Abstract

Many sulfide minerals immersed in conductive aqueous solutions, like chalcopyrite, galena, pyrite, bornite, have sufficient electrical conductivity to allow electrochemical interaction with surrounding phases. A particular system of industrial interest is the pulp solution containing suspended sulfide mineral, where the interaction between mineral-steel in contact with electrolyte solutions will lead to form an electrochemical galvanic couple promoting an accelerated corrosion of the main steel components of mining plants causing significant costs in repair and maintenance. In this context, the deployment of preventive measures to minimize the galvanic corrosion requires an accurate knowledge of the corrosion behavior under varied conditions. The objective of this work was to study the galvanic corrosion of carbon steel-pyrite couple immersed in NaCl solutions by applying of the mixed potential theory and the superimposition model. Galvanic corrosion parameters were archived for aerated solutions with different chloride concentrations under a constraint of net zero current density, where the anodic branch of carbon steel is intercepted with the cathodic branch of pyrite mineral. A three electrodes cell with a rotating disc working electrode was used to assess the electrochemical behavior of the pyrite mineral and the carbon steel. In order to eliminate the interference from minor common constituents of natural pyrite mineral, the electrochemical test were performed using pure pyrite as a working rotating disc electrode. Similarly the carbon steel electrodes were made from commercial bars. The following main results can be drawn: A).- The galvanic corrosion can be reasonably predicted by superimposition of the individual galvanic couple mineral-electrolyte and steel-electrolyte. B).- Both anodic and cathodic reactions were highly influenced by the increase in the chloride concentration. C).-The reduction of the galvanic impact with the chloride concentration is explained principally by changes on the cathodic oxygen reduction reaction.