Corrosion resistance of nonequiatomic FeNiCrMnAlx high entropy alloys in hexamine as inhibitor in 3.5% NaCl

The corrosion performance of Fe35Ni20Cr12Mn(28-x)Al(5+x) high-entropy alloys (HEAs) with varying aluminum (Al) content (x = 0, 5, and 10 at.%) was studied in a 3.5% NaCl solution. Additionally, different concentrations of hexamine inhibitors (0.1, 0.2, and 0.3 g) were employed to enhance the corrosion resistance. Polarization measurements were conducted using a three-electrode electrochemical cell with a calomel reference electrode. Furthermore, polarization-dynamics experiments were carried out at room temperature with a scan rate of 0.33 mV/s. The findings indicated that hexamine improved the corrosion resistance of the investigated HEAs. However, the effectiveness of hexamine decreased as the Al content increased up to 15 at.%. In the case of Fe35Ni20Cr12Mn18Al15 HEA with 0.3 g hexamine, the surface exhibited the presence of iron oxides. These results were confirmed through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and elemental mapping, which revealed the distribution of elements under different conditions. The corrosion behavior of Fe35Ni20Cr12Mn(28-x)Al(5+x) high-entropy alloy (HEA) with different Al content was investigated in 3.5% NaCl with inhibitor hexamine. The corrosion resistance is worsened when the Al content increases and the Cr concentration decreases. Increased Al content resulted in increased Cr depletion, disintegration of the passive layer, and increased pitting and localized galvanized corrosion.image