► The corrosion behaviour of AISI 316L and 2205 DSS in orthodontics. ► The increased passive range for DSS 2205 compared to AISI 316L in artificial saliva. ► Higher R p values of DSS compared to AISI 316L in artificial saliva. ► The main constituent of the passive layers on DSS at the OCP in saliva was Cr-oxide. ► DSS 2205 is suitable for orthodontic applications in artificial saliva. The evolution of the passive films on 2205 duplex stainless steel (2205 DSS) and AISI 316L stainless steel in artificial saliva, and with the addition of fluoride, was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements. The extent of the passive range increased for the 2205 DSS compared to the AISI 316L in both solutions. The formation of the passive film was studied by EIS at the open-circuit potential (OCP). The passive layers were studied at the OCP by X-ray photoelectron spectroscopy (XPS). The passive films on both materials predominantly contained Cr-oxides, whereas the Fe species were markedly depleted.