2009 Volume 50 Issue 5 Pages 1214-1218
Selective dissolution of hyper duplex stainless steel was studied by potentiodynamic and potentiostatic test in various concentrations of H2SO4/HCl solutions at various temperatures. There were two peaks in the active-to-passive transition region in potentiodynamic test in 2 M H2SO4 + 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 −270 mV, so that selective dissolution was absent.