Passivation behavior and surface chemistry of 2507 super duplex stainless steel in artificial seawater: Influence of dissolved oxygen and pH

Passivation and film chemistry of 2507 super duplex stainless steel in modified artificial seawater (ASW) are investigated. Removal of dissolved oxygen decreases the electric field strength and point defect diffusivity of the passive film. Passive current density in acidified ASW is higher than that in aerated ASW due to increased potential drop across film/solution interface, donor density and point defect diffusivity. The content of oxidized Cr, Fe(II) and hydroxides increases and film thickness reduces with acidification. In acidified ASW, passive film become denser from pre-passivation to passivation region and pores form accompanied with the increase of oxidized Fe after transpassivation.