Dissolution characteristics of duplex stainless steels in acidic environments

To determine differences in the dissolution rates of the austenitic and fer ritic phases in duplex stainless steels an in situ investigation was carrie d out in acidic solutions of 2 M H2SO4 with 2 M HCl. The current density di stribution over the active surface was measured using a scanning vibrating electrode. The study demonstrated that this technique could measure differe nces in the dissolution rates of the austenitic and ferritic phases. These observations were validated using model calculations. The dissolution rates for the two phases peak at different potentials resulting in multiple curr ent maxima. In addition, transients in the dissolution behavior of the two phases were observed at different potentials using optical microscopy. Elec tron microscopy showed aluminum and silicon enrichment at the austenitic ph ase after dissolution. (C) 1998 Elsevier Science Ltd. All rights reserved.