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The copolymerization of 1,3,4-thiadiazole-2,5-dithiol (bismuthiol) with 1+, 2+, and 3+ valent metals is reported. Polymerization conditions were mimicked by means of Job's technique of solutions mixing. The polymers in aqueous solution do not conduct electricity, but electrolytes are formed in proportion to polymer formation and the pH changes. The metal concentration in solutions confirms the metal-ligand stoichiometry. The UV absorption of the ligand (at 320 nm) decreases and light scattering by polymer (at 380 nm) increases with polymer formation. The stoichiometry of polymers (obtained from the conductivity inflection point and metal analysis) is as follows, Mt2+: bismuthiolate = 1 : 1; A13+ : bismuthiolate = 2 : 3 and Ag+ : bismuthiolate = 2 : 1. Equations describing polymer formation on the basis of the solution conductivities are presented, and a model of polymer formation is proposed. It is concluded that 2+ valent metals form linear polymers but A13+ forms branched polymers.

Using the electrochemical linear polarization resistance technique, 5-amino-1,3,4-thiadiazole-2-thiol corrosion current density on ASTM A-890-1B steel is determined in a 3.5% NaCl solution at different temperatures. The corrosion inhibition process is mixed. Apparent activation energy is calculated, being the one with inhibitor slightly greater than that without it. Adsorption matches Damaskin-Parsons isotherm, showing that molecules adsorbed by the metal surface reject each other. Three water molecules on the metal surface are replaced by one inhibitor molecule. This is demonstrated by calculating the surface these molecules project. Normal thermodynamic adsorption parameters are calculated, showing that the process is spontaneous and exothermic. Inhibitor adsorption on the metal surface is a chemical adsorption.

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