Influence of Ti purification agent dosage on corrosion resistance of Fe-Cr-Ni alloys in molten chlorides

The severe corrosivity of molten chlorides can be mitigated by adding purification agents. Their addition dosage is a significant factor to impact the corrosion behavior of Fe-Cr-Ni alloys. This study investigates the influence of different Ti additions (0 wt%, 1 wt%, 3 wt%) on the corrosion behavior of SS 310, Incoloy 800H, and Inconel 617 alloys in molten MgCl 2 -NaCl-KCl at 700 °C under Ar atmosphere, with Ti serving as a reducing agent to purify the salts. The purification level of molten chlorides is increased with increasing Ti addition. The optimal addition of 1 wt% Ti reduces the corrosion depth by 85 % in SS 310, 87 % in 800H, and 98 % in 617 compared to 0 wt% Ti addition, which does not exert any direct influence to the alloy. When 3 wt% Ti is introduced, the excess Ti promotes a Ti-containing intermetallics diffusion layer formed on the alloy surfaces, of which structure becomes denser with increasing Ni contents within the alloys. The formation of thin diffusion layers with excessive Ti suggests that the destructive corrosion induced by the liquid metal as observed with excessive Mg addition can be effectively avoided. This work demonstrates that the optimal addition of Ti can effectively mitigate corrosion without directly affecting the alloys, while the thin diffusion layer formed with an excess of Ti could prevent the further corrosion of the alloys. • Increasing addition dosage of Ti increases the purification level of molten chlorides. • Appropriate dosage of Ti mitigates the alloy corrosion and avoid formation of intermetallics. • Excess Ti addition induces formation of a Ti-containing diffusion layer on alloy. • A denser diffusion layer is formed with increasing Ni content within the alloy. • The destructive corrosion caused by excess Mg can be effectively avoided by Ti addition.