclave under high temperatures and pressures, simulating geothermal fluids. The reaction products were characterized using microscopy and X-ray photoelectron spectroscopy (XPS). At low temperatures the reaction rate is quite small. It decreases rapidly with time down to a negligibly small value, which increases only slightly with temperature. The reaction produces elemental sulfur, which was seen under the microscope and identified using XPS. It passivates the electrode and hence diminishes its activity. Above about 115°C, much higher removal rates can be sustained for much longer times, while the increase of temperature has a much stronger effect on the reaction rate. Under this condition, elemental sulfur was no longer detected among the reaction products, while the electrode retained its activity for continuous operation. The XPS spectra at high temperatures reveal the presence of oxygen bearing sulfur species, such as sulfates. The melting of sulfur (at 115°C) has a much stronger effect on the efficiency of the process than the transition of orthorhombic to monoclinic sulfur (at 95°C). A Clausius-Clapeyron's analysis reveals that the melting point of sulfur inside the autoclave is nearly equal to its normal melting point.

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A new method was proposed for the application of azole corrosion inhibitors on the surface of copper. This method depends on the vacuum pyrolysis of the inhibitor in the presence of copper specimens. Three azole inhibitors namely; benzotriazole (Azole (1) (2)) and N-[Benzotriazol-1-yl-(4-methoxy-phenyl)-methylene]-N-phenyl-hydrazine (Azole (3)) were tested. After pyrolysis copper samples were electrochemically tested in sulfide polluted salt water and compared to the behavior of copper tested in the sulfide polluted salt water containing dissolved benzotriazole. Results showed that copper specimens treated in the presence of Azoles (2) and (3) exhibit excellent corrosion resistance. Those samples could resist the poisoning effect of sulfide ions. Azole (1) shows good resistance at low sulfide concentration and failed at the high concentration. Surface investigation support the results of electrochemical tests.

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This paper treats the electrochemical oxidation of sulfide ions on platinum using cyclic voltametry.  An electrolyte of 3.5% NaCl containing sulfide ions was used as the testing medium.  The effects of scan rate, concentration of sulfide ions and temperature on the cyclic voltamograms were investigated.

Cyclic voltamograms show small currents in the absence of sulfide ions.  In the presence of sulfide ions, the magnitude of the anodic currents in the forward sweep is much more than these in the reverse sweep.  Cyclic voltamograms show three features appear in the forward sweep at potentials of  -0.1, 0.475 and 1.0 V vs Ag/AgCl, respectively.  Peaks currents are increased upon the increase of either the scan rate or temperature.  These peaks are explained to show the possible formed species and the possible electrochemical oxidation reactions at the electrode surface. 

The kinetics of interaction of benzotriazole (C 6 H 5 N 3 , BTAH) with the surface of copper in salt water were studied using an electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy (XPS). Upon injecting BTAH into the electrolyte, three regions appear in the time response of the microbalance. Region I (at short time of few minutes), exhibits rapid linear growth of mass with time, which is attributed to the formation of a protective Cu(I)BTA complex. Region II reveals attachment of BTAH at a slower rate onto the inner Cu(I)BTA complex. Region III is a plateau indicating that the BTAH film attains an equilibrium mass and thickness, which increase with the concentration of BTAH. The intensity of the N1s peak in the XPS spectra increases with the time of immersion, indicating more BTAH on the surface. The results suggest a duplex inhibitor film composed of an inner thin layer of Cu(I)BTA and an outer layer of physically adsorbed BTAH which increases in thickness with time and BTAH concentration. They also offer an explanation for the much documented findings of simultaneous increase of the polarization resistance and decrease of double layer capacity with inhibitor concentration and time of immersion.