Investigating corrosion mechanisms and the electrochemical performance of ferrosilicon for dense medium separation operations in Botswana

Abstract

Ferrosilicon (FeSi) is widely used in dense medium separation (DMS) processes for mineral beneficiation, however, its degradation due to corrosion presents significant operational challenges. Despite its industrial importance, limited research has addressed the electrochemical behavior of FeSi under the conditions specific to Botswana’s mining operations. This study investigates the corrosion mechanisms and electrochemical performance of three milled FeSi grades (100D, 150D, and 270D) using open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS), and surface characterization techniques (SEM-EDS, XRD, Raman Spectroscopy, and particle size distribution). The results reveal that 270D demonstrated the best overall corrosion resistance, exhibiting the highest charge transfer resistance ( R ct = 139,370 Ω·cm 2 ), followed by 100D ( R ct = 139,700 Ω·cm 2 ), and lastly 150D ( R ct = 51,020 Ω·cm 2 ), which consistently exhibited the poorest corrosion resistance across all techniques. 150D showed the highest corrosion current density (I corr = 1.57 × 10 −3 A/cm 2 , while 100D; I corr = 1.94 × 10 −4 A/cm 2 , and 270D; I corr = 1.50 × 10 −4 A/cm 2 ) and the most negative corrosion potential (E corr ), indicating poorest corrosion resistance. OCP measurement confirmed that 150D exhibited more frequent electrochemical fluctuations, indicative of lower surface stability. Particle size distribution shifted from unimodal to bimodal in all corroded samples, suggesting corrosion-induced particle fragmentation and agglomeration. These finding contribute to material selection and process optimization for more cost-effective and sustainable DMS operations in Botswana.