Effects of copper addition on the formation of inclusions and the resistance to pitting corrosion of high performance duplex stainless steels

► Copper increased the number and area of numerous oxides and oxy-sulfides. ► Copper increased the activity of chromium. ► Pitting corrosion resistance decreased with an increase in copper content. ► The thermodynamic prediction was in good agreement with the experimental results. To elucidate the effects of copper addition on the formation of inclusions and the resistance to pitting corrosion of alloys, potentiodynamic and potentiostatic polarization tests, a SEM-EDS analysis of inclusions, and thermodynamic calculations of the formation of inclusions were conducted. The addition of copper to the base alloy increased the number and area of numerous (Mn, Cr, (Al), (Fe)) oxides and oxy-sulfides due to an increase in the activity of chromium and resulted in decreased pitting resistance. The thermodynamic prediction of the formation of inclusions was in good agreement with the experimental results.