Corrosion of Corrosion-Resistant and High-Temperature Nickel-Based Alloys in Chloroaluminate Melts

The corrosion resistance of Haynes 230, Hastelloy S and X high-temperature alloys and Hastelloy N, B-3, G-35, C-2000 corrosion-resistant alloys was investigated in a wide temperature range (450-650 °C) in fused KCl-AlCl3 mixtures. It was found that the mechanisms of corrosion of high-temperature alloys and corrosion-resistant alloys in KCl-AlCl3 based melts are different. At a critical temperature phase structure of the high-temperature alloys changes after contact with chloroaluminate melts resulting in formation of intermetallic or carbon-containing phases along the grain boundaries that result in increasing strength of the alloys but initiate intense intergranular corrosion. The structural changes in most of the corrosion-resistant alloys take place at higher temperatures but they also can cause structural changes in the materials. It was shown that both types of alloys undergo intergranular corrosion up to the critical conditions. Formation of different secondary phases was detected and their influence on the corrosion processes mechanism is analyzed.