Surface-engineered MWCNT-based ethylene glycol–water coolants for corrosion protection of multi-metal automotive components

Carbon-nanotube-based coolants offer enhanced heat-transfer potential, but their corrosion compatibility with metallic cooling components remains a concern. This study investigates the corrosion behaviour of aluminium, copper, and cast iron in ethylene glycol–water coolant containing acid-functionalized multi-walled carbon nanotubes (MWCNTs) at 0.125–0.5 wt%. Potentiodynamic polarization, SEM–EDX, and FTIR were employed to evaluate corrosion resistance and surface characteristics. MWCNT addition reduced corrosion current density and corrosion rate across all three metals. At 0.25 wt%, copper corrosion decreased from 0.331 to 0.099 mm/yr (≈70% inhibition), while cast-iron corrosion decreased from 23.5 to 20.3 mm/yr. Aluminium exhibited an increase in pitting potential from + 420 to + 670 mV, accompanied by a reduction in corrosion rate from 0.309 to 0.295 mm/yr. SEM–EDX revealed a carbon-enriched protective surface layer, while polarization analysis indicated predominantly cathodic inhibition for aluminium and cast iron and mixed-to-anodic inhibition for copper. Surface coverage followed Langmuir-type adsorption behaviour. These findings demonstrate the potential of functionalized MWCNTs to improve corrosion protection in glycol-based coolants for automotive, marine, and solar-thermal applications.