Hot corrosion behavior at 650 °C of Ni–Al composite coating prepared by electroplating nickel and embedded aluminizing technology

Abstract

The hot corrosion performance of the Ni–Al composite coating prepared by electroplating nickel and powder embedding aluminizing technology in a mixed salt of Na2SO4:NaCl (3:1 and 3:2, mass ratio) at 650 °C was tested. The results show that the hot corrosion of the coating has an incubation period of 190 h and 96 h for the corrosive agent having 3:1 and 3:2, respectively. The increase of NaCl content in the corrosive agent can accelerate the corrosion process. Only oxidation occurs in the first 48 h of the hot corrosion of the coating, resulting in the formation of Al2O3 and a small amount of NiO on the surface of the coating. When the corrosion time ups to 504 h, the coating has different degrees of internal oxidation and internal sulfidation. The corrosion products include mainly NiO, Ni3S2, Fe2O3, Fe3O4 and Ni(Cr, Fe)2O4, in which Cr2S3 produced in the inner layer having a dark brown color is loose and peeled off in layers.