Corrosion Behavior of FeNiCrMoSiC Laser Cladding Coatings with Different Addition of Ni Content in Acidic Environment

Three FeNiCrMoSiC laser cladding coatings with different Ni content were deposited on AISI 4130 substrate. The electrochemical corrosion behavior of three FeNiCrMoSiC coatings in 0.5 mol/L HCl solution was investigated by the polarization curve and electrochemical impedance spectroscopy measurement. X-ray photoelectron spectroscopy and Mott-Schottky tests were employed to evaluate the passive film on the coating surface to investigate the passivation stability mechanism of the coating in hydrochloric acid. Potentiodynamic polarization results show that the FeNiCrMoSiC coatings shown superior corrosion resistance than the AISI 4130 substrate, demonstrated by lower corrosion current density and higher corrosion potential. With the increase of Ni concentration, the content of austenite γ -Fe phase increased, whilst the volume of ferrite α -Fe phase decreased, and the corrosion resistance of FeNiCrMoSiC coatings also increased. The main reason for the excellent corrosion resistance of the coating is the barrier effect of bilayer oxide passive film, which is difficult to dissolve in acid and can effectively slow down the penetration of corrosive ions in hydrochloric acid solution on the coating surface.