Erosion–corrosion behaviour of nano-Al 2 O 3 reinforced Ni based alloying layer in acidic slurry flow

The aim of the present study was to study the effect of nano-Al₂O₃ particles on erosion–corrosion behaviour of Ni based alloying layer in acidic slurry flow. The nano-Al₂O₃ reinforced Ni based alloying layer was prepared by double glow plasma alloying on 316L stainless steel surface, where Ni/nano-Al₂O₃ was firstly predeposited by brush plating. AISI 316L stainless steel and single Ni based alloying layer without Ni/nano-Al₂O₃ interlayer were used as reference materials. Potentiodynamic polarisation, electrochemical impedance spectroscopy and mass loss techniques were applied to study the corrosion and erosion–corrosion behaviour of nano-Al₂O₃ reinforced Ni based alloying layer in acidic solution (10 wt-%HCl), acidic flow (10 wt-%HCl) and acidic slurry flow (10 wt-%HCl z 10 wt-% sand particles). Results of potentiodynamic polarisation indicated that the corrosion potentials E_corr of investigated materials were decreased and anodic current densities of investigated materials were increased under acidic flow condition when compared with that of obtained in static corrosion. Comparing with that obtained in acidic flow condition, a further decrease in corrosion potential E_corr and increase in anodic current density was observed under acidic slurry flow condition. Among the investigated materials, the corrosion current densities i_corr of nano-Al₂O₃ reinforced Ni based alloying layer were higher than that of Ni based alloying layer, but obviously lower than that of 316L stainless steel under three different conditions. The impedance measurements revealed that the size of semicircle diameters of investigated materials decreased continuously with rotating the samples in acidic flow and acidic slurry flow, comparing with that of obtained in static corrosion. The corrosion resistance of nano-Al₂O₃ reinforced Ni based alloying layer was lower than that of single alloying layer under three different conditions. Mass loss studies under acidic slurry flow conditions indicated that there was a threshold of rotational speed v_c, above which the mass loss of nano-Al₂O₃ reinforced Ni based alloying layer was apparently lower than that of single alloying layer. At 3·45 m s^–1 (v_c<3·45 m s^–1), the percentage of synergism of nano-Al₂O₃ reinforced Ni based alloying layer decreased by 17·26 and 16·76% as compared to that of AISI 316L stainless steel and single Ni based alloying layer.