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