Corrosion Resistance of Nickel-chromizing Layer Prepared by Pulse Single Power Plasma

A nickel-chromizing layer was formed on the surface of Q195 steel by pulse single power plasma. The surface morphology, phase composition and Cr-Ni content of nickel-chromizing layer were analyzed by XRD, SEM and EDS. The polarization curves of nickel-chromizing layer in 3.5% NaCl solution and 1 mol/L HNO3 solution were measured by electrochemical tests. The corrosion morphology was investigated and compared that of unprocessed samples of Q195 steel. The results show that the main phase composition of nickel-chromizing layer was Fe-Cr-Ni solid solution. The surface convex cellular organizations of nickel-chromizing layer were dense. The composition of the surface was Cr 16.9%, Ni 48.16%, and iron remaining. In NaCl solution, the surface of unprocessed sample of Q195 steel was corroded seriously resulted in holes, but the surface of nickel-chromizing layer only showed minor localized corrosion and produced some plaques. In HNO3 solution, the unprocessed sample of Q195 steel showed serious surface corrosion, but it was almost not corrode in the nickel-chromizing layer, i, e., the corrosion resistance of the latter was much higher than that of the former.