Effect of Chemical Composition on Salt Spray Corrosion Performance of Laser Thermal Sprayed Amorphous Al–Ni Coatings

Abstract

Amorphous Al–Ni coatings with the different Al/Ni mass ratios (MRs) were fabricated on S355 steel using a laser thermal spraying. The surface morphologies, chemical composition, and phases of obtained amorphous Al–Ni coatings were analyzed using a field emission scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer, respectively. The effect of chemical composition on the salt spray corrosion (SSC) performance of Al–Ni coating was investigated using a SSC test box. The results show that the Al–Ni coatings consist of Al–Fe and Al–Ni amorphous phases, and the stress corrosion and grain boundary segregation of the Al–Ni coating lead to cracking on the coating surfaces. The corrosion products on the Al–Ni coatings fabricated with the Al/Ni MRs of 3:1 and 4:1 are Ni–Mn–Al, Al2O3, NaFeCl4, γ–FeO(OH), and α–FeO(OH) phases, in which the dense Al2O3 film hinders the corrosion anions into the substrate, and the SSC resistance of the Al–Ni coating fabricated with the Al/Ni MR of 4:1 is the best among the three kinds of coatings.