Corrosion Behavior of As-Cladding Al_0.8CrFeCoNiCu_0.5Si_x High Entropy Alloys in 3.5% NaCl Solution

The corrosion behavior of Al_0.8CrFeCoNiCu_0.5Si_x (x=0, 0.2, 0.3) high-entropy alloy laser cladding coatings in a 3.5% NaCl solution was investigated using polarization tests, impedance spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. As the Si content increased, the over-passivation potential and the width of the passivation zone for the Al_0.8CrFeCoNiCu_0.5Six coating expanded, while the corrosion current density tended to decrease, enhancing the stability of the passivation film and the corrosion resistance of the coating. The Al_0.8CrFeCoNiCu_0.5 coating underwent selective corrosion, with some pitting corrosion distribution showing no apparent regularity. The Al_0.8CrFeCoNiCu_0.5Si_0.2 coating exhibited a distinct grain profile with a tendency towards intergranular corrosion. The aggregation of Cu-rich and Al-Ni intergranular phases in the eutectic structure led to preferential erosion at the grain boundaries by corrosion ions in the Al_0.8CrFeCoNiCu_0.5Si_0.2 coating. The Al_0.8CrFeCoNiCu_0.5Si_0.3 coating presented corrosion pits, although their distribution did not display apparent regularity. The Al_0.8CrFeCoNiCu_0.5Si_x high-entropy alloy coating demonstrates superior corrosion resistance in solution compared to 5083 aluminum alloy.

Keywords:
High entropy alloy; Laser cladding; Corrosion resistance; Corrosion behavior