Effect of La2O3 on corrosion resistance of laser clad ferrite-based alloy coatings

The ferrite-based alloy powders with different contents of La2O3 were laser clad on a steel substrate. The microstructural features and phase structure of these coatings were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The results showed that the microstructure of the coatings with La2O3 was refined and purified. The main phase of the coatings was γ (Fe, Ni). Moreover, the electrochemical properties of the coatings were investigated by anodic polarization curves and electrochemical impedance spectroscopy (EIS). Anodic polarization results indicated that both polarizing voltage and polarization current density were reduced with the addition of La2O3. EIS results showed that, with the increment of La2O3, the inductive arcs shrunk and capacitive arcs expanded. The inductive arc at low frequency was disappeared and changed to capacitive arc thoroughly when the content of La2O3 reached 1.2 wt.%. The corrosion weight loss experiment results showed that the corrosion rate was lower and the corrosion attack was lighter in the coatings with La2O3 than that without La2O3, resulting in a substantial improvement of the corrosion resistance.