5-AMINO-1,3,4-THIADIAZOLE-2-THIOL CORROSION CURRENT DENSITY AND ADSORPTION THERMODYNAMICS ON ASTM A-890-1B STAINLESS STEEL IN A 3.5% NaC1 SOLUTION

ABSTRACT 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. Keywords : inhibitor corrosion, duplex stainless steel, potentiodynamic polarization, adsorption isotherm e-mail: mguzman@ucn.cl INTRODUCTION In general, some organic compounds have shown great effectiveness for inhibiting aqueous corrosion in a great variety of metals and alloys