Effect of Al on Corrosion Behavior in 3.5%NaCl Solution of Al<sub>x</sub>CoCrFeNi High Entropy Alloys

The high entropy alloys have attracted the interest of material scientists due to theirspecial mechanical properties and a very good corrosion behavior. The corrosion resistance is provided by the formation of a passive, thin and compact oxide film that prevents the chemical dissolution of the metallic matrix. The effect of aluminum in AlxCrFeCoNi high entropy alloys (with x = 1; 1.5 and 2) that were obtained by electric arc melting under argon atmosphere has been studied in the paper. In order to understand the processes involved in metal corrosion, the alloys have been tested by polarization resistance method in 3.5% NaCl solution and main corrosion parameters have been analyzed (i.e. corrosion potential; corrosion current density; corrosion rate and polarization resistance). The surfaces of the corroded samples were examined by scanning electron microscopy to estimate the effect of the chemical composition on corrosion resistance. The corrosion tests have shown that the corrosion resistance of the HEA decreases by increasing the aluminum content from about 15 at.% to 32 at. % Al and reducing the chromium content from 28 at. % to 18 at.% Cr.