Dissolution characteristics of duplex stainless steels in acidic environments

To determine differences in the dissolution rates of the austenitic and ferritic phases in duplex stainless steels an in situ investigation was carried out in acidic solutions of 2 M H₂SO₄ with 2 M HCl. The current density distribution over the active surface was measured using a scanning vibrating electrode. The study demonstrated that this technique could measure differences 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 current maxima. In addition, transients in the dissolution behavior of the two phases were observed at different potentials using optical microscopy. Electron microscopy showed aluminum and silicon enrichment at the austenitic phase after dissolution.