Electrochemical impedance spectroscopy analysis of cold sprayed and arc sprayed aluminium coatings serviced in marine environment

High velocity arc spraying and cold gas dynamic spraying were applied to prepare the aluminium coating, and electrochemical impedance spectroscopy measurement in combination with scanning electron microscopy analysis of corrosion surface and X-ray diffraction results of corrosion product were used to compare the corrosion behaviour of these two coatings. It was found that there was sparse and porous corrosion product covering on the surface of the arc sprayed aluminium coating through which the Cl− can penetrate into the inner coating interface. In contrast, the surface of the cold sprayed aluminium coating after immersion was less porous and tended to seal the pores in the coating. This kind of structure can obstruct the penetration of corrosion medium into the inner coating surface and reduce the corrosion rate to a certain extent. In addition, the diffusion impedance O was introduced in the electrochemical impedance spectroscopy modelling for the purpose of getting good fitting results.