Electrochemical corrosion behaviour of ZrB2–Inconel 718 composites

The electrochemical corrosion behaviour of ZrB 2 –Inconel 718 composites fabricated by freeze casting followed by pressureless spark plasma sintering was investigated in a 0.5 M NaCl solution and compared with that of the reference monolithic ZrB 2 and commercial Inconel 718. Electrochemical techniques, including open‑circuit potential measurements, potentiodynamic polarisation, and electrochemical impedance spectroscopy, were used alongside microstructural characterisation by optical microscopy and scanning electron microscopy coupled with energy‑dispersive X‑ray spectroscopy. It was found that the composites exhibited low corrosion current densities and a passive behaviour over a given potential range, indicating a stable electrochemical response under the studied conditions. Corrosion was primarily localised within Fe‑rich and Ni‑rich regions depleted in Cr, whereas Cr‑rich areas and ceramic ZrB 2 phases remained comparatively stable. Increasing the Inconel 718 fraction led to a slight improvement in the electrochemical response, as evidenced by higher values of both impedance modulus and charge‑transfer resistance. Surface analysis following prolonged immersion revealed that degradation was not uniform across the exposed surface, but rather confined to localised regions associated with the formation of Fe‑rich corrosion products. Overall, although the composites exhibited lower corrosion resistance than the reference materials, they remain sufficiently corrosion-resistant for applications in such environments.