Pitting Corrosion Resistance of Ta-Bearing Duplex Stainless Steel

Abstract

The effect of Ta addition on the pitting corrosion resistance of duplex stainless steels was investigated in both cases without and with deoxidization/desulfurization by addition of Al and Ca. The pitting corrosion resistance was improved by addition of Ta with two proposed mechanisms. For steels without Al and Ca, the MnS inclusions which act as initiation sites of the pitting corrosion are modified to the electrochemically-stable (Ta,Mn) oxysulfides. For steels with Al and Ca, the pitting initiation sites (CaS and (Al,Ca) oxides) are coated with the stable Ta-containing nitrides resulting in the suppression of pitting corrosion propagation.