Corrosion behavior of electroless nickel-coated AISI 304 stainless steel enhanced by titanium ion implantation

Metal plasma ion implantation has been successfully developed to improve the wear, corrosion, and physical properties of various engineering materials. In this study, Ti ions were implanted into electroless nickel coating at 100 keV and 5×1016–3×1017 ions/cm2 using a metal plasma ion implantation apparatus. Within the implanted region, the hardness of the electroless nickel coating is increased from 14 to 18–22 GPa by Ti ion implantation at doses of 1×1017–3×1017 ions/cm2. The electrochemical behavior of the Ti-implanted electroless nickel in a 3.5 wt.% NaCl solution was investigated by the potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The corrosion resistance of Ti-implanted electroless nickel was improved by the formation of chemically inert titanium oxides and Ti–Ni alloys in the ion-implanted layer, which leads to the increase of polarization resistances in the EIS analysis. At the dose of 3×1017 ions/cm2, the Ti-implanted electroless nickel possesses the best corrosion resistance due to the highest polarization resistance (3.05×105 Ω/cm2) and the lowest capacitance (1.5×10−5 F/cm2). Results of this study demonstrate the potential of metal plasma ion implantation in improving the corrosion resistance of the electroless nickel with enhanced mechanical properties.