Electrochemical corrosion behavior of gas atomized Al–Ni alloy powders

► Spray-formed Al–Ni alloy powders have cellular microstructures. ► Porosity has no deleterious effect on the electrochemical corrosion behavior. ► Better pitting corrosion resistance is related to a fine powder microstructure. ► A coarse microstructure can be related to better general corrosion resistance. This is a study describing the effects of microstructure features of spray-formed Al–Ni alloy powders on the electrochemical corrosion resistance. Two different spray-formed powders were produced using nitrogen (N2) gas flow (4 and 8bar were used). Electrochemical impedance spectroscopy (EIS), potentiodynamic anodic polarization techniques and an equivalent circuit analysis were used to evaluate the electrochemical behavior in a dilute 0.05M NaCl solution at room temperature. It was found that a N2 gas pressure of 8bar resulted in a microstructure characterized by a high fraction of small powders and fine cell spacings, having improved pitting potential but higher corrosion current density when compared with the corresponding results of a coarser microstructure array obtained under a lower pressure. A favorable effect in terms of current density and oxide protective film formation was shown to be associated with the coarser microstructure, however, its pitting potential was found to be lower than that of the finer microstructure.