Effects of laser power on immersion corrosion and electrochemical corrosion performances of laser thermal sprayed amorphous AlFeSi coatings

Amorphous AlFeSi coatings were fabricated on S355 structural steel using a laser thermal spraying (LTS). The surface and cross–section morphologies, chemical composition, phases and chemical valences of obtained coatings fabricated at the laser power of 1400, 1600 and 1800 W were analyzed using a scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X–ray diffractometer (XRD), and X–ray photoelectron spectrometer (XPS), respectively. The immersion corrosion and electrochemical corrosion performances of AlFeSi coatings fabricated at the different laser power were investigated using a salt spray corrosion (SSC) chamber and electrochemical workstation. The results show that the laser thermal sprayed AlFeSi coatings are primarily composed of the crystalline and amorphous mixed phases of AlFe, AlCrFe₂, AlFe₃ and Al_0.7Fe₃Si_0.3. The Al, Fe and Si of AlFeSi coating are diffused into the substrate at the coating–substrate interface, forming a metallurgical bonding. In the immersion corrosion test, the formation of occluded cell produces the acidification in the porosity, which gradually expands to corrosion pits and cracks, accelerating the corrosion process. The corrosion current densities (I_corr) of AlFeSi coatings at the laser power of 1400, 1600 and 1800 W are 9.989 × 10⁻⁶, 8.898 × 10⁻⁶, and 6.542 × 10⁻⁶ A·cm⁻², respectively, lower than 1.617 × 10⁻⁵ of substrate, the electrochemical corrosion resistance of AlFeSi coating increases with the increase of laser power.