A comparative study on the high temperature corrosion of TP347H stainless steel, C22 alloy and laser-cladding C22 coating in molten chloride salts

Highlights: • Two KCl and NaCl mixtures simulated molten salt corrosion of biomasses combustion. • The corrosivity of forestry and agricultural biomasses was comparatively studied. • Corrosion of TP347H, C22 alloy and C22 coating was carried out at 450–750 °C. • Laser-cladding C22 coating exhibited least performance degradation. • Microstructures, compositions and corrosion mechanisms were strongly interrelated. - Abstract: Isothermal corrosion of TP347H (A1), C22 alloy (A2) and laser-cladding C22 coating (A3) was evaluated by mass loss measurements in molten alkali chloride salts at 450–750 °C. Corrosion mechanisms were characterised by scanning electron microscopy, optical microscopy and X-ray diffraction. A3 exhibited superior corrosion resistance, followed by A2, which results from alloying elements, refined microstructure and Cr–O (CrOx), Co(Fe, Cr)2O4 in the corrosion scale. Severe intergranular corrosion caused failure of A1, slight intergranular corrosion happened in A2 but none in A3. Fe-rich oxides were main products of A1 while NiO of A2 and A3 with Cr2O3 and Mo-containing compositions