Effect of rare earth oxide nano-additives on the corrosion behavior of Fe-based hardfacing alloys in acid, near-neutral and alkaline 3.5 wt.% NaCl solutions

In this paper, effect of rare earth oxide nano-additives on the corrosion behavior of Fe-based hardfacing alloys was studied. The corrosive solutions were 3.5   wt.% NaCl   +   0.01   mol/L HCl solution, 3.5   wt.% NaCl solution and 3.5   wt.% NaCl   +   0.01   mol/L NaOH solution. The deep-etched microstructure of the hardfacing alloys was observed. The potentiodynamic polarization curves and electrochemical impedance spectra were used to study the corrosion behavior of the hardfacing alloys. The polarization test results showed that nano-additives shifted the corrosion potentials of the hardfacing alloys towards the noble direction in corrosive solutions. The values of the equivalent circuit elements for the impedance spectra of the hardfacing alloys indicated that nano-additives increased the corrosion resistance of the hardfacing alloys. When the content of nano-additives was 0.3   wt.%, the hardfacing alloy possessed the maximum charge transfer resistance in acid NaCl solution. The hardfacing alloy with 0.6   wt.% nano-additives had the maximum charge transfer resistance in near-neutral and alkaline NaCl solutions. The change in volume fraction of the primary and eutectic carbides and refinement of primary carbide influenced the corrosion behavior of the hardfacing alloys.