Corrosion Behavior of Stainless Steels and Nickel-Based Alloys in Acetic Acid Solutions Containing Bromide Ions Available to Purchase

The immersion test method, potentiodynamic cyclic anodic polarization, scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS) techniques were used to study corrosion behavior of stainless steels (SS) and nickel-based alloys in acetic acid (CH₃COOH; HAc) solutions containing bromide ions. In 50% HAc solution containing 0.29 M Br ^– at 80°C, materials suffered serious general corrosion. The corrosion rate of UNS N02200 reached 2.94 mm/y, and UNS S31304 SS had a rate of 2.05 mm/y. Under this condition, UNS S31803 duplex SS experienced very serious pitting. Anodic polarization test results showed that UNS N10276 had excellent pitting resistance, but UNS N02200 SS and UNS S31304 SS easily suffered pitting attack. The alloying element nickel did not resist corrosion by itself, but with the presence of chromium and molybdenum it had good corrosion resistance. The elements in the surface film were analyzed by XPS. It was found that chromium and molybdenum could form the protective films of chromic oxide (Cr₂O₃) and molybdenum dioxide (MoO₂), protecting materials from the attack of aggressive ions. Pit morphologies were inspected by SEM after anodic polarization treatment and were consistent with the electrochemical test results.