Mixed potential model for passivity characters of hyper-duplex stainless steel 2707 in ammonium carbonate solution containing chloride

A mixed potential model (MPM) comprising the Point Defect Model (PDM) and the Generalized Butler Volmer Equation (GBVE) was successfully developed to study the passivity of HDSS 2707. The results show that the dominant point defect within the passive film is the Min+, thereby rendering n-type semiconductor behavior of the barrier layer. The anodic current is independent of the film formation potential whereas it increases with increasing temperature and follows the Arrhenius law. The partial cathodic current of hydrogen reaction is affected by the applied voltage. The anodizing constant of the passive film is calculated to be 2.91 nm/V.