Thermodynamics of inclusion formation and its influence on the corrosion behavior of Cu bearing duplex stainless steels

To elucidate the thermodynamics of inclusion formation and its influence on the corrosion behavior of Cu bearing duplex stainless steels, potentiodynamic and potentiostatic polarization tests, a SEM-EDS analysis of inclusions, and thermodynamic calculations of the formation of inclusions were carried out. While the resistance to general corrosion of the noble copper contained alloy-1.5Cu in a deaerated 2 M H2SO4 was higher than that of the alloy-BASE, the resistance to pitting corrosion of copper contained alloy-1.5Cu in a deaerated 0.5 N HCl + 1 N NaCl and 30 mass% NaCl was lower than that of the alloy-BASE due to an increase of interface areas between inclusions and matrix acting as preferential pit initiation sites. The thermodynamic calculation for the formation of Cr-containing oxide inclusions was in good agreement with the experimental results. (author)