Effect of ultrafine-grained structure and chromium addition on corrosion resistance of Ni-Cr-Al alloys

The present work aims to understand the various scientific aspects related to the corrosion behavior of the ultrafine-grained (UFG) and coarse-grained (CG) Ni-(10,20)Cr-10Al (wt%) alloys in 3.5 wt% NaCl solution based on the passive layer formation on the alloys. In this regard, UFG and CG Ni-(10, 20)Cr-10Al (wt%) alloys were synthesized and characterized. Results of corrosion studies reveal that the UFG structure of the alloys is favorable to enhance the corrosion performance due to their high grain boundary density, which provides nucleation sites for rapid and effective passivation of the alloys by the formation of external Cr2O3 layer instead of mixed oxides/ hydroxides. Besides, the Cr addition to the alloys also fosters the Cr-containing passive layer formation. The superior corrosion behavior of the UFG alloys is supported by scanning electron microscopy, electrochemical impedance spectroscopy, and Raman spectroscopy.