Selective Dissolution Characteristics of 26Cr-7Ni-2.5Mo-3W Duplex Stainless Steel in H<SUB>2</SUB>SO<SUB>4</SUB>/HCl Mixed Solution

Abstract

Selective dissolution of hyper duplex stainless steel was studied by potentiodynamic and potentiostatic test in various concentrations of H 2 SO 4 /HCl solutions at various temperatures. There were two peaks in the active-to-passive transition region in potentiodynamic test in 2 M H 2 SO 4 + 0.5 M HCl solution at 60°C. In potentiostatic tests, the curve at ―340 mV showed stable current density. As the potential increased, the current density increased and at above ―310 mV potential, there was a much longer initial period of nonsteady current value. As the potential reached at ―280 mV, the current density started to be stabilized and the current density was completely stabilized at ―250 mV. It was found that a preferential dissolution of ferrite phase occurred at ―330 mV and with the increase of potential, austenite phase was corroded at a high rate. On the other hand, both two phases were passivated at the potential above ―270mV, so that selective dissolution was absent.