Effect of plasma nitriding of electroplated chromium coatings on the corrosion protection C45 mild steel

Plasma nitriding is a promising posttreatment technique to create a nitride layer on electroplated chromium coatings for improving their corrosion resistance. In the present study, the effects of plasma nitriding on the corrosion properties of electroplated chromium/C45 mild steel were investigated using electrochemical characterization. The chromium plated samples were nitrided using a pulsed direct current glow discharge in an NH3 atmosphere. The polarization curve measurement results showed that the plasma nitrided samples exhibited more positive corrosion potentials (Ecorr), smaller corrosion currents (Icorr), and evident passivation when compared with unnitrided chromium plating/substrate system. The high value of Ecorr and low value of Icorr imply an improvement of the corrosion resistance of the coating/substrate system after plasma nitriding.