In this study, the effect of ultrafine-grained (UFG) structure on the passivation behavior of 1050 aluminum alloy in a borate buffer solution (pH=5.5) has been investigated. UFG sample was fabricated by accumulative roll bonding (ARB) technique as a severe plastic deformation process for the industrial production of UFG and nano structure sheets with excellent mechanical properties. X-ray diffraction pattern (XRD) and Atomic force microscopy (AFM) were used for determination of microstructure and grain size refining after 7 cycles of ARB process. Passivation behaviors of annealed sample compared to 3 and 7 cycles number of ARBed samples by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) after 2 h immersion in test solution. The potentiodynamic polarization plots revealed that the higher number of cycles for samples processed with the ARB method rather than annealed sample yield to lower corrosion and passive current densities and more noble corrosion potential values. Moreover, electrochemical impedance spectroscopy (EIS) measurements showed that increasing the number of ARB cycles offer better conditions for forming the passive film. Compared to annealed sample, it was found that passivation behavior of the ARBed samples improved and their grain size decreased.
