Composition Distribution and Electrochemical Behavior of an Ni2Al3 Coating on Q235 Steel

An Ni2Al3 coating was prepared via the electrodeposition of nickel followed by pack aluminization. Polarization curve and electrochemical impedance spectroscopy were performed to study the room temperature corrosion behavior of the coating in a 3.5 wt. % NaCl solution. The long-term impedance of the coating was also investigated after immersion for 30 days. Results show that the Ni2Al3 coating possessed lower corrosion current density (Icorr) and higher polarization resistance (Rp) than the substrate in the solution. The Bode plots of the coating showed two time constants after the long-term immersion. Pitting corrosion was found on the coating surface.