Theoretical and experimental studies of passivity breakdown of Aermet 100 ultra‐high stainless steel in chloride ion medium

Abstract Passivity breakdown and pitting behavior in the presence of aggressive Cl − on ultra‐high strength steel Aermet 100, commonly used for landing gear, has been studied, the data are explained in view of the point defect model (PDM). Cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and X‐ray photoelectron spectroscopy (XPS) were examined to observe corrosion progress and corrosion products in the salt spray tests at 4, 8, 12, 16, and 20 days intervals. The breakdown behavior was studied using CPP, whereas scanning electron microscopy (SEM) and digital confocal microscopy were used to explore the micromorphology and depth distribution of pits. The cumulative distribution basically satisfies a normal probabilistic distribution at the different concentrations of chloride and pH, which is consistent with PDM assuming a near‐normal distribution of potential breakdown sites regarding to the cation vacancy diffusivity.