Effect of solution treatment on structure of oxide scales for 2205 duplex stainless steel

The oxide scales of 2205 duplex stainless steel plates were studied at hot- rolled state and solid- solution state by SEM, XRD and EDS. The oxide scales on the surface of 2205 duplex stainless steel are composed of a variety of oxides, such as Fe2O3, Cr2O3, FeO??Cr2O3 and NiO??Fe2O3 with spinel structure. After the solution treatment, the oxide scales on the surface changed, in the meantime, the oxidation occurred in the stainless steel substrate. The content of Cr, Ni, Mo increased in the oxides contacting with the substrate, in addition, the distribution of Cr and Ni was more evenly in the oxide scales. The content of Si, Mo increased significantly in the contacting part with the substrate. The surface of the steel plate was formed by a certain outside- in hierarchical oxide phase of Fe, Mo, Ni, Cr and Si. The stability and complexity of the oxide film increased, so it was more difficult to be removed by acid pickling.