Corrosion evaluation of superalloys Haynes 282 and Inconel 718 in Hydrochloric acid

Corrosion susceptibility of Haynes 282 (HY282) and Inconel 718 (IN718) superalloys in hydrochloric acid (HCl) at ambient temperature was investigated using gravimetric and electrochemical techniques. In the gravimetric study, corrosion rate of the superalloys in 0.5 M, 0.75 M, and 1 M HCl for 72 days was evaluated using weight loss method. The concentration of metallic ions in the 1 M electrolyte after the immersion test was estimated using Atomic Absorption Spectroscopy and surface morphologies of the corroded superalloys was characterized using Optical microscopy and SEM/EDX. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky test were deployed to investigate the electrochemical properties of the passive film formed on both alloys in 1 M HCl. The results showed that HY282 exhibited a higher resistance to dissolution than IN718 in HCl owing to the presence of a more compact passive film with apparently less defect. This observation is explained in this communication based on compositional chemistry difference in both alloys.