Effect of Ultrasonic Treatment on the Structure and Corrosion of Al₂O₃/Ni-W-Fe-P Coating for Car

The surfaces of Q195 steel,an advanced material in chemical/auto/aerospace industries,were modified with Al₂O₃-doped,Ni-based W-Fe-P coatings deposited by electroless plating.The influence of the ultrasonic churning and addition of Al₂O₃powderto the chemical solutions on the microstructures and corrosion/erosion behavior was investigated with X-ray diffraction,scanning electron microscopy and energy dispersive spectroscopy.The results show that the Al₂O₃-adition and ultrasonic churning had a major impact.For instance,the amorphous Al₂O₃-doped Ni-W-Fe-P coatings,comprising randomly distributed Al₂O₃ spheres,significantly improved the corrosion/erosion resistance,increased the compactness/hardness/interfacial-adhesion and decreased the porosity and surface roughness.Moreover,ultrasonic churning outperforms mechanical churning of chemical solutions because of stronger interfacial adhesion,faster surface reaction and better protection of Q195 substrate in electroless plating.